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Archive for the ‘Medical Device Therapies for Altzheimer’s Disease’ Category


Recent comprehensive review on the role of ultrasound in breast cancer management

Writer, reporter and curator: Dror Nir, PhD

The paper below by R Hooley is a beautifully written review on how ultrasound could (and should) be practiced to better support breast cancer screening, staging, and treatment. The authors went as well into the effort of describing the benefits from combining ultrasonography with the other frequently used imaging modalities; i.e. mammography, tomosynthesis and MRI. Post treatment use of ultrasound is not discussed although this is a major task for this modality.

I would like to recommend giving attention to two very small (but for me very important) paragraphs: “Speed of Sound Imaging” and “Lesion Annotation”

Enjoy…

Breast Ultrasonography: State of the Art

Regina J. Hooley, MDLeslie M. Scoutt, MD and Liane E. Philpotts, MD

Department of Diagnostic Radiology, Yale University School of Medicine, 333 Cedar St, PO Box 208042, New Haven, CT 06520-8042.

Address correspondence to R.J.H. (e-mail: regina.hooley@yale.edu).

Ultrasonography (US) has become an indispensable tool in breast imaging. Breast US was first introduced in the 1950s by using radar techniques adapted from the U.S. Navy (1). Over the next several decades, US in breast imaging was primarily used to distinguish cystic from solid masses. This was clinically important, as a simple breast cyst is a benign finding that does not require further work-up. However, most solid breast lesions remained indeterminate and required biopsy, as US was not adequately specific in differentiating benign from malignant solid breast masses. However, recent advances in US technology have allowed improved characterization of solid masses.

In 1995, Stavros et al (2) published a landmark study demonstrating that solid breast lesions could be confidently characterized as benign or malignant by using high-resolution grays-cale US imaging. Benign US features include few (two or three) gentle lobulations, ellipsoid shape, and a thin capsule, as well as a homogeneously echogenic echotexture. Malignant US features include spiculation, taller-than-wide orientation, angular margins, microcalcifications, and posterior acoustic shadowing. With these sonographic features, a negative predictive value of 99.5% and a sensitivity of 98.4% for the diagnosis of malignancy were achieved. These results have subsequently been validated by others (3,4) and remain the cornerstone of US characterization of breast lesions today. These features are essential in the comprehensive US assessment of breast lesions, described by the Breast Imaging and Reporting Data System (BI-RADS) (5).

US is both an adjunct and a complement to mammography. Advances in US technology include harmonic imaging, compound imaging, power Doppler, faster frame rates, higher resolution transducers, and, more recently, elastography and three-dimensional (3D) US. Currently accepted clinical indications include evaluation of palpable abnormalities and characterization of masses detected at mammography and magnetic resonance (MR) imaging. US may also be used as an adjuvant breast cancer screening modality in women with dense breast tissue and a negative mammogram. These applications of breast US have broadened the spectrum of sonographic features currently assessed, even allowing detection of noninvasive disease, a huge advance beyond the early simplistic cyst-versus-solid assessment. In addition, US is currently the primary imaging modality recommended to guide interventional breast procedures.

The most subtle US features of breast cancers are likely to be best detected by physicians who routinely synthesize findings from multiple imaging modalities and clinical information, as well as perform targeted US to correlate with lesions detected at mammography or MR imaging. Having a strong understanding of the technical applications of US and image optimization, in addition to strong interpretive and interventional US skills, is essential for today’s breast imager.

 

Optimal Imaging Technique

US is operator dependent, and meticulous attention to scanning technique as well as knowledge of the various technical options available are imperative for an optimized and accurate breast US examination. US is an interactive, dynamic modality. Although breast US scanning may be performed by a sonographer or mammography technologist, the radiologist also benefits greatly from hands-on scanning (Fig 1). Berg et al (6) demonstrated that US interpretive performance was improved if the radiologist had direct experience performing breast US scanning, including rescanning after the technologist. Real-time scanning also provides the opportunity for thorough evaluation of lesions and permits detailed lesion analysis compared with analyzing static images on a workstation. Subtle irregular or indistinct margins, artifacts, and architectural distortions may be difficult to capture on static images. Real-time scanning also allows the operator to assess lesion mobility, location, and relationship to adjacent structures and allows direct assessment of palpable lesions and other clinical findings. Moreover, careful review of any prior imaging studies is imperative to ensure accurate lesion correlation.

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The US examination is generally well tolerated by the patient. Gentle but firm transducer pressure and optimal patient positioning are essential, with the patient’s arm relaxed and flexed behind the head. Medial lesions should generally be scanned in the supine position, and lateral lesions, including the axilla, should usually be scanned with the patient in the contralateral oblique position. This allows for elimination of potential artifact secondary to inadequate compression of breast tissue.

 

Gray-Scale Imaging

Typical US transducers used in breast imaging today have between 192 and 256 elements along the long axis. When scanning the breast, a linear 12–5-MHz transducer is commonly used. However, in small-breasted women (with breast thickness < 3 cm) or when performing targeted US to evaluate a superficial lesion, a linear 17–5-MHz transducer may be used. Such high-frequency transducers provide superb spatial and soft-tissue resolution, permitting substantially improved differentiation of subtle shades of gray, margin resolution, and lesion conspicuity in the background of normal breast tissue (Fig 2). However, the cost of such a high insonating frequency is decreased penetration due to attenuation of the ultrasound beam, making visualization of deep posterior tissue difficult (ie, greater than 3 cm in depth by using a linear 17–5-MHz transducer or greater than 5 cm in depth by using a linear 12–5-MHz transducer).

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During the initial US survey of the region of interest in the breast, the depth should be set so that the pectoralis muscle is visualized along the posterior margin of the field of view. Initial gain settings should be adjusted so that fat at all levels is displayed as a midlevel gray. Simple cysts are anechoic. Compared with breast fat, most solid masses are hypoechoic, while the skin, Cooper ligaments, and fibrous tissue are echogenic. Time gain compensation, which adjusts image brightness at different depths from the skin to compensate for attenuation of the ultrasound beam as it penetrates into the breast tissue, may be set manually or, with appropriate equipment, may be adjusted automatically during real-time scanning or even during postprocessing of the image.

When searching for a lesion initially identified at mammography or MR imaging, careful correlation with lesion depth and surrounding anatomic structures is imperative. Lesion location may be affected by the patient’s position, which differs during mammography, US, and MR imaging examinations. Attention to surrounding background tissue may assist in accurate lesion correlation across multiple modalities. If a mass identified at mammography or MR imaging is surrounded entirely by fat or fibroglandular tissue, at US it should also be surrounded by hypoechoic fat or echogenic fibroglandular tissue, respectively. Similarly, careful attention to the region of clinical concern is necessary when scanning a palpable abnormality to ensure that the correct area is scanned. The examiner should place a finger on the palpable abnormality and then place the transducer directly over the region. Occasionally, the US examination may be performed in the sitting position if a breast mass can only be palpated when the patient is upright.

After a lesion is identified, or while searching for a subtle finding, the depth or field of view may be adjusted as needed. The depth should be decreased to better visualize more superficial structures or increased to better visualize deeper posterior lesions. The use of multiple focal zones also improves resolution at multiple depths simultaneously and should be used, if available. Although this reduces the frame rate, the reduction is typically negligible when scanning relatively superficial structures within the breast. If a single focal zone is selected to better evaluate a single lesion, the focal zone should be centered at the same level as the area of interest or minimally posterior to the area of interest, for optimal visualization.

 

Spatial Compounding, Speckle Reduction, and Harmonic Imaging

Spatial compound imaging and speckle reduction are available on most high-end US units and should be routinely utilized throughout the breast US examination. Unlike standard US imaging, in which ultrasound pulses are transmitted in a single direction perpendicular to the long axis of the transducer, spatial compounding utilizes electronic beam steering to acquire multiple images obtained from different angles within the plane of imaging (79). A single composite image is then obtained in real-time by averaging frames obtained by ultrasound beams acquired from these multiple angles (10). Artifactual echoes, including speckle and other spurious noise, as well as posterior acoustic patterns, including posterior enhancement (characteristic of simple cysts) and posterior acoustic shadowing (characteristic of some solid masses), are substantially reduced. However, returning echoes from real structures are enhanced, providing improved contrast resolution (9) so that ligaments, edge definition, and lesion margins, including spiculations, echogenic halos, posterior and lateral borders, as well as microcalcifications, are better defined. Speckle reduction is a real-time postprocessing technique that also enhances contrast resolution, improves border definition, is complementary to spatial compounding, and can be used simultaneously.

When a lesion is identified, harmonic imaging may also be applied—usually along with spatial compounding—to better characterize a cyst or a subtle solid mass. The simultaneous use of spatial compounding and harmonic imaging may decrease the frame rate, although this usually does not impair real-time evaluation. Harmonic imaging relies on filtering the multiple higher harmonic frequencies, which are multiples of the fundamental frequencies. All tissue is essentially nonlinear to sound propagation and the ultrasound pulse is distorted as it travels through breast tissue, creating harmonic frequencies (9). The returning ultrasound signal therefore contains both the original fundamental frequency and its multiples, or harmonics. Harmonic imaging allows the higher harmonic frequencies to be selected and used to create the gray-scale images (89). Lower-frequency superficial reverberation echoes are thereby reduced, allowing improved characterization of simple cysts (particularly if small) through the elimination of artifactual internal echoes often seen in fluid. Harmonic imaging also improves lateral resolution (10) and may also improve contrast between fatty tissue and subtle lesions, allowing better definition of subtle lesion margins and posterior shadowing (Fig 3).

 

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Speed of Sound Imaging

Conventional US systems set the speed of sound in tissue at a uniform 1540 m/sec (10). However, the speed of sound in tissues of different composition is variable and this variability may compromise US image quality. Breast tissue usually contains fat, and the speed of sound in fat, of approximately 1430–1470 m/sec, is slower than the assumed standard (11). Accurate speed of sound imaging, in which the US transducer may be optimized for the presence of fat within breast tissue, has been shown to improve lateral resolution (12). Additionally, it can be used to better characterize tissue interfaces, lesion margins, and microcalcifications (13) and may also be useful to identify subtle hypoechoic lesions surrounded by fatty breast tissue. Speed of sound imaging is available on most high-end modern US units and is an optional adjustment, depending on whether predominately fatty, predominately dense, or mixed breast tissue is being scanned.

 

 Lesion Annotation

When a mass is identified and the US settings are optimized, the mass should be scanned with US “sweeps” through the entire lesion in multiple planes. Images of the lesion in the radial and antiradial views should be captured and annotated with “right” or “left,” clock face position, and centimeters from the nipple. Radial and anti-radial scanning planes are preferred over standard transverse and sagittal scanning planes because scanning the breast along the normal axis of the mammary ducts and lobar tissues allows improved understanding of the site of lesion origin and better visualization of ductal extension and helps narrow the differential diagnosis (14). Images should be captured with and without calipers to allow margin assessment on static images. Lesion size should be measured in three dimensions, reporting the longest horizontal diameter first, followed by the anteroposterior diameter, then the orthogonal horizontal.

 

 Extended-Field-of-View Imaging

Advanced US technology permits extended-field-of-view imaging beyond the footprint of the transducer. By using a freehand technique, the operator slides the transducer along the desired region to be imaged. The resultant images are stored in real-time and, by applying pattern recognition, a single large-field-of-view image is obtained (7). This can be helpful in measuring very large lesions as well as the distance between multiple structures in the breast and for assessing the relationship of multifocal disease (located in the same quadrant as the index cancer or within 4–5 cm of the index cancer, along the same duct system) and/or multicentric disease (located in a different quadrant than the index cancer, or at a distance greater than 4–5 cm, along a different duct system).

 

 Doppler US

Early studies investigating the use of color, power, and quantitative spectral Doppler US in the breast reported that the presence of increased vascularity, as well as changes in the pulsatility and resistive indexes, showed that these Doppler findings could be used to reliably characterize malignant lesions (15,16). However, other investigators have demonstrated substantial overlap of many of these Doppler characteristics in both benign and malignant breast lesions (17). Gokalp et al (18) also demonstrated that the addition of power Doppler US and spectral analysis to BI-RADS US features of solid breast masses did not improve specificity. While the current BI-RADS US lexicon recommends evaluation of lesion vascularity, it is not considered mandatory (5).

Power Doppler is generally more sensitive than color Doppler to low-flow volumes typical of breast lesions. Light transducer pressure is necessary to prevent occlusion of slow flow owing to compression of the vessel lumen. Currently both power and color Doppler are complementary tools to gray-scale imaging, and power Doppler may improve sensitivity in detecting malignant breast lesions (18,19). Demonstration of irregular branching central or penetrating vascularity within a solid mass raises suspicion of malignant neovascularity (20). Recently, the parallel artery and vein sign has been described as a reliable feature that has the potential to enable prediction of benignity in solid masses so that biopsy may be avoided. In a single study, a paired artery and vein was present in 13.2% of over 1000 masses at US-guided CNB and although an infrequent finding, the specificity for benignity was 99.3% and the false-negative rate was only 1.4%, with two malignancies among 142 masses in which the parallel artery and vein sign was identified (21).

Color and power Doppler US are also useful to evaluate cysts and complex cystic masses that contain a solid component. High-grade invasive cancer and metastatic lymph nodes may occasionally appear anechoic. Demonstration of flow within an otherwise simple appearing cyst, a complicated cyst, or a complex mass confirms the presence of a suspicious solid component, which requires biopsy. In addition, twinkle artifact seen with color Doppler US is useful to identify a biopsy marker clip or subtle echogenic microcalcifications (Fig 4). This Doppler color artifact occurs secondary to the presence of a strong reflecting granular surface and results in a rapidly changing mix of color adjacent to and behind the reflector (22). Care must be taken to avoid mistaking twinkle artifact for true vascular flow and, if in doubt, a spectral Doppler tracing can be obtained, as a normal vascular waveform will not be seen with a twinkle artifact.

 

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Elastography

At physical examination, it has long been recognized that malignant tumors tend to feel hard when compared with benign lesions. US elastography can be used to measure tissue stiffness with the potential to improve specificity in the diagnosis of breast masses. There are two forms of US elastography available today: strain and shear wave. With either technique, acoustic information regarding lesion stiffness is converted into a black-and-white or color-scaled image that can also be superimposed on top of a B-mode gray-scale image.

Strain elastography requires gentle compression with a US probe or natural motion (such as heart beat, vascular pulsation, or respiration) and results in tissue displacement, or strain. Strain (ie, tissue compression and motion) is decreased in hard tissues compared with soft tissue (23). The information obtained with strain elastography provides qualitative information, although strain ratios may be calculated by comparing the strain of a lesion to the surrounding normal tissue. Benign breast lesions generally have lower ratios in comparison to malignant lesions (24,25).

Shear-wave elastography is based on the principle of acoustic radiation force. With use of light transducer pressure, transient automatic pulses can be generated by the US probe, inducing transversely oriented shear waves in tissue. The US system captures the velocity of these shear waves, which travel faster in hard tissue compared with soft tissue (26). Shear-wave elastography provides quantitative information because the elasticity of the tissue can be measured in meters per second or in kilopascals, a unit of pressure.

Elastography features such as strain ratios, size ratios, shape, homogeneity, and maximum lesion stiffness may complement conventional US in the analysis of breast lesions. Malignant masses evaluated with elastography tend to be more irregular, heterogeneous, and typically appear larger at elastography than at grayscale imaging (Fig 5) (27,28). Although malignant lesions generally also exhibit maximum stiffness greater than 80–100 kPa (28,29), caution is necessary when applying these numerical values to lesion analysis. Berg et al (28) reported three cancers among 115 masses with maximum stiffness between 20 and 30 kPa, for a 2.6% malignancy rate; 25 cancers among 281 masses with maximum stiffness between 30 and 80 kPa, for an 8.9% malignancy rate; and 61 cancers among 153 masses with maximum stiffness between 80 and 160 kPa, for a 39.9% malignancy rate (28). Invasive cancers with high histologic grade, large tumor size, nodal involvement, and vascular invasion have also been shown to be significantly correlated with high mean stiffness at shear-wave elastography (30).

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Elastography may be useful in improving the specificity of US evaluation of BI-RADS 3 and 4A lesions, including complicated cysts. Berg and colleagues (28) showed that by using qualitative shear-wave elastography and color assessment of lesion stiffness, oval shape, and a maximum elasticity value of less than 80 kPa, unnecessary biopsy of low-suspicion BI-RADS 4A masses could be reduced without a significant loss in sensitivity. Several investigators have proposed a variety of imaging classifications using strain elastography, mostly based on the color pattern (27,31,32). A “bull’s eye” artifact has also been described as a characteristic feature present in benign breast cysts, which may appear as a round or oval lesion with a stiff rim associated with two soft spots, one located centrally and the other posteriorly (33).

Despite these initial promising studies regarding the role of US elastography in the analysis of breast lesions, limitations do exist. Strain and shear-wave elastography are quite different methods of measuring breast tissue stiffness, and the application of these methods varies across different commercial manufacturers. Inter- and intraobserver variability may be relatively high because the elastogram may be affected by differences in degree and method of compression. With strain elastography, a quality indicator that is an associated color bar or numerical value may be helpful to ensure proper light compression. Shear-wave elastography has been shown to be less operator-dependent, as tissue compression is initiated by the US probe in a standard, reproducible fashion (34) and only light transducer pressure is necessary. In addition, there is currently no universal color-coding standard and, depending on the manufacturer and/or operator preference, stiff lesions may be arbitrarily coded to appear red while soft lesions appear blue, or vice versa. Some elastography features such as the “bull’s eye” artifact are only seen on specific US systems. Lesions deeper than 2 cm are less accurately characterized by means of elastography. Moreover, one must be aware that soft cancers and hard benign lesions exist. Therefore, careful correlation of elastography with B-mode US features and mammography is essential. Future studies and further technical advances, including the creation of more uniformity across different US manufacturers, will ultimately determine the usefulness of elastography in clinical practice.

Three-dimensional US

Both handheld and automated high-resolution linear 3D transducers are now available for use in breast imaging. With a single pass of the ultrasound beam, a 3D reconstructed image can be formed in the coronal, sagittal, and transverse planes, potentially allowing more accurate assessment of anatomic structures and tumor margins (Fig 6). Few studies regarding the performance of 3D US in the breast exist, but a preliminary study demonstrated improved characterization of malignant lesions (35). Automated supine whole-breast US using 3D technology is now widely available for use in the screening setting (see section on screening breast US). Three-dimensional US may also be used in addition to computed tomography for image-guided radiation therapy (36) and has a potential role in assessing tumor response to neoadjuvant chemotherapy.

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US Features of Benign and Malignant Breast Lesions

Cysts

Although for many years the main function of breast US was to differentiate cysts from solid masses, this differentiation can at times be problematic, particularly if the lesion is small or located deep in the breast. Simple cysts are defined as circumscribed, anechoic masses with a thin imperceptible wall and enhanced through transmission (provided spatial compounding is not used). By convention, simple cysts may also contain up to a single thin septation. Simple cysts are confidently characterized with virtually 100% accuracy at US (14,37), provided that they are not very small (< 5 mm in size) or not located in deep tissue. Complicated cysts are hypoechoic with no discernable Doppler flow, contain internal echoes, and may also exhibit indistinct margins, and/or lack posterior acoustic enhancement. Clustered microcysts consist of a cluster of tiny (<2–3 mm in size) anechoic foci with thin (< 0.5 mm in thickness) intervening septations.

Complicated cysts are very common sonographic findings and the majority are benign. In multiple studies, which evaluated over 1400 complicated cysts and microcysts, the malignancy rate ranged from 0% to 0.8% (3844). Most complicated cysts and clustered microcysts with a palpable or mammographic correlate are classified as BI-RADS 3 and require short-interval imaging follow-up or, occasionally, US-guided aspiration. However, in the screening US setting, if multiple and bilateral complicated and simple cysts are present (ie, at least three cysts with at least one cyst in each breast), these complicated cysts can be assessed as benign, BI-RADS 2, requiring no additional follow-up (38).

Complicated cysts should never demonstrate internal vascularity at color Doppler interrogation. The presence of a solid component, mural nodule, thickened septation, or thickened wall within a cystic mass precludes the diagnosis of a benign complicated cyst. These complex masses require biopsy, as some cancers may have cystic components. The application of compound imaging and harmonics, color Doppler, and potentially elastography may help differentiate benign complicated cysts from malignant cystic-appearing masses and reduce the need for additional follow-up or biopsy.

Solid Masses

Sonographic features of benign-appearing solid masses include an oval or ellipsoid shape, “wider-than-tall” orientation parallel to the skin, circumscribed margins, gentle and smooth (less than three) lobulations, as well as absence of any malignant features (2,45) (Fig 2b). Lesions with these features are commonly fibroadenomas or other benign masses and can often be safely followed, even if the mass is palpable (4648). Malignant features of solid masses include spiculations, angular margins, marked hypoechogenicity, posterior acoustic shadowing, microcalcifications, ductal extension, branching pattern, and 1–2-mm microlobulations (2,45) (Figs 1b,56). These are also often taller-than-wide lesions with a nonparallel orientation to the skin and may occasionally be associated with thickened Cooper ligaments and/or or skin thickening. Most cancers have more than one malignant feature, spiculation being the most specific and angular margins the most common (2).

There is, however, considerable overlap between these benign and malignant US features and careful scanning technique, as well as direct correlation with mammography, is essential. For example, some high-grade invasive ductal carcinomas with central necrosis, as well as the well-differentiated mucinous and medullary subtypes, may present as circumscribed, oval, hypoechoic masses that may look like complicated cysts with low-level internal echoes at US. Benign focal fibrous breast tissue or postoperative scars can appear as irregular shadowing masses on US images. Furthermore, while echogenic lesions are often benign and frequently represent lipomas or fibrous tissue, echogenic cancers do rarely occur (Figs 78) (49,50). The presence of a single malignant feature, despite the presence of multiple benign features, precludes a benign classification and mandates biopsy, with the exception of fat necrosis and postoperative scars exhibiting typical benign mammographic features. Likewise, a mass with a benign US appearance should be biopsied if it exhibits any suspicious mammographic features.

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 Ductal Carcinoma in Situ

Ductal carcinoma in situ (DCIS) is characteristically associated with microcalcifications detected at mammography, but may also be detected at US since they are often associated with a subtle hypoechoic mass, which may indicate an invasive mammographically occult component. US features associated with DCIS most commonly include a hypoechoic mass with an irregular shape, microlobulated margins, no posterior acoustic features, and no internal vascularity. Ductal abnormalities, intracystic lesions, and architectural distortions may also be present (5153). Noncalcified DCIS manifesting as a solid mass at US is more frequently found in non–high-grade than high-grade DCIS, which is more often associated with microcalcifications and ductal changes (54). US can depict microcalcifications, particularly those in clusters greater than 10 mm in size and located in a hypoechoic mass or a ductlike structure (Fig 9) (55). Malignant calcifications are more likely to be detected sonographically than are benign calcifications, which may be obscured by surrounding echogenic breast tissue (55,56). Although US is inferior to mammography in the detection of suspicious microcalcifications, the main benefit of US detection of DCIS is to identify the invasive component and guide biopsy procedures.

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Breast US in Clinical Practice

Current indications for breast US as recommended by the American College of Radiology Practice Guidelines include the evaluation of palpable abnormalities or other breast symptoms, assessment of mammographic or MR imaging–detected abnormalities, and evaluation of breast implants (57). Additionally, US is routinely used for guidance during interventional procedures, treatment planning for radiation therapy, screening in certain groups of women, and evaluation of axillary lymph nodes. Much literature has been written on these uses and a comprehensive discussion is beyond the scope of this article. A few important and timely topics, however, will be reviewed.

 

 

BI-RADS US

The BI-RADS US lexicon was introduced in 2003, and subsequently, there have been several studies assessing the accuracy of BI-RADS US classification of breast lesions. Low to moderate interobserver agreement has been found in the description of margins (especially noncircumscribed margins), echogenicity, and posterior acoustic features. Abdullah et al (58) reported low interobserver agreement especially for small masses and for malignant masses. Given the importance of margin analysis in the characterization of benign and malignant lesions, this variability is potentially problematic. Studies have also shown variable results in the use of the final assessment categories. In clinical settings, Raza et al (46) showed inconsistent use of the BI-RADS 3 (probably benign) category in 14.0% of cases when biopsy was recommended. Abdullah et al also demonstrated fair and poor interobserver agreement for BI-RADS 4 (suspicious for malignancy) a, b, and c subcategories (58). However, Henig et al (59) reported more promising results, with malignancy rates in categories 3, 4, and 5 to be similar to those seen with mammographic categorization (1.2%, 17%, and 94%, respectively).

 

 Evaluation of Mammographic Findings

Targeted US is complementary to diagnostic mammography because of its ability to differentiate cystic and solid lesions.US is also useful in the work up of subtle asymmetries, as it can help identify or exclude the presence of an underlying mass. True hypoechoic lesions can often be differentiated from prominent fat lobules by scanning in multiple planes, because true lesions usually do not blend or elongate into adjacent tissue. With the introduction of digital breast tomosynthesis for mammographic imaging, US will play yet another important role. As mammographic lesions can often be detected, localized, and have adequate margin assessment on 3D images, patients with lesions detected on digital breast tomosynthesis images at screening may often be referred directly to US, avoiding additional mammographic imaging and its associated costs and radiation exposure (Fig 10). This will place an even greater importance on high-quality US.

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Evaluation of the Symptomatic Patient:Palpable Masses, Breast Pain, and Nipple Discharge

US is essential in the evaluation of patients with the common clinical complaint of either a palpable mass or focal persistent breast pain. Unlike focal breast pain, which may be occasionally associated with benign or malignant lesions, diffuse breast pain (bilateral or unilateral), as well as cyclic breast pain, requires only clinical follow-up, as it is usually physiologic with an extremely low likelihood of malignancy (60,61). In patients with isolated focal breast pain, the role of sonography may be limited to patient reassurance (61). In women younger than 30 years of age, with a palpable lump or focal breast pain, US is the primary imaging test, with a sensitivity and negative predictive value of nearly 100% (62). Symptomatic women older than 30 years usually require both US and mammography, and in these patients, the negative predictive value approaches 100% (63,64). Lehman et al (65) demonstrated that in symptomatic women aged 30–39 years, the risk of malignancy was 1.9% and the added value of adjunct mammography in addition to US was low. Identification of a benign-appearing solid lesion at US in a symptomatic woman can negate the need for needle biopsy, as many of these masses can safely be monitored with short-interval follow-up US (4648), usually performed at 6 months. A suspicious mass identified at US can promptly undergo biopsy with US guidance.

US can also be used as an alternative or an addition to ductography in patients who present with unilateral, spontaneous bloody, clear, or serosanguinous nipple discharge (66). Among women with worrisome nipple discharge, ductography can demonstrate an abnormality in 59%–82% of women (67,68), MR imaging may demonstrate a suspicious abnormality in 34% of women (68), and US has been shown to demonstrate a subareolar mass or an intraductal mass or filling defect in up to 14% of women (67). If US can be used to identify a retroareolar mass or an intraductal mass, US-guided biopsy can be performed and ductography may be avoided (Fig 11). US may be limited, however, as small peripherally located intraductal masses or masses without an associated dilated duct may not be identified. Therefore, galactography, MR imaging, and/or major duct excision may still be necessary in the symptomatic patient with a negative US examination.

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Finally, in the pregnant or lactating patient who presents with a palpable breast mass, focal breast pain, or bloody nipple discharge, US is also the initial imaging modality of choice. Targeted US examination in these patients can be used to identify most benign and malignant masses, including fibroadenomas, galactocoeles, lactating adenomas, abscesses, and invasive carcinomas. In a recent study by Robbins et al (69), a negative predictive value of 100% was found among 122 lesions evaluated with US in lactating, pregnant, or postpartum women. This is much higher than the pregnancy-associated breast cancer sensitivity of mammography, which has been reported in the range of 78%–87% (70,71). The diminished sensitivity of mammography is likely due to increased parenchymal density seen in these patients. However, since lactating breast parenchyma is more echogenic than most breast masses, hypoechoic breast cancers are more readily detected at US in pregnant patients.

 

 

Supplemental Screening Breast US

Because of the known limitations of mammography, particularly in women with dense breast tissue, supplemental screening with whole-breast US, in addition to mammography, is increasingly gaining widespread acceptance. Numerous independent studies have demonstrated that the addition of a single screening or whole-breast US examination in women with dense breast tissue at mammography will yield an additional 2.3–4.6 mammographically occult cancers per 1000 women (7280). Mammographically occult cancers detected on US images are generally small node-negative invasive cancers (Fig 12) (81). However, few studies have investigated the performance of incident screening breast US, and the optimal screening US interval is unknown. Berg and colleagues (82) recently demonstrated that incident annual supplemental screening US in intermediate- and high-risk women with mammographically dense breast tissue enabled detection of an additional 3.7 cancers per 1000 women screened.

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Handheld screening breast US is highly operator-dependent and the majority of screening breast US studies have relied on physician-performed examinations. As per the ACRIN 6666 protocol, a normal screening US examination should consist of a minimum of one image in each quadrant and one behind the nipple (83). Two studies have also demonstrated that technologist-performed handheld screening breast US can achieve similar cancer detection rates (76,78).

Automated whole-breast US is a recently developed alternative to traditional handheld screening breast US, in which standardized, uniform image sets may be readily obtained by a nonradiologist. Automated whole-breast US systems may utilize a standard US unit and a linear-array transducer attached to a computer-guided mechanical arm or a dedicated screening US unit with a 15-cm wide transducer (84,85). With these systems, over 3000 overlapping sagittal, transverse, and coronal images are obtained and available for later review by the radiologist, with associated 3D reconstruction. The advantages include less operator dependence, increased radiologist efficiency, and increased reproducibility, which could aid in follow-up of lesions.

A multi-institutional study has shown that supplemental automated whole-breast US can depict an additional 3.6 cancer per 1000 women screened, similar to physician-performed handheld screening US (85). However, disadvantages include the limited ability to scan the entire breast, particularly posterior regions in large breasts, time-consuming review of a large number of images by the radiologist, and the need to recall patients for a second US examination to re-evaluate indeterminate findings. Moreover, few investigators have compared the use of handheld with automated breast US screening. A single small recent study by Chang et al (86) demonstrated that of 14 cancers initially detected at handheld screening, only 57%–79% were also detected by three separate readers on automated whole-breast US images, with the two cancers missed by all three readers at automated whole-breast US, each less than 1 cm in size.

The use of supplemental screening breast US, performed in addition to mammography, remains controversial despite proof of the ability to detect small mammographically occult cancers. US has limited value for the detection of small clustered microcalcifications without an associated mass lesion. Low positive predictive values of biopsies performed of less than 12% have been consistently reported (77,87). No outcome study has been able to demonstrate a direct decrease in patient mortality due to the detection of these additional small and mammographically occult cancers. This would require a long, randomized screening trial, which is not feasible. Rationally, however, the early detection and treatment of additional small breast cancers should improve outcomes and reduce overall morbidity and mortality. Many insurance companies will not reimburse for screening breast US and historically, this examination has not been widely accepted in the United States.

Nevertheless, because of both the known efficacy of supplemental screening breast US and overall increased breast cancer awareness, more patients and clinicians are requesting this examination. In fact, some states now mandate that radiologists inform women of their breast density and advise them to discuss supplemental screening with their doctors. Although supplemental screening breast MR imaging is usually preferred for women who are at very high risk for breast cancer (ie, women with a lifetime risk of over 20%, for example those women who are BRCA positive or have multiple first-degree relatives with a history of premenopausal breast cancer), screening breast US should be considered in women at very high risk for breast cancer who cannot tolerate breast MR imaging, as well as those women with dense breast tissue and intermediate risk (ie, lifetime risk of 15%–20%, for example those women whose only risk factor is a personal history of breast cancer or previous biopsy of a high-risk lesion), or even average risk. Future studies are needed to establish strategies to reduce false-positive results and continue to optimize both technologist-performed handheld screening US and automated whole-breast US in women with mammographically dense breast tissue.

 

 Use of US for MR Imaging–depicted Abnormalities

MR imaging of the breast is now an integral part of breast imaging, most commonly performed to screen high-risk women and to further assess the stage in patients with newly diagnosed breast cancers. While MR has a higher sensitivity than mammography for detecting breast cancer, the specificity is relatively low (88). Lesions detected on MR images are often mammographically occult, but many can be detected with targeted US (Fig 13). Besides further US characterization of an MR imaging–detected lesion, US may be used to guide intervention for lesions initially detected at MR imaging. US-guided biopsies are considerably less expensive, less time consuming, and more comfortable for the patient than MR imaging–guided biopsies.

Picture13a

Picture13b

Some suspicious lesions detected at MR imaging will represent invasive ductal or lobular cancers, but many may prove to be intraductal disease, which can be challenging to detect at US. Meticulous scanning technique is required for an MR imaging–directed US examination, with knowledge of subtle sonographic signs and close correlation with the MR imaging findings and location. Precontrast T1 images are helpful to facilitate localization of lesions in relation to fibroglandular tissue (89). Because MR imaging abnormalities tend to be vascular, increased vascularity may also assist in detection of a subtle sonographic correlate (90). Having the MR images available for simultaneous review while performing the US examination will ideally permit such associative correlation. At the authors’ facility, computer monitors displaying images from the picture archiving and communication system are available in all US rooms for this purpose.

Recent studies have shown that 46%–71% of lesions at MR imaging can be detected with focused US (9094). Enhancing masses detected on MR images are identified on focused US images in 58%–65% of cases compared with nonmass enhancement, which is identified on focused US images in only 12%–32% of cases (9092). Some studies have shown that US depiction of an MR imaging correlate was independent of size (91,93,95). However, Meissnitzer et al (92) showed that size dependence is also important: For masses 5 mm or smaller, only 50% were seen, versus 56% for masses 6–10 mm, 73% for masses 11–15 mm, and 86% for masses larger than 15 mm. Likewise, this study also demonstrated that for nonmass lesions, a US correlate was found for 13% of those measuring 6–10 mm, 25% of those 11–15 mm, and 42% of those larger than 15 mm (92). In addition, many of these studies determined that when a sonographic correlate was discovered, the probability of malignancy was increased (9092). Since typical US malignant features such as spiculation and posterior shadowing may be absent and the pretest probability is higher for MR imaging–detected lesions, a lower threshold for biopsy should be considered when performing MR imaging–directed US compared with routine targeted US (90) or screening US.

Because lesions are often very subtle at MR-directed US examination and because of differences in patient positioning during the two examinations, careful imaging–histologic correlation is required when performing US-guided biopsy of MR imaging–detected abnormalities. For lesions sampled with a vacuum-assisted device and US guidance, Sakamoto et al (96) found a higher rate of false-negative biopsy results for MR imaging–detected lesions than for US-detected lesions, suggesting that precise US-MR imaging correlation may not have occurred. Meissnitzer et al (92) showed that although 91% of MR imaging–detected lesions had an accurate US correlate, 9% were found to be inaccurate. With ever-improving techniques and experience in breast US, the US visualization of MR imaging–detected abnormalities will likely continue to improve. Nevertheless, if a suspicious lesion is not identified sonographically, MR imaging–guided biopsy should still be performed, because the malignancy rate of sonographically occult MR imaging–detected lesions has been shown to range from 14% to 22% (91,95).

 

 

Preoperative Staging of Cancer with US

Breast MR imaging has been shown to be more sensitive than US in the detection of additional foci of mammographically occult disease in women with newly diagnosed breast cancer (9799). Nevertheless, when a highly suspicious mass is identified at mammography and US, immediate US evaluation of the remainder of the ipsilateral breast, the contralateral breast, and the axilla should be considered. If additional lesions are identified, preoperative staging with MR imaging can be avoided and US-guided biopsy can be promptly performed, saving the patient valuable time and expense (100). In a study by Moon et al (101), of 201 patients with newly diagnosed breast cancer, staging US demonstrated mammographically occult multifocal or multicentric disease in 28 patients (14%) and contralateral breast cancers in eight patients (4%), resulting in a change in therapy in 32 patients (16%).

US can also be used to identify abnormal axillary, supraclavicular, and internal mammary lymph nodes. Abnormal lymph nodes characteristically demonstrate focal or diffuse cortical thickening (≥3 mm in thickness), a round (rather than oval or reniform) shape, loss of the echogenic fatty hilum and/or nonhilar, disorganized, irregular blood vessels (102,103) (Fig 14). A positive US-guided CNB or fine-needle aspiration of a clinically abnormal axillary lymph node in a patient with a known breast cancer can aid patient management, by avoiding the need for sentinel node biopsy and allowing the patient instead to proceed directly to axillary lymph node dissection or neoadjuvant chemotherapy.

Picture14

 

 Interventional Breast US

US-guided interventional procedures have increased in volume in recent years and US is now the primary biopsy guidance technique used in many breast imaging centers. Most palpable lesions, as well as lesions detected at mammography, MR imaging, or screening US, can be sampled with US. With current high-resolution transducers, even suspicious intraductal microcalcifications may be detected and sampled.

While US-guided procedures require technical skills that must be developed and can be challenging, once mastered this technique allows precise real-time sampling of the lesion, which is not possible with either stereotactic or MR imaging–guided procedures. US-guided procedures do not require ionizing radiation or intravenous contrast material. US procedures are more tolerable for patients than stereotactic (104) or MR imaging–guided procedures because US-guided procedures are faster and more comfortable, as breast compression and uncomfortable biopsy coils or tables are not necessary and the procedure may be performed with the patient supine (104106).

Most literature has shown that automated 14-gauge CNB devices are adequate for the majority of US-guided biopsies (107115). Image-guided CNB is preferable to fine-needle aspiration cytology of breast masses because of superior sensitivity, specificity, and diagnostic accuracy (116). DCIS, malignant invasion, and hormone receptor status of invasive breast cancers can be determined with CNB samples, but not with fine-needle aspiration cytology. Fine-needle aspiration may be performed, however, in complicated cysts and symptomatic simple cysts. In these cases, the cyst aspirate fluid can often be discarded; cytology is usually only necessary if the fluid is frankly bloody (117).

The choice of performing fine-needle aspiration or CNB of a suspicious axillary lymph node depends on radiologist preference and the availability of an experienced cytopathologist, although CNB is usually more accurate than fine-needle aspiration biopsy (118,119). Fine-needle aspiration may be preferred for suspicious deep lymph nodes in proximity to the axillary vessels, whereas CNB may be preferred in large nodes with thickened cortices, particularly if determination of hormone receptor status or immunohistochemistry is desired, since more tissue is required for these assays. If lymphoma is suspected, a core should be placed in saline and also in conventional formalin.

While the underestimation rate of malignancy can be considerable for high-risk lesions such as atypical hyperplasia, such histology is not commonly found in lesions undergoing US-guided CNB. Multiple studies have shown a false-negative rate for US CNB biopsy of around 2%–3% (107115). Although the contiguous and larger samples obtained with a vacuum-assisted biopsy device undoubtedly reduce sampling error, the vacuum-assisted biopsy is a more expensive and more invasive procedure (109). In the authors’ experience, vacuum-assisted US biopsy is to be considered for small masses, intraductal or intracystic lesions, or lesions with subtle microcalcifications. These may be difficult to adequately sample with a spring-loaded automatic firing device. Alternatively, for more accurate sampling of such challenging cases, as well as some axillary lymph nodes and masses smaller than 1 cm in size, automated CNB needles designed to place the inner trough of the needle within a lesion before firing can be utilized (Fig 15). With this technique, the sampling trough of the CNB needle can be clearly visualized within the lesion before the overlying outer sheath is fired. Regardless of needle choice, a postbiopsy clip marker should be placed followed by a postbiopsy mammogram to document clip position. This will assist with follow-up imaging, facilitating mammography and/or MR imaging correlation.

Picture15a

 

Picture15b

There has been recent interest in the percutaneous removal of benign breast lesions by using US-guided vacuum-assisted biopsy. While in general, proved benign concordant lesions can safely remain in the breast, some patients desire removal. Percutaneous US-guided removal with a vacuum-assisted biopsy device can replace surgical removal in some cases, particularly for small lesions (1 cm in size or less). Several reports have shown promising results demonstrating rates of complete lesion excision, varying from 61% to 94% (120124). Dennis et al (125) demonstrated that vacuum-assisted US-guided biopsy could be used to excise intraductal lesions resulting in resolution of problematic nipple discharge in 97% of patients. Even on long-term follow-up, most studies show low rates of residual masses, more commonly observed in larger fibroadenomas.

 

 Intraoperative Breast US

The use of two-dimensional and 3D intraoperative US may decrease the incidence of positive margins and decrease re-excision rates (126130) particularly in the setting of lumpectomy for palpable cancers, when US is used to assess the adequacy of surgical margins to determine the need for additional tissue removal. Similarly, intraoperative US has also been utilized to improve detection and removal of metastatic lymph nodes during sentinel lymph node assessment (131).

 

Future Directions

Intravenous US microbubble contrast agents have been used to enhance US diagnosis by means of analysis, enhancement patterns, the rates of uptake and washout, and identification of tumor angiogenesis. In addition, preliminary research has shown that intravenous US contrast agents may be able to depict tissue function with the potential to deliver targeted gene therapy to selected tumor cells (132). However, there are currently no intravenous US contrast agents approved for use in breast imaging by the U.S. Food and Drug Administration. Other potential advances in breast US include fusion imaging, which involves the direct overlay of correlative MR imaging with targeted US. Another evolving area is that of US computer-aided detection, which may be of particular benefit when combined with automated whole-breast screening US.

 

 Summary

Technical advances in US now allow comprehensive US diagnosis, management, and treatment of breast lesions. Optimal use of US technology, meticulous scanning technique with careful attention to lesion morphology, and recognition and synthesis of findings from multiple imaging modalities are essential for optimal patient management. In the future, as radiologists utilize US for an ever-increasing scope of indications, become aware of the more subtle sonographic findings of breast cancer, and apply newly developing tools, the value of breast US will likely continue to increase and evolve.

 

Essentials

  • • Breast US is operator dependent; knowledge and understanding of the various technical options currently available are important for image optimization and accurate diagnosis.
  • • US is an interactive, dynamic modality and real-time scanning is necessary to assess subtle findings associated with malignancy.
  • • Ability to synthesize the information obtained from the breast US examination with concurrent mammography, MR imaging, and clinical breast examination is necessary for accurate diagnosis.
  • • The use of screening breast US in addition to mammography, particularly in women with dense breast tissue, is becoming more widely accepted in the United States.
  • • Breast US guidance is the primary biopsy method used in most breast imaging practices, and the radiologist should be familiar with various biopsy devices and techniques to adequately sample any breast mass identified at US.

 

Disclosures of Conflicts of Interest: R.J.H. No relevant conflicts of interest to disclose. L.M.S. Financial activities related to the present article: none to disclose. Financial activities not related to the present article: educational consultant in vascular US to Philips Healthcare; payment for lectures on breast US from Educational Symposia; payment for development of educational presentations from Philips Healthcare. Other relationships: none to disclose. L.E.P. Financial activities related to the present article: none to disclose. Financial activities not related to the present article: consultant to Hologic. Other relationships: none to disclose.

Abbreviations:

BI-RADS = Breast Imaging and Reporting Data System

CNB = core needle biopsy

DCIS = ductal carcinoma in situ

3D = three dimensional

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    . Multifocal, multicentric, and contralateral breast cancers: bilateral whole-breast US in the preoperative evaluation of patients.Radiology 2002;224(2):569–576.

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    1. Philpotts LE

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Following (or not) the guidelines for use of imaging in management of prostate cancer.

Writer and curator: Dror Nir, PhD

Over diagnosis and over treatment is a trend of the last two decades. It leads to increase in health-care costs and human-misery.

The following headline on Medscape; Swedes Show That We Can Improve Imaging in Prostate Cancer elicited my curiosity.

I was expecting “good news” – well, not this time!

In spite the “general language” the study that the above mentioned headline refers to is not addressing the global use of imaging in prostate cancer patients’ pathway but is specific to use of radionuclide bone-scans as part of patients’ staging.  The “bad-news” are that realization that the Swedish government had to invest many man-years to achieve “success” in reducing unnecessary use of such imaging in low risk patients. Moreover, the paper reveals under-use of such imaging technology for staging high risk prostate cancer patients.

Based on this paper, one could come to the conclusion that in reality, we are facing long lasting non-conformity with established guidelines related to the use of “full-body” imaging as part of the prostate cancer patients’ pathway in Europe and USA.

Here is a link to the original paper:

Prostate Cancer Imaging Trends After a Nationwide Effort to Discourage Inappropriate Prostate Cancer Imaging, Danil V. MakarovStacy LoebDavid UlmertLinda DrevinMats Lambe and Pär Stattin Correspondence to: Pär Stattin, MD, PhD, Department of Surgery and Perioperative Sciences, Urology and Andrology, Umeå University, SE- 901 87 Umeå, Sweden (e-mail:par.stattin@urologi.umu.se).

JNCI J Natl Cancer Inst (2013)doi: 10.1093/jnci/djt175

 

For convenience, here are the highlights:

  • Reducing inappropriate use of imaging to stage incident prostate cancer is a challenging problem highlighted recently as a Physician Quality Reporting System quality measure and by the American Society of Clinical Oncology and the American Urological Association in the Choosing Wisely campaign.

 

  • Since 2000, the National Prostate Cancer Register (NPCR) of Sweden has led an effort to decrease national rates of inappropriate prostate cancer imaging by disseminating utilization data along with the latest imaging guidelines to urologists in Sweden.

  • Results Thirty-six percent of men underwent imaging within 6 months of prostate cancer diagnosis. Overall, imaging use decreased over time, particularly in the low-risk category, among whom the imaging rate decreased from 45% to 3% (P < .001), but also in the high-risk category, among whom the rate decreased from 63% to 47% (P < .001). Despite substantial regional variation, all regions experienced clinically and statistically (P < .001) significant decreases in prostate cancer imaging.

 

t1

t2

fig1

fig2

  • These results may inform current efforts to promote guideline-concordant imaging in the United States and internationally.

  • In 1998, the baseline low-risk prostate cancer imaging rate in Sweden was 45%. Per the NCCN guidelines (7), none of these men should have received bone imaging unless they presented with symptoms suggestive of bone pain (8,24). In the United States, the imaging rate among men with low-risk prostate cancer has been reported to be 19% to 74% in a community cohort and 10% to 48% in a Surveillance Epidemiology and End Results (SEER)–Medicare cohort (10–13,16). It is challenging to compare these rates directly across the two countries because the NPCR aggregates all staging imaging into one variable. However, our sampling revealed that 88% of those undergoing imaging had at least a bone scan, whereas only 11% had any CTs and 10% had any MRI. This suggests that baseline rates of bone scan among low-risk men in Sweden were similar to those among their low-risk counterparts in the United States, whereas rates of axial imaging were likely much lower. During the study period, rates of prostate cancer imaging among low-risk men in Sweden decreased to 3%, substantially lower than those reported in the United States at any time.

  • Miller et al. describe a decline in imaging associated with a small-scale intervention administered in three urology practices located in the United States participating in a quality-improvement consortium. Our study’s contribution is to demonstrate that a similar strategy can be applied effectively at a national scale with an associated decline in inappropriate imaging rates, a finding of great interest for policy makers in the United States seeking to improve health-care quality.

  • In 1998, the baseline high-risk prostate cancer imaging rates in Sweden were 63%, and decreased by 43% in 2008 (rising slightly to 47% in 2009). Based on our risk category definitions and the guidelines advocated in Sweden, all of these men should have undergone an imaging evaluation (8,24). Swedish rates of prostate cancer imaging among men with high-risk disease are considerably lower than those reported from the SEER–Medicare cohort, where 70% to 75% underwent bone scan and 57% to 58% underwent CT (13,16). These already low rates of imaging among men with high-risk prostate cancer only decreased further during the NPCR’s effort to promote guideline-concordant imaging. Clearly in both countries, imaging for high-risk prostate cancer remains underused despite the general overuse of imaging and numerous guidelines encouraging its appropriate use (3–9).

Similar items I have covered on this this Open Access Online Scientific Journal:

Not applying evidence-based medicine drives up the costs of screening for breast-cancer in the USA.

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Ultrasound in Radiology – Results of a European Survey

Reporter and Curator; Dror Nir, PhD

Ultrasound is by far, the most frequently used imaging modality in patient’s pathway being used by office-based clinicians and in most of hospitals’ departments. This is also true for cancer patients. As the contribution of imaging to the clinical assessment of patients becomes more substantial, the argument around “who is qualified” to perform such assessment is becoming louder and definitely more relevant!

Both the European and the North America Radiology societies are pushing towards establishment of centralized ultrasound services within the hospitals radiology department, still most ultrasound machines are spread between the different departments and being used by all practitioners. ESR’s working group on ultrasound published a report on the status of ultrasound-practice in European hospitals. Quite a shame; only 13% of the hospital addressed for participation in the survey reacted positively. I would like to highlight the most relevant conclusion from this survey, which is valid no matter which hand is holding the probe: Technique-oriented teaching, time and examinations are necessary to learn how to use Ultrasound properly within the framework of organ-oriented and disease training. Personally, I would support the idea that when it comes to management of cancer patients, this will become a “quality requirement” by law, similar to rules applicable to using radio-active substances.

 Here below is the full report:

Organisation and practice of radiological ultrasound in Europe: a survey by the ESR Working Group on Ultrasound

European Society of Radiology (ESR) 

Neutorgasse 9/2, AT-1010 Vienna, Austria

European Society of Radiology (ESR)

Email: communications@myesr.org

URL: http://www.myESR.org

Received: 25 April 2013Accepted: 26 April 2013Published online: 29 May 2013

Abstract

Objectives

To gather information from radiological departments in Europe assessing the organisation and practice of radiological ultrasound and the diagnostic practice and training in ultrasound.

Methods

A survey containing 38 questions and divided into four groups was developed and made available online. The questionnaire was sent to over 1,000 heads of radiology departments in Europe.

Results

Of the 1,038 radiologists asked to participate in this survey, 123 responded. Excluding the 125 invitations to the survey that could not be delivered, the response rate was 13 %.

Conclusion

Although there was a low response rate, the results of this survey show that ultrasound still plays a major role in radiology departments in Europe: most departments have the technical capabilities to provide patients with up-to-date ultrasound examinations. Although having a centralised ultrasound laboratory seems to be the way forward, most ultrasound machines are spread between different departments. Ninety-one per cent of answers came from teaching hospitals reporting that training is regarded as an art and is needed in order to learn the basics of scanning techniques, after which working in an organ-oriented manner is the best way to learn how to integrate diagnostic US within the clinical context and with all other imaging techniques.

Main Messages

• Hospitals should introduce centralised ultrasound laboratories to allow for different competencies in US under the same roof, share human and technological resources and reduce the amount of equipment needed within the hospital.

• Technique-oriented teaching, time and examinations are necessary to learn how to use US properly within the framework of organ-oriented training.

• A time period of about 6 months dedicated solely to learning US scanning techniques is deemed sufficient in most cases.

INTRODUCTION

The Working Group on ultrasound (US) of the European Society of Radiology was founded in 2009 with the aim of supporting increased quality and visibility of US within radiological departments as well as strengthening the position of US within the radiology community.

Among the many practical goals assigned to the group, one of the most important has been to gather information about the organisation and practice of radiological US in Europe.

This article reports the results of a survey assessing how diagnostic US is practiced and how training in US is organised in radiological departments of European hospitals. Questions were also aimed at evaluating the practice of US within both radiology and other hospital departments in order to understand the relationships among the different users of this technique. A comparison with the results of a previous survey on the US activities within 17 academic radiological departments throughout Europe published in 1999 by Schnyder et al. [1] was also attempted.

MATERIALS AND METHODS

A questionnaire was developed to obtain data about the practice of diagnostic US within radiology departments in Europe.

The survey contained 38 questions that were divided into four groups:

(1)

Related to the hospital: location; dimensions; presence or absence of teaching duties.

(2)

Related to the workload of US: number of US examinations/year, amount of US equipment available; state of available technology; types of most frequent examinations; organisation of the US laboratory; presence of sonographers; methods of reporting and archiving US examinations.

(3)

Related to the teaching of US to radiology residents: organisation and duration of training programmes; number of examinations to be performed before completion of the training period; presence of training programmes dedicated to sonographers or other non-radiology residents.

(4)

Related to the US examinations performed outside radiology in each hospital; clinical specialists most often involved in performing directly US; availability of special techniques, such as contrast-enhanced ultrasound (CEUS); methods of reporting and archiving US examinations.

The questionnaire was made available online and an invitation to fill it in was sent to all 1,038 heads of radiology departments throughout Europe within the database of the European Society of Radiology. The invitation was repeated three times over a period of 3 months, between June and August 2011.

RESULTS

There were 123 responses to the questionnaire. Considering that 125/1,038 e-mail messages were reported as “undelivered”, the response rate to the invitation was 13 %. Many responders did not answer all the questions presented in the questionnaire, and some answers and comments were somewhat difficult to understand and evaluate.

First group of questions

Answers were gathered from different parts of Europe; 63.4 % were from five nations (Germany, Austria, France, Spain and Italy). The distribution according to countries is presented in Table 1.

Table 1

Nationality of responders

Germany (DE)

19

Austria (AT)

18

France (FR)

16

Spain (ES)

14

Italy (IT)

11

Hungary (HU)

7

Switzerland (CH)

5

The Netherlands (NL)

4

Turkey (TR)

3

UUK

3

Czech Rep (CZ)

3

Poland (PL)

2

Denmark (DK)

2

Romania (RO)

2

Norway (NO)

2

Croatia (HR)

2

Portugal (PT)

2

Belgium (BE)

2

Greece (GR)

1

Montenegro (ME)

1

Lithuania (LT)

1

Ireland (IE)

1

Serbia (RS)

1

Sweden (SE)

1

There were 25 responses (20.3 %) from hospitals with fewer than 400 beds, 52 (42.3 %) from hospitals with between 400 and 1,000 beds and 46 (37.4 %) from hospitals with more than 1,000 beds. Most answers were from teaching hospitals (91.1 %).

Second group of questions

Most radiology departments (77 %) have fewer than 10 working US units; 22 % have between 10 and 20 US machines; only 0.8 % have more than 20 machines. Small, portable units are available in 64.5 % of departments, 3D/4D capabilities are present in 52 % and elastography in 48.2 %, and 67.3 % have the possibility to perform CEUS examinations.

Up to 57.6 % of radiology departments perform more than 10,000 examinations per year; between 3,000 and 10,000 examinations per year are performed in 33.1 % of cases; only 9.3 % of departments perform fewer than 3,000 examinations.

Abdominal US is the most frequent exam (51.51 %), followed by breast (14.46 %), musculoskeletal (11.59 %), pelvic (10.88 %) and vascular (10.42 %) US examinations. Contrast-enhanced US (CEUS) studies constitute about 4.39 %. US is used by radiologists in emergency in 96.6 % of cases and in paediatrics in 74.6 %. Comments indicate that most of those who answered “no” did not have a paediatric section in their hospital.

Transvaginal US is used in obstetric examinations by 15.8 % of responders and in gynaecological studies by 50.7 %. Endoscopic US is used by radiologists in 13.4 % and intravascular US in 14.6 %; radiologists are called by surgeons for intraoperative US in 64.2 % of cases.

There were 49 responders who indicated the actual number of US examinations performed/year. The characteristics of hospitals in which the radiology department performs more than 20,000 ultrasound examinations/year are presented in Table 2.

Table 2

Characteristics of the hospitals in which the radiology department performs more than 20,000 US examinations/year (nationality, presence/absence of teaching duties, number of inpatients, number of US machines available, ratio between number of US examinations performed by non-radiology specialists vs. radiologists)

t2

Those who reported fewer than 5,000 US examinations/year are reported in Table 3.

Table 3

Characteristics of the hospitals in which the radiology department performs less than 5,000 US examinations/year (nationality, presence/absence of teaching duties, number of inpatients, number of US machines available, ratio between number of US examinations performed by non-radiology specialists vs. radiologists)

t3

Third group of questions

The first question in this group was whether the hospital was organised with a centralised US laboratory where physicians from all specialties work together.

There were 13/110 positive answers (11.8 %) from Germany (5), Spain (3), Austria (2), Hungary (2) and Croatia (1). All other hospitals have US machines scattered throughout the different radiological and non-radiological departments. The centralised US laboratory is organised together by the radiology and the internal medicine departments in three cases; it is truly multidisciplinary, with all specialties concurring, in three others; it is run by radiology in two. The remaining two positive answers did not provide further detail about their organisation.

The second question related to the role of sonographers. Only 15/110 (13.6 %) department heads stated they work with sonographers. They are located in Spain (3), Germany (2), UK (2), The Netherlands (2), Austria (1), Belgium (1), Ireland (1), Lithuania (1) and Montenegro (1). In all others, US examinations are done directly by the radiologists. There were 12 comments describing how the work of sonographers is organised. Sonographers do both the examination and the report, with the radiologist checking difficult cases only in four hospitals; sonographers do the studies and the radiologist takes a final look and writes the reports in six; two departments state they use sonographers for vascular examinations only.

The third question related to the organisation of training programmes in US. Radiology residents are trained in 91.1 % of responders. Some centres organise a theoretical course on basic principles of US before starting practical activity. Then, clinical practice is usually performed according to organ/systems training schemes. Residents work under close supervision of a senior radiologist: they approach the patient, perform a preliminary examination and issue a first report, which is then checked by the expert. The aim is to obtain progressive growth of competences: from scanning capabilities, to reporting capabilities, to complete independence.

The length of the period of training within the US laboratory in the various teaching hospitals and the minimum number of US examinations required before the end of the residency period are summarised in Tables 4 and5.

Table 4

Length of the period of training within the US laboratory in the 84 teaching hospitals that reported it

No. of teaching hospitals

Length of training

13

<4 months

38

4–6 months

26

6–12 months

7

>1 year

Table 5

Minimum number of US examinations to be performed before the end of the residency period in the 75 teaching hospitals that reported it

No. of teaching hospitals

Minimum no. of US examination

20

<500

16

500–1,000

17

1,000–2,000

22

>2,000

There was a direct correlation between the number of US exams performed in the department and the depth of US involvement during training: training programmes in the two hospitals where the lowest number of US examinations/year is performed indicate a period of 3 months and 250 and 500 examinations. However, a hospital with a workload of 45,000 US studies per year (in which, however, the examinations are performed by sonographers) suggested only 2–3 months of training and 100 exams before the end of the residency period.

Training is also provided for non-radiology residents in 37 hospitals. It is most frequently offered to internal medicine, gastroenterology, surgery, anesthesiology, vascular surgery and paediatrics. Comments indicate that these radiology courses allow only theoretical teaching, since observation, but not direct contact with patient, is provided for non-radiologists.

All 15 departments working with sonographers provide, or are planning to provide, starting in 2012, training courses for these professionals. These include both theory and practice; the theoretical part is done, in some cases, together with radiology residents.

As an important technical point, it must be noted that US images performed by radiologists are recorded into PACS systems in 85.6 % of cases. Comments on this question indicated that not all equipment is linked to PACS and that only selected images or videos are often archived; furthermore, technical problems in archiving videos have been reported.

A final group of questions pertained to the US examinations performed outside the radiology department in each hospital.

One question asked about the proportion of US examinations performed by radiologists vs. those performed by non-radiologists. European radiologists, as a whole, still perform a higher number of examinations (61.27 %) than non-radiologists (38.32 %). Differences in the percentage of studies performed in the different hospitals are presented in Table 6.

Table 6

Proportion of US examinations performed by radiologists vs. non-radiologists. Although radiologists, as a whole, perform more US examinations than non-radiologists, the table shows there are differences among different departments, with slightly more than 50 % performing more than 70 % of the studies

% of hospital US exams performed by radiologists

No. of radiology departments

≥90 %

25 (20.32 %)

70–90 %

37 (30.08 %)

10–70 %

57 (46.35 %)

<10 %

4 (3.25 %)

Comments indicate that most OB/GYN, neurology, vascular, urology, internal medicine, anaesthesiology and gastroenterology departments run their own US units in their wards. CEUS is used in 35.1 % of gastroenterology departments, in 15.1 % of internal medicine, in 10.6 % of transplant units and in 10.4 % of nephrology departments.

The examinations performed out of the radiology department are formally reported in 64.4 % of cases only. Comments indicate that reports are fully stored within the Hospital Information System (HIS) in 31 cases; storage is only partial in 24; no HIS storage is used in 5 cases.

US images obtained outside of the radiology department are recorded into the PACS system of the hospital in 18.3 % of cases only.

DISCUSSION

Several considerations are raised from the results of this survey.

First, there was a low response rate to the survey itself. There were only 123 answers to the 913 received messages asking for information from radiology department heads (a mere 13 %). It is hoped that this low response rate relates to the many committments on their side and not to low interest in the role of US within radiology [23].

Second, most responders indicated that US is still an important part of the activities of the radiology department. Only 9.3 % report fewer than 3,000 examinations/year. It must be noted that there may be a bias in these figures, since it is conceivable that responders were more interested in US than those who did not answer the questionnaire (even if there were responders who indicated that, in their hospital, US is done mostly outside of the radiology department). Most of the workload is due to abdomino-pelvic exams, followed by breast, musculoskeletal and vascular applications. Furthermore, state-of-the-art equipment is used in about 50 % and CEUS can be performed in 64.2 %. Portable machines are available in 64.5 %, transvaginal US examinations of the pelvis are used in 50.7 %, and radiologists are still involved in intraoperative US examinations in 64.2 % of cases. Most departments still have the technical capabilities to provide up-to-date US answers to the requests they receive.

Another consideration relates to the organisation of US within the hospital. In most cases US machines are scattered throughout the different departments, and only 13 hospitals have organised a centralised US laboratory where all physicians from different specialities come to examine their patients. Although centralisation seems the best way to run a US service, there are several factors that can explain why this is not the case, many of which stem from tradition. US laboratories, in fact, commonly arose separately from one another, following the initiatives of the different specialists who started introducing this technique in their practice. Then, there is a disposition to maintain independence and separate departmental income from the activities as well as the desire to control all aspects of patients’ care.

Only 15 departments reported they are working with sonographers. Although it is known that in Europe most radiologists perform US examinations directly, it is believed that this figure underestimates the real contribution of these professionals. A possible explanation is that only three hospitals from the UK answered the questionnaire; in the UK sonographers play a major role in dealing with the US workload.

Most answers to the questionnaire came from teaching hospitals (91.1 %). Comments on how training is organised state that US scanning is commonly regarded as an art, taught from maestro to pupil, with progressive growth in scanning and reporting capabilities. In addition, most report that US is taught within an organ-/system-oriented training system. The “art” of US is highly dependent on the operator’s dedication and technical ability, and this has to be properly taught. Additionally, a period of training within a dedicated US laboratory is probably needed to learn the basics of scanning techniques. After learning the technique, working in an organ-oriented manner is surely the best way to learn how to integrate diagnostic US within the clinical context and with all other imaging techniques.

There were 13 teaching hospitals in which fewer than 4 months is deemed sufficient, and in 20 cases having fewer than 500 examinations before the end of the residency is regarded as complete training.

The low number of US examinations performed in some training centres can jeopardise teaching. The recruitment of patients for adequate training can be impossibile to obtain in low-volume practices, leading to a further decrease of radiological US for future generations of radiologists. Furthermore, the use of sonographers can make teaching the practical skills of US scanning difficult. In a hospital with high-volume US practice (45,000 cases/year) in which the examinations are performed by sonographers, residents are asked to remain in the US laboratory only for 2–3 months and to perform only 100 examinations before the end of training. When in clinical practice in a hospital without sonographers, these radiologists would not be able to carry out even routine diagnostic US examinations. On the contrary, the role of expert sonographers as a resource to provide practical training to radiology residents has not been considered and can be explored.

The results of this survey show a large heterogeneity in the use of US within radiology throughout Europe. There are hospitals in which the majority of US examinations are still performed by radiologists, and others in which radiologists are left with only a small proportions of studies.

Similar findings were observed by Schnyder et al. in 1999 [1]. From their survey in 17 academic radiology departments throughout Europe, these authors reported that in some nations radiologists had full control of US, while this was not the case in Germany, Austria and Switzerland. The situation seems somewhat worse today, since there are 22 hospitals (18.2 %) in different nations (Austria, Poland, Germany, France, UK, Norway, Switzerland and Italy) in which radiologists perform less than 70 % of all US examinations and 5 (4 %) who answered they do less than 10 % of the studies. Since the answers to the questionnaire were provided by radiology departments, the figures for radiological activity can be considered as precise. On the contrary, it is possible that those answers on the US activities out of radiology can be regarded as an estimate. However, to the best of our knowledge, the data in the survey of Schnyder et al. were also obtained in a similar way, and a comparison can thus be made.

The percent decrease in the number of US examinations done in radiology vs. those performed outside radiology is probably related to a marked increase of the use of US by non-radiology clinicians rather than to a decreased attention to this technique by radiologists. In fact, new specialists, such as emergency physicians and anesthesiologists, are now using this technique as a complement to their visit or as a guide to therapeutic manoeuvres, and the so-called “point-of-care US” philosophy, in which US equipment accompanies the physician at the patient’s bedside to guide his/her therapeutic decision making, is gaining popularity.

An additional point to be considered relates to the recording of US reports and images into the hospital informations system and PACS. US examinations performed by radiologists are archived within the PACS system in 85.6 %, while those performed by non-radiologists are stored in only 18.3 % of cases. Furthermore, radiologists provide a formal report in virtually all cases, while examinations performed out of radiology are formally reported in 64.4 %. Costs and technical difficulties in connecting all equipment to PACS and RIS are described as reasons for not recording US images, and this is especially the case for recording of video clips. The use of “point-of-care US” is a further difficulty for connecting equipment to PACS, and, within this framework, the US exam is not regarded as a separate study but as part of the physician visit. However, to have all US images and reports of the patient recorded and available for consultation could greatly help during subsequent studies, and efforts have to be made to develop consensus with clinical colleagues to increase connectivity and to report all US studies, at least as a description within the patients’ charts. Within the framework of the relationships established by the ESR WG in US with the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB), it has been agreed to prepare and publish a recommendation about the necessity, for all US examinations, of a formal report and proper archiving of both report and images.

ACTION POINTS

Two points of action can be suggested.

The first relates to the centralisation of the US laboratory. Although at the moment only a small number of hospitals are working according to this model, radiologists should take the lead in proposing such organisation [4]. This would allow the gathering of all the different competencies in US under the same roof, to share human and technological resources and to reduce the amount of equipment needed within the hospital. In an era of cost containments, a centralised US laboratory can allow each US scanner operate for longer hours and with higher numbers of examinations, resulting in an optimisation of resources. Furthermore, requests to upgrade and/or renovate equipment would possibly be easier if coming from a large laboratory and shared by different hospital departments. Another advantage would be having people with different backgrounds work in the same environment, thus promoting exchange and integration of their knowledge and possibly resulting in better patient care. It would be easier, in this respect, to prepare institutional guidelines and protocols that place US in the correct perspective towards all other imaging modalities and, most importantly, towards patients’ needs. It is not clear from the survey how this way of working is organised on a day-to-day basis, and especially how emergency services are provided (i.e. if all specialists concur in the emergency or if this is left to radiologists only), but an integrated management and organisational infrastructure bears numerous advantages for cost containment, quality standards and efficiency.

The second point of action relates to training in US within radiology residency programmes. In the opinion of the ESR Working Group on US, radiologists need to develop consensus on how many examinations under tutorship residents have to perform and on how much time they have to spend in ultrasound before the end of the training period. The results of the survey vary widely. However, out of 75 training centres that reported on the number of examinations, there were 39 (52 %) providing figures between 1,000 and 2,000 or higher. Therefore, approximately 2,000 seems to be a figure on which consensus can be reached. This figure also complies with what is suggested by the EFSUMB [5]. This federation provides recommendations about the number of examinations for training in the different subspeciality areas of US: the sum of studies for abdomen, breast, musculoskeletal and vascular training is 1,500, while figures for head and neck are not provided. The length of training is more complex to decide. A distinction has to be made here between the time needed to learn the technique of US scanning and the time needed to learn how to use US properly, to integrate it with other imaging techniques and to provide useful reports. In order to perform US, both approaches are needed. Technique-oriented teaching is necessary to learn how to perform the studies and to identify anatomy and pathology. Time and exams are needed to learn how to use US properly within the framework of organ-oriented training. A period of time of about 6 months dedicated solely to learning the US scanning technique can possibly be considered sufficient, as suggested by 76.2 % of responders. The capabilities of residents to perform US examinations have to be assessed during the training period, especially during and at the end of the technique-oriented part. It is known that the learning curve can vary widely among trainees, and longer times and higher numbers of examinations may be needed in some cases [6]. Additional time should be spent, and exams taken, during organ-oriented training. It must be underlined that organ-oriented teaching needs to include the proper role of US in each subspeciality and also take into account technical advances such as CEUS, 3D/4D and elastography and to use them when needed.

Acknowledgment

This article was kindly prepared by the ESR Working Group on US (M. Bachmann-Nielsen, M. Claudon, L. E. Derchi, S. Elliott, G. Mostbeck, C. Nicolau, S. Yarmenitis, A. Zubarev, Y. Menu–Chair of the ESR Professional Organisation Committee and J.A. Reekers–Chair of the ESR Subspecialty Societies Committee) on behalf of the European Society of Radiology. It was approved by the ESR Executive Council in April 2013.

Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.

References

1.

Schnyder P, Capasso P, Meuwly I-Y (1999) Turf battles in radiology: how to avoid/how to fight/how to win. Eur Radiol 9:741–748PubMedCrossRef

2.

Lockhart ME (2008) The role of radiology in the future of sonography. AJR 190:841–842PubMedCrossRef

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Derchi LE, Claudon M (2009) Ultrasound: a strategic issue for radiology? Eur Radiol 19:1–6PubMedCrossRef

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Krestin GP (2009) Maintaining identity in a changing environment: the professional and organizational future of radiology. Radiology 250:612–617PubMedCrossRef

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Minimum training recommendations for the practice of medical ultrasond in Europe. http://www.org/guidelines/guidelines01.asp

6.

Hertzberg BS, Kliewer MA, Bowie JD, Carroll BA, DeLong DH, Gray L, Nelson RC (2000) Physician training requirements in sonography: how many cases are needed for competence? AJR 174:1221–1227PubMedCrossRef

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Follow-up on Tomosynthesis

Writer & Curator: Dror Nir, PhD

Tomosynthesis, is a method for performing high-resolution limited-angle (i.e. not full 3600 rotation but more like ~500) tomography. The use of such systems in breast-cancer screening is steadily increasing following the clearance of such system by the FDA on 2011; see my posts – Improving Mammography-based imaging for better treatment planning and State of the art in oncologic imaging of breast.

Many radiologists expects that Tomosynthesis will eventually replace conventional mammography due to the fact that it increases the sensitivity of breast cancer detection. This claim is supported by new peer-reviewed publications. In addition, the patient’s experience during Tomosynthesis is less painful due to a lesser pressure that is applied to the breast and while presented with higher in-plane resolution and less imaging artifacts the mean glandular dose of digital breast Tomosynthesis is comparable to that of full field digital mammography. Because it is relatively new, Tomosynthesis is not available at every hospital. As well, the procedure is recognized for reimbursement by public-health schemes.

A good summary of radiologist opinion on Tomosynthesis can be found in the following video:

Recent studies’ results with digital Tomosynthesis are promising. In addition to increase in sensitivity for detection of small cancer lesions researchers claim that this new breast imaging technique will make breast cancers easier to see in dense breast tissue.  Here is a paper published on-line by the Lancet just a couple of months ago:

Integration of 3D digital mammography with tomosynthesis for population breast-cancer screening (STORM): a prospective comparison study

Stefano Ciatto†, Nehmat Houssami, Daniela Bernardi, Francesca Caumo, Marco Pellegrini, Silvia Brunelli, Paola Tuttobene, Paola Bricolo, Carmine Fantò, Marvi Valentini, Stefania Montemezzi, Petra Macaskill , Lancet Oncol. 2013 Jun;14(7):583-9. doi: 10.1016/S1470-2045(13)70134-7. Epub 2013 Apr 25.

Background Digital breast tomosynthesis with 3D images might overcome some of the limitations of conventional 2D mammography for detection of breast cancer. We investigated the effect of integrated 2D and 3D mammography in population breast-cancer screening.

Methods Screening with Tomosynthesis OR standard Mammography (STORM) was a prospective comparative study. We recruited asymptomatic women aged 48 years or older who attended population-based breast-cancer screening through the Trento and Verona screening services (Italy) from August, 2011, to June, 2012. We did screen-reading in two sequential phases—2D only and integrated 2D and 3D mammography—yielding paired data for each screen. Standard double-reading by breast radiologists determined whether to recall the participant based on positive mammography at either screen read. Outcomes were measured from final assessment or excision histology. Primary outcome measures were the number of detected cancers, the number of detected cancers per 1000 screens, the number and proportion of false positive recalls, and incremental cancer detection attributable to integrated 2D and 3D mammography. We compared paired binary data with McNemar’s test.

Findings 7292 women were screened (median age 58 years [IQR 54–63]). We detected 59 breast cancers (including 52 invasive cancers) in 57 women. Both 2D and integrated 2D and 3D screening detected 39 cancers. We detected 20 cancers with integrated 2D and 3D only versus none with 2D screening only (p<0.0001). Cancer detection rates were 5·3 cancers per 1000 screens (95% CI 3.8–7.3) for 2D only, and 8.1 cancers per 1000 screens (6.2–10.4) for integrated 2D and 3D screening. The incremental cancer detection rate attributable to integrated 2D and 3D mammography was 2.7 cancers per 1000 screens (1.7–4.2). 395 screens (5.5%; 95% CI 5.0–6.0) resulted in false positive recalls: 181 at both screen reads, and 141 with 2D only versus 73 with integrated 2D and 3D screening (p<0·0001). We estimated that conditional recall (positive integrated 2D and 3D mammography as a condition to recall) could have reduced false positive recalls by 17.2% (95% CI 13.6–21.3) without missing any of the cancers detected in the study population.

Interpretation Integrated 2D and 3D mammography improves breast-cancer detection and has the potential to reduce false positive recalls. Randomised controlled trials are needed to compare integrated 2D and 3D mammography with 2D mammography for breast cancer screening.

Funding National Breast Cancer Foundation, Australia; National Health and Medical Research Council, Australia; Hologic, USA; Technologic, Italy.

Introduction

Although controversial, mammography screening is the only population-level early detection strategy that has been shown to reduce breast-cancer mortality in randomised trials.1,2 Irrespective of which side of the mammography screening debate one supports,1–3 efforts should be made to investigate methods that enhance the quality of (and hence potential benefit from) mam­mography screening. A limitation of standard 2D mammography is the superimposition of breast tissue or parenchymal density, which can obscure cancers or make normal structures appear suspicious. This short coming reduces the sensitivity of mammography and increases false-positive screening. Digital breast tomosynthesis with 3D images might help to overcome these limitations. Several reviews4,5 have described the development of breast tomosynthesis technology, in which several low-dose radiographs are used to reconstruct a pseudo-3D image of the breast.4–6

Initial clinical studies of 3D mammography, 6–10 though based on small or selected series, suggest that addition of 3D to 2D mammography could improve cancer detection and reduce the number of false positives. However, previous assessments of breast tomosynthesis might have been constrained by selection biases that distorted the potential effect of 3D mammography; thus, screening trials of integrated 2D and 3D mammography are needed.6

We report the results of a large prospective study (Screening with Tomosynthesis OR standard Mammog­raphy [STORM]) of 3D digital mammography. We investi­gated the effect of screen-reading using both standard 2D and 3D imaging with tomosynthesis compared with screening with standard 2D digital mammography only for population breast-cancer screening.

  

Methods

Study design and participants

STORM is a prospective population-screening study that compares mammography screen-reading in two sequential phases (figure)—2D only versus integrated 2D and 3D mammography with tomosynthesis—yielding paired results for each screening examination. Women aged 48 years or older who attended population-based screening through the Trento and Verona screening services, Italy, from August, 2011, to June, 2012, were invited to be screened with integrated 2D and 3D mammography. Participants in routine screening mammography (once every 2 years) were asymptomatic women at standard (population) risk for breast cancer. The study was granted institutional ethics approval at each centre, and participants gave written informed consent. Women who opted not to participate in the study received standard 2D mammography. Digital mammography has been used in the Trento breast-screening programme since 2005, and in the Verona programme since 2007; each service monitors outcomes and quality indicators as dictated by European standards, and both have published data for screening performance.11,12

 

study design

Procedures

All participants had digital mammography using a Selenia Dimensions Unit with integrated 2D and 3D mammography done in the COMBO mode (Hologic, Bedford, MA, USA): this setting takes 2D and 3D images at the same screening examination with a single breast position and compression. Each 2D and 3D image consisted of a bilateral two-view (mediolateral oblique and craniocaudal) mammogram. Screening mammo­grams were interpreted sequentially by radiologists, first on the basis of standard 2D mammography alone, and then by the same radiologist (on the same day) on the basis of integrated 2D and 3D mammography (figure). Thus, integrated 2D and 3D mammography screening refers to non-independent screen reading based on joint interpretation of 2D and 3D images, and does not refer to analytical combinations. Radiologists had to record whether or not to recall the participant at each screen-reading phase before progressing to the next phase of the sequence. For each screen, data were also collected for breast density (at the 2D screen-read), and the side and quadrant for any recalled abnormality (at each screen-read). All eight radiologists were breast radiologists with a mean of 8 years (range 3–13 years) experience in mammography screening, and had received basic training in integrated 2D and 3D mammography. Several of the radiologists had also used 2D and 3D mammography for patients recalled after positive conventional mammography screening as part of previous studies of tomosynthesis.8,13

Mammograms were interpreted in two independent screen-reads done in parallel, as practiced in most population breast-screening programs in Europe. A screen was considered positive and the woman recalled for further investigations if either screen-reader recorded a positive result at either 2D or integrated 2D and 3D screening (figure). When previous screening mammograms were available, these were shown to the radiologist at the time of screen-reading, as is standard practice. For assessment of breast density, we used Breast Imaging Reporting and Data System (BI-RADS)14 classification, with participants allocated to one of two groups (1–2 [low density] or 3–4 [high density]). Disagreement between readers about breast density was resolved by assessment by a third reader.

Our primary outcomes were the number of cancers detected, the number of cancers detected per 1000 screens, the number and percentage of false posi­tive recalls, and the incremental cancer detection rate attributable to integrated 2D and 3D mammography screening. We compared the number of cancers that were detected only at 2D mammography screen-reading and those that were detected only at 2D and 3D mammography screen-reading; we also did this analysis for false positive recalls. To explore the potential effect of integrated 2D and 3D screening on false-positive recalls, we also estimated how many false-positive recalls would have resulted from using a hypothetical conditional false-positive recall approach; – i.e. positive integrated 2D and 3D mammography as a condition of recall (screening recalled at 2D mammography only would not be recalled). Pre-planned secondary analyses were comparison of outcome measures by age group and breast density.

Outcomes were assessed by excision histology for participants who had surgery, or the complete assessment outcome (including investigative imaging with or without histology from core needle biopsy) for all recalled participants. Because our study focuses on the difference in detection by the two screening methods, some cancers might have been missed by both 2D and integrated 2D and 3D mammography; this possibility could be assessed at future follow-up to identify interval cancers. However, this outcome is not assessed in the present study and does not affect estimates of our primary outcomes – i.e. comparative true or false positive detection for 2D-only versus integrated 2D and 3D mammography.

 

Statistical analysis

The sample size was chosen to provide 80% power to detect a difference of 20% in cancer detection, assuming a detection probability of 80% for integrated 2D and 3D screening mammography and 60% for 2D only screening, with a two-sided significance threshold of 5%. Based on the method of Lachenbruch15 for estimating sample size for studies that use McNemar’s test for paired binary data, a minimum of 40 cancers were needed. Because most screens in the participating centres were incident (repeat) screening (75%–80%), we used an underlying breast-cancer prevalence of 0·5% to estimate that roughly 7500–8000 screens would be needed to identify 40 cancers in the study population.

We calculated the Wilson CI for the false-positive recall ratio for integrated 2D and 3D screening with conditional recall compared with 2D only screening.16 All of the other analyses were done with SAS/STAT (version 9.2), using exact methods to compute 95 CIs and p-values.

Role of the funding source

The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding author (NH) had full access to all the data in the study and had final responsibility for the decision to submit for publication.

Results

7292 participants with a median age of 58 years (IQR 54–63, range 48–71) were screened between Aug 12, 2011, and June 29, 2012. Roughly 5% of invited women declined integrated 2D and 3D screening and received standard 2D mammography. We present data for 7294 screens because two participants had bilateral cancer (detected with different screen-reading techniques for one participant). We detected 59 breast cancers in 57 participants (52 invasive cancers and seven ductal carcinoma in-situ). Of the invasive cancers, most were invasive ductal (n=37); others were invasive special types (n=7), invasive lobular (n=4), and mixed invasive types (n=4).

Table 1 shows the characteristics of the cancers. Mean tumour size (for the invasive cancers with known exact size) was 13.7 mm (SD 5.8) for cancers detected with both 2D alone and integrated 2D and 3D screening (n=29), and 13.5 mm (SD 6.7) for cancers detected only with integrated 2D and 3D screening (n=13).

 

Table 1

Of the 59 cancers, 39 were detected at both 2D and integrated 2D and 3D screening (table 2). 20 cancers were detected with only integrated 2D and 3D screening compared with none detected with only 2D screening (p<0.0001; table 2). 395 screens were false positive (5.5%, 95% CI 5.0–6.0); 181 occurred at both screen-readings, and 141 occurred at 2D screening only compared with 73 at integrated 2D and 3D screening (p<0.0001; table 2). These differences were still significant in sensitivity analyses that excluded the two participants with bilateral cancer (data not shown).


Table 2

5.3 cancers per 1000 screens (95% CI 3.8–7.3; table 3) were detected with 2D mammography only versus 8.1 cancers per 1000 screens (95% CI 6.2–10.4) with integrated 2D and 3D mammography (p<0.0001). The incremental cancer detection rate attributable to inte­grated 2D and 3D screening was 2.7 cancers per 1000 screens (95% CI 1.7–4.2), which is 33.9% (95% CI 22.1–47.4) of the cancers detected in the study popu­lation. In a sensitivity analysis that excluded the two participants with bilateral cancer the estimated incre­mental cancer detection rate attributable to integrated 2D and 3D screening was 2.6 cancers per 1000 screens (95% CI 1.4–3.8). The stratified results show that integrated 2D and 3D mammography was associated with an incrementally increased cancer detection rate in both age-groups and density categories (tables 3–5). A minority (16.7%) of breasts were of high density (category 3–4) reducing the power of statistical comparisons in this subgroup (table 5). The incremental cancer detection rate was much the same in low density versus high density groups (2.8 per 1000 vs 2.5 per 1000; p=0.84; table 3).


Table 3

Table 4-5

Overall recall—any recall resulting in true or false positive screens—was 6.2% (95% CI 5.7–6.8), and the false-positive rate for the 7235 screens of participants who did not have breast cancer was 5.5% (5.0–6.0). Table 6 shows the contribution to false-positive recalls from 2D mammography only, integrated 2D and 3D mammography only, and both, and the estimated number of false positives if positive integrated 2D and 3D mammography was a condition for recall (positive 2D only not recalled). Overall, more of the false-positive rate was driven by 2D mammography only than by integrated 2D and 3D, although almost half of the false-positive rate was a result of false positives recalled at both screen-reading phases (table 6). The findings were much the same when stratified by age and breast density (table 6). Had a conditional recall rule been applied, we estimate that the false-positive rate would have been 3.5% (95% CI 3.1–4.0%; table 6) and could have potentially prevented 68 of the 395 false positives (a reduction of 17.2%; 95% CI 13.6–21.3). The ratio between the number of false positives with integrated 2D and 3D screening with conditional recall (n=254) versus 2D only screening (n=322) was 0.79 (95% CI 0.71–0.87).

Discussion

Our study showed that integrated 2D and 3D mam­mography screening significantly increases detection of breast cancer compared with conventional mammog­raphy screening. There was consistent evidence of an incremental improvement in detection from integrated 2D and 3D mammography across age-group and breast density strata, although the analysis by breast density was limited by low number of women with breasts of high density.

One should note that we investigated comparative cancer detection, and not absolute screening sensitivity. By integrating 2D and 3D mammography using the study screen-reading protocol, 1% of false-positive recalls resulted from 2D and 3D screen-reading only (table 6). However, significantly more false positives resulted from 2D only mammography compared with integrated 2D and 3D mammography, both overall and in the stratified analyses. Application of a conditional recall rule would have resulted in a false-positive rate of 3.5% instead of the actual false-positive rate of 5.5%. The estimated false positive recall ratio of 0.79 for integrated 2D and 3D screening with conditional recall compared with 2D only screening suggests that integrated 2D and 3D screening could reduce false recalls by roughly a fifth. Had such a condition been adopted, none of the cancers detected in the study would have been missed because no cancers were detected by 2D mammography only, although this result might be because our design allowed an independent read for 2D only mammography whereas the integrated 2D and 3D read was an interpretation of a combination of 2D and 3D imaging. We do not recommend that such a conditional recall rule be used in breast-cancer screening until our findings are replicated in other mammography screening studies—STORM involved double-reading by experienced breast radiologists, and our results might not apply to other screening settings. Using a test set of 130 mammograms, Wallis and colleagues7 report that adding tomosynthesis to 2D mammography increased the accuracy of inexperienced readers (but not of experienced readers), therefore having experienced radiologists in STORM could have underestimated the effect of integrated 2D and 3D screen-reading.

No other population screening trials of integrated 2D and 3D mammography have reported final results (panel); however, an interim analysis of the Oslo trial17 a large population screening study has shown that integrated 2D and 3D mammography substantially increases detection of breast cancer. The Oslo study investigators screened women with both 2D and 3D mammography, but randomised reading strategies (with vs without 3D mammograms) and adjusted for the different screen-readers,17whereas we used sequential screen-reading to keep the same reader for each exam­ination. Our estimates for comparative cancer detection and for cancer detection rates are consistent with those of the interim analysis of the Oslo study.17 The applied recall methods differed between the Oslo study (which used an arbitration meeting to decide recall) and the STORM study (we recalled based on a decision by either screen-reader), yet both studies show that 3D mammog­raphy reduces false-positive recalls when added to standard mammography.

An editorial in The Lancet18 might indeed signal the closing of a chapter of debate about the benefits and harms of screening. We hope that our work might be the beginning of a new chapter for mammography screening: our findings should encourage new assessments of screening using 2D and 3D mammography and should factor several issues related to our study. First, we compared standard 2D mammography with integrated 2D and 3D mammography the 3D mammograms were not interpreted independently of the 2D mammograms therefore 3D mammography only (without the 2D images) might not provide the same results. Our experience with breast tomosynthesis and a review6 of 3D mammography underscore the importance of 2D images in integrated 2D and 3D screen-reading. The 2D images form the basis of the radiologist’s ability to integrate the information from 3D images with that from 2D images. Second, although most screening in STORM was incident screening, the substantial increase in cancer detection rate with integrated 2D and 3D mammography results from the enhanced sensitivity of integrated 2D and 3D screening and is probably also a result of a prevalence effect (ie, the effect of a first screening round with integrated 2D and 3D mammography). We did not assess the effect of repeat (incident) screening with integrated 2D and 3D mammography on cancer detection it might provide a smaller effect on cancer detection rates than what we report. Third, STORM was not designed to measure biological differences between the cancers detected at integrated 2D and 3D screening compared with those detected at both screen-reading phases. Descriptive analyses suggest that, generally, breast cancers detected only at integrated 2D and 3D screening had similar features (eg, histology, pathological tumour size, node status) as those detected at both screen-reading phases. Thus, some of the cancers detected only at 2D and 3D screening might represent early detection (and would be expected to receive screening benefit) whereas some might represent over-detection and a harm from screening, as for conventional screening mam mography.1,19 The absence of consensus about over-diagnosis in breast-cancer screening should not detract from the importance of our study findings to applied screening research and to screening practice; however, our trial was not done to assess the extent to which integrated 2D and 3D mam­mography might contribute to over-diagnosis.

The average dose of glandular radiation from the many low-dose projections taken during a single acquisition of 3D mammography is roughly the same as that from 2D mammography.6,20–22 Using integrated 2D and 3D en­tails both a 2D and 3D acquisition in one breast com­pression, which roughly doubles the radiation dose to the breast. Therefore, integrated 2D and 3D mammography for population screening might only be justifiable if improved outcomes were not defined solely in terms of improved detection. For example, it would be valuable to show that the increased detection with integrated 2D and 3D screening leads to reduced interval cancer rates at follow-up. A limitation of our study might be that data for interval cancers were not available; however, because of the paired design we used, future evaluation of interval cancer rates from our study will only apply to breast cancers that were not identified using 2D only or integrated 2D and 3D screening. We know of two patients from our study who have developed interval cancers (follow-up range 8–16 months). We did not get this information from cancer registries and follow-up was very short, so these data should be interpreted very cautiously, especially because interval cancers would be expected to occur in the second year of the standard 2 year interval between screening rounds. Studies of interval cancer rates after integrated 2D and 3D mammography would need to be randomised controlled trials and have a very large sample size. Additionally, the development of reconstructed 2D images from a 3D mammogram23 provides a timely solution to concerns about radiation by providing both the 2D and 3D images from tomosynthesis, eliminating the need for two acquisitions.

We have shown that integrated 2D and 3D mammog­raphy in population breast-cancer screening increases detection of breast cancer and can reduce false-positive recalls depending on the recall strategy. Our results do not warrant an immediate change to breast-screening practice, instead, they show the urgent need for random­ised controlled trials of integrated 2D and 3D versus 2D mammography, and for further translational research in breast tomosynthesis. We envisage that future screening trials investigating this issue will include measures of breast cancer detection, and will be designed to assess interval cancer rates as a surrogate endpoint for screening efficacy.

Contributors

SC had the idea for and designed the study, and collected and interpreted data. NH advised on study concepts and methods, analysed and interpreted data, searched the published work, and wrote and revised the report. DB and FC were lead radiologists, recruited participants, collected data, and commented on the draft report. MP, SB, PT, PB, PT, CF, and MV did the screen-reading, collected data, and reviewed the draft report. SM collected data and reviewed the draft report. PM planned the statistical analysis, analysed and interpreted data, and wrote and revised the report.

Conflicts of interest

SC, DB, FC, MP, SB, PT, PB, CF, MV, and SM received assistance from Hologic (Hologic USA; Technologic Italy) in the form of tomosynthesis technology and technical support for the duration of the study, and travel support to attend collaborators’ meetings. NH receives research support from a National Breast Cancer Foundation (NBCF Australia) Practitioner Fellowship, and has received travel support from Hologic to attend a collaborators’ meeting. PM receives research support through Australia’s National Health and Medical Research Council programme grant 633003 to the Screening & Test Evaluation Program.

 

References

1       Independent UK Panel on Breast Cancer Screening. The benefits and harms of breast cancer screening: an independent review. Lancet 2012; 380: 1778–86.

2       Glasziou P, Houssami N. The evidence base for breast cancer screening. Prev Med 2011; 53: 100–102.

3       Autier P, Esserman LJ, Flowers CI, Houssami N. Breast cancer screening: the questions answered. Nat Rev Clin Oncol 2012; 9: 599–605.

4       Baker JA, Lo JY. Breast tomosynthesis: state-of-the-art and review of the literature. Acad Radiol 2011; 18: 1298–310.

5       Helvie MA. Digital mammography imaging: breast tomosynthesis and advanced applications. Radiol Clin North Am 2010; 48: 917–29.

6      Houssami N, Skaane P. Overview of the evidence on digital breast tomosynthesis in breast cancer detection. Breast 2013; 22: 101–08.

7   Wallis MG, Moa E, Zanca F, Leifland K, Danielsson M. Two-view and single-view tomosynthesis versus full-field digital mammography: high-resolution X-ray imaging observer study. Radiology 2012; 262: 788–96.

8   Bernardi D, Ciatto S, Pellegrini M, et al. Prospective study of breast tomosynthesis as a triage to assessment in screening. Breast Cancer Res Treat 2012; 133: 267–71.

9   Michell MJ, Iqbal A, Wasan RK, et al. A comparison of the accuracy of film-screen mammography, full-field digital mammography, and digital breast tomosynthesis. Clin Radiol 2012; 67: 976–81.

10 Skaane P, Gullien R, Bjorndal H, et al. Digital breast tomosynthesis (DBT): initial experience in a clinical setting. Acta Radiol 2012; 53: 524–29.

11 Pellegrini M, Bernardi D, Di MS, et al. Analysis of proportional incidence and review of interval cancer cases observed within the mammography screening programme in Trento province, Italy. Radiol Med 2011; 116: 1217–25.

12 Caumo F, Vecchiato F, Pellegrini M, Vettorazzi M, Ciatto S, Montemezzi S. Analysis of interval cancers observed in an Italian mammography screening programme (2000–2006). Radiol Med 2009; 114: 907–14.

13 Bernardi D, Ciatto S, Pellegrini M, et al. Application of breast tomosynthesis in screening: incremental effect on mammography acquisition and reading time. Br J Radiol 2012; 85: e1174–78.

14 American College of Radiology. ACR BI-RADS: breast imaging reporting and data system, Breast Imaging Atlas. Reston: American College of Radiology, 2003.

15  Lachenbruch PA. On the sample size for studies based on McNemar’s test. Stat Med 1992; 11: 1521–25.

16  Bonett DG, Price RM. Confidence intervals for a ratio of binomial proportions based on paired data. Stat Med 2006; 25: 3039–47.

17  Skaane P, Bandos AI, Gullien R, et al. Comparison of digital mammography alone and digital mammography plus tomosynthesis in a population-based screening program. Radiology 2013; published online Jan 3. http://dx.doi.org/10.1148/ radiol.12121373.

18  The Lancet. The breast cancer screening debate: closing a chapter? Lancet 2012; 380: 1714.

19  Biesheuvel C, Barratt A, Howard K, Houssami N, Irwig L. Effects of study methods and biases on estimates of invasive breast cancer overdetection with mammography screening: a systematic review. Lancet Oncol 2007; 8: 1129–38.

20  Tagliafico A, Astengo D, Cavagnetto F, et al. One-to-one comparison between digital spot compression view and digital breast tomosynthesis. Eur Radiol 2012; 22: 539–44.

21  Tingberg A, Fornvik D, Mattsson S, Svahn T, Timberg P, Zackrisson S. Breast cancer screening with tomosynthesis—initial experiences. Radiat Prot Dosimetry 2011; 147: 180–83.

22  Feng SS, Sechopoulos I. Clinical digital breast tomosynthesis system: dosimetric characterization. Radiology 2012; 263: 35–42.

23  Gur D, Zuley ML, Anello MI, et al. Dose reduction in digital breast tomosynthesis (DBT) screening using synthetically reconstructed projection images: an observer performance study. Acad Radiol 2012; 19: 166–71.

A very good and down-to-earth comment on this article was made by Jules H Sumkin who disclosed that he is an unpaid member of SAB Hologic Inc and have a PI research agreement between University of Pittsburgh and Hologic Inc.

The results of the study by Stefano Ciatto and colleagues1 are consistent with recently published prospective,2,3 retrospective,4 and observational5 reports on the same topic. The study1 had limitations, including the fact that the same radiologist interpreted screens sequentially the same day without cross-balancing which examination was read first. Also, the false-negative findings for integrated 2D and 3D mammography, and therefore absolute benefit from the procedure, could not be adequately assessed because cases recalled by 2D mammography alone (141 cases) did not result in a single detection of an additional cancer while the recalls from the integrated 2D and 3D mammography alone (73 cases) resulted in the detection of 20 additional cancers. Nevertheless, the results are in strong agreement with other studies reporting of substantial performance improvements when the screening is done with integrated 2D and 3D mammography.

I disagree with the conclusion of the study with regards to the urgent need for randomised clinical trials of integrated 2D and 3D versus 2D mammography. First, to assess differences in mortality as a result of an imaging-based diagnostic method, a randomised trial will require several repeated screens by the same method in each study group, and the strong results from all studies to date will probably result in substantial crossover and self-selection biases over time. Second, because of the high survival rate (or low mortality rate) of breast cancer, the study will require long follow-up times of at least 10 years. In a rapidly changing environment in terms of improvements in screening technologies and therapeutic inter­ventions, the avoidance of biases is likely to be very difficult, if not impossible. The use of the number of interval cancers and possible shifts in stage at detection, while appropriately accounting for confounders, would be almost as daunting a task. Third, the imaging detection of cancer is only the first step in many management decisions and interventions that can affect outcome. The appropriate control of biases related to patient management is highly unlikely. The arguments above, in addition to the existing reports to date that show substantial improvements in cancer detection, particularly with the detection of invasive cancers, with a simultaneous reduction in recall rates, support the argument that a randomised trial is neither necessary nor warranted. The current technology might be obsolete by the time results of an appropriately done and analysed randomised trial is made public.

In order to better link the information given by “scientific” papers to the context of daily patients’ reality I suggest to spend some time reviewing few of the videos in the below links:

  1. The following group of videos is featured on a website by Siemens. Nevertheless, the presenting radiologists are leading practitioners who affects thousands of lives every year – What the experts say about tomosynthesis. – click on ECR 2013
  2. Breast Tomosynthesis in Practice – part of a commercial ad of the Washington Radiology Associates featured on the website of Diagnostic Imaging. As well, affects thousands of lives in the Washington area every year.

The pivotal questions yet to be answered are:

  1. What should be done in order to translate increase in sensitivity and early detection into decrease in mortality?

  2. What is the price of such increase in sensitivity in terms of quality of life and health-care costs and is it worth-while to pay?

An article that summarises positively the experience of introducing Tomosynthesis into routine screening practice was recently published on AJR:

Implementation of Breast Tomosynthesis in a Routine Screening Practice: An Observational Study

Stephen L. Rose1, Andra L. Tidwell1, Louis J. Bujnoch1, Anne C. Kushwaha1, Amy S. Nordmann1 and Russell Sexton, Jr.1

Affiliation: 1 All authors: TOPS Comprehensive Breast Center, 17030 Red Oak Dr, Houston, TX 77090.

Citation: American Journal of Roentgenology. 2013;200:1401-1408

 

ABSTRACT :

OBJECTIVE. Digital mammography combined with tomosynthesis is gaining clinical acceptance, but data are limited that show its impact in the clinical environment. We assessed the changes in performance measures, if any, after the introduction of tomosynthesis systems into our clinical practice.

MATERIALS AND METHODS. In this observational study, we used verified practice- and outcome-related databases to compute and compare recall rates, biopsy rates, cancer detection rates, and positive predictive values for six radiologists who interpreted screening mammography studies without (n = 13,856) and with (n = 9499) the use of tomosynthesis. Two-sided analyses (significance declared at p < 0.05) accounting for reader variability, age of participants, and whether the examination in question was a baseline were performed.

RESULTS. For the group as a whole, the introduction and routine use of tomosynthesis resulted in significant observed changes in recall rates from 8.7% to 5.5% (p < 0.001), nonsignificant changes in biopsy rates from 15.2 to 13.5 per 1000 screenings (p = 0.59), and cancer detection rates from 4.0 to 5.4 per 1000 screenings (p = 0.18). The invasive cancer detection rate increased from 2.8 to 4.3 per 1000 screening examinations (p = 0.07). The positive predictive value for recalls increased from 4.7% to 10.1% (p < 0.001).

CONCLUSION. The introduction of breast tomosynthesis into our practice was associated with a significant reduction in recall rates and a simultaneous increase in breast cancer detection rates.

Here are the facts in tables and pictures from this article

Table 1 AJR

Table 2-3 AJR

 

Table 4 AJR

 

p1 ajr

p2 ajr

Other articles related to the management of breast cancer were published on this Open Access Online Scientific Journal:

Automated Breast Ultrasound System (‘ABUS’) for full breast scanning: The beginning of structuring a solution for an acute need!

Introducing smart-imaging into radiologists’ daily practice.

Not applying evidence-based medicine drives up the costs of screening for breast-cancer in the USA.

New Imaging device bears a promise for better quality control of breast-cancer lumpectomies – considering the cost impact

Harnessing Personalized Medicine for Cancer Management, Prospects of Prevention and Cure: Opinions of Cancer Scientific Leaders @ http://pharmaceuticalintelligence.com

Predicting Tumor Response, Progression, and Time to Recurrence

“The Molecular pathology of Breast Cancer Progression”

Personalized medicine gearing up to tackle cancer

What could transform an underdog into a winner?

Mechanism involved in Breast Cancer Cell Growth: Function in Early Detection & Treatment

Nanotech Therapy for Breast Cancer

A Strategy to Handle the Most Aggressive Breast Cancer: Triple-negative Tumors

Breakthrough Technique Images Breast Tumors in 3-D With Great Clarity, Reduced Radiation

Closing the Mammography gap

Imaging: seeing or imagining? (Part 1)

Imaging: seeing or imagining? (Part 2)

Read Full Post »


Controlling focused-treatment of Prostate cancer with MRI

Writer and reporter: Dror Nir, PhD.

In recent years there is a growing trend of treating prostate cancer in a way that will preserve, at least partially, the functionality of this organ. When patients are presenting at biopsy a low-grade localized disease, they might be offered focused treatment of the cancer lesion. One of the option is treatment by high-intensity focused ultrasound (HIFU).

The offering of such treatments created the need of controlling their outcome while the prostate is still inside the patient’s body. The most commonly used protocol is following up the patient’s PSA levels and performing “control” biopsies. The biopsies part is at best case; extremely unpleasant. It also bears some risk for complications.

Therefore, urologists are constantly seeking an imaging based protocol that will enable them to assess the treatment outcome without the need for biopsy. The publication I bring below presents the possibility of using MRI for this task. Although it is not recent, it contains many images that makes the story very clear for the reader.  The main weakness of the study is the small number of patients – only 15.

MR Imaging of Prostate after Treatment with High-Intensity Focused Ultrasound

Alexander P. S. Kirkham, FRCR, Mark Emberton, FRCS, Ivan M. Hoh, MRCS, Rowland O. Illing, MRCS, A. Alex Freeman, FRCP and Clare Allen, FRCR

From the Department of Imaging, University College London Hospitals NHS Foundation Trust, England (A.P.S.K., C.A.); Institute of Urology (M.E., I.M.H., R.O.I.) and Department of Histopathology (A.A.F.), University College London, England.

Address correspondence to A.P.S.K., Imaging Department, University College Hospital, 235 Euston Road, London, England NW1 2BU (e-mail: alexkirkham@yahoo.com).

Radiology March 2008; 246 (3) – 833-844.

Abstract

Purpose: To prospectively evaluate magnetic resonance (MR) imaging findings after high-intensity focused ultrasound (HIFU) treatment of the prostate and to correlate them with clinical and histologic findings.

Materials and Methods: Local ethics committee approval and informed consent were obtained. Fifteen consecutive men aged 46–70 years with organ-confined prostate cancer underwent ultrasonographically guided ablation of the whole prostate. Postoperative MR images were obtained within 1 month (12 patients), at 1–3 months (five patients), and in all patients at 6 months. Prostate volume was measured on T2-weighted images, and enhancing tissue was measured on dynamic images after intravenous administration of gadopentetate dimeglumine. Prostate-specific antigen (PSA) level was measured at regular intervals, and transrectal biopsy was performed in each patient at 6 months after treatment.

Results: Initial post-HIFU images showed a central nonenhancing area, surrounded by an enhancing rim. At 6 months, the prostate was small (median volume reduction, 61%) and was of predominantly low signal intensity on T2-weighted images. The volume of prostate enhancing on the initial posttreatment image correlated well with serum PSA level nadir (Spearman r = 0.90, P < .001) and with volume at 6 months (Pearsonr = 0.80, P = .001). The three patients with the highest volume of enhancing prostate at the initial posttreatment acquisition had persistent cancer at 6-month biopsy.

Conclusion: MR imaging results of the prostate show a consistent sequence of changes after treatment with HIFU and can provide information to the operator about completeness of treatment.

There is currently little to offer men with localized prostate cancer between the two extremes of watchful waiting and radical treatment—most commonly prostatectomy or radiation therapy (1). Ablation of the gland has been proposed as an alternative that has the potential to completely treat the tumor while minimizing the sexual and urinary morbidity that still accompany established radical therapies (2). Several techniques have been used in the prostate—including microwave (3) and radiofrequency (4) ablation, cryotherapy (5), photodynamic therapy (6), and high-intensity focused ultrasound (HIFU) treatment (7).

HIFU is, in several respects, ideally suited to the prostate. In contrast to extracorporeal devices for the liver and kidney (8), with the transrectal approach, there is little movement of the target because of respiration or reflection by overlying bone. A focal distance of 3 or 4 cm allows the generation of coagulative necrosis in treatment voxels less than 0.2 mL and allows a treatment volume that conforms to the shape of the prostate (9)—a degree of precision that may be beyond that of other techniques. Even so, complete ablation is likely to affect periprostatic tissues, including the neurovascular bundles containing the cavernosal nerves (10) and the external urethral sphincter. Preservation of these structures—and the patient’s erectile and urinary function—must be balanced against full treatment of the gland.

Although impotence rates after HIFU treatment approach 50% (11), it is likely that in its current clinical implementation, the prostate is not being fully ablated: In published series, the recurrence rates for cancer range between 25% and 38% (7,11,12). To our knowledge, no groups have reported mean reductions in prostate volume of more than 50% (12,13), and several groups have found it difficult to treat the anterior gland (14).

If we are to improve outcomes, a fundamental requirement for HIFU treatment (and ablative technologies in general) is a method that provides anatomic information to the operator about areas that have been over- or undertreated. This might lead to modifications in future technique, and if obtained soon after treatment, might indicate the need for further ablation. Such a method might also help predict outcome earlier than established measures, such as prostate-specific antigen (PSA) measurement and biopsy.

Magnetic resonance (MR) imaging has great potential in this setting, and Rouviere et al (14) have described the appearance of the prostate on contrast material–enhanced MR images obtained up to 5 months after HIFU treatment. Rouviere et al found a good correlation between the theoretical treatment volume and the volume of nonenhancing prostate on a subsequent acquisition. The aim of our study was to prospectively evaluate MR imaging findings after HIFU treatment of the prostate and to correlate them with clinical and histologic findings.

 

MATERIALS AND METHODS

Misonix (the European distributors of the Sonablate device) funded the phase-II European study and provided equipment and reimbursed the hospital for costs. The company has funded two authors (I.M.H. and R.O.I.) through educational awards. One author (M.E.) has acted as a paid consultant to Misonix and also received honoraria for training and teaching. Authors other than I.M.H., R.O.I., and M.E. had control of the information and data submitted for publication. Misonix was not involved in the analysis of data or the writing of this article.

Patients

We included the first 15 men at University College Hospital (age range, 46–70 years; mean age, 59 years) who were taking part in a registered phase-II multicenter European study of HIFU therapy for organ-confined prostate cancer (Table 1). The study was approved by the local ethics committee, and full written consent was obtained from each patient. The patients understood that HIFU is an experimental treatment whose long-term outcome is unknown and were offered full conventional treatment as an alternative. The study was limited to men with a serum PSA level 15 μg/L or less, Gleason score less than 8, prostate volume less than 40 mL, life expectancy more than 5 years, and age less than 80 years. There was no limit to the number of biopsy cores that had a positive finding or the amount of cancer in each core removed. Patients with a history of previous prostate surgery were excluded, as were men who had undergone androgen deprivation therapy in the 6 months prior to recruitment or had intragland prostatic calcification more than 1 cm in diameter.

Table 1.  Patients and Demographics

 table 1

 * Ratio of cores with a positive finding to cores obtained.

 † Image not available for analysis; volume was calculated by using US measurements.

The Sonablate 500 (Focus Surgery, Indianapolis, Ind) consists of a power generator, water cooling system (the Sonachill), a treatment probe, and a positioning system. The probe contains two curved rectangular piezoceramic transducers with a driving frequency of 4 MHz and focal lengths of 30 and 40 mm. During treatment, these may be driven at low energy to provide real-time diagnostic imaging or at high energy for therapeutic ablation (in situ intensity, 1300–2200 W/cm2). The probe is covered with a condom, under which cold (17°–18°C) degassed water is circulated to help protect the rectum from thermal injury.

Patients were prepared before the procedure with two phosphate enemas to empty the rectum. Oral bowel preparation was used in some patients. Treatment was performed with general anesthesia in the lithotomy position and was performed or closely supervised in every case by an author (M.E., 2 years of experience in HIFU treatment). After gentle dilation of the anal sphincter, the treatment probe was introduced with a covering of ultrasonographic (US) gel to couple it to the rectal mucosa and was held in position with an articulated arm attached to the operating table. A 16-F Foley urethral catheter was inserted using sterile technique, and a 10-mL balloon was inflated to allow the bladder neck and median sagittal plane to be seen accurately. It was removed before treatment began.

Treatment was planned by using US-acquired volumes consisting of stacks of both sagittal and transverse sections (voxel size, 2 × 3 × 30 mm) and was applied in rows that extended in the craniocaudal axis, interleaved to avoid interference from adjacent, recently treated areas. After each 3-second period of ablation, diagnostic transverse and sagittal images in the plane of treatment were obtained to permit tailoring of the energy delivery in the next voxel according to visible changes on the gray-scale image. This is an important difference from the device used by Rouviere’s group (14), in which power is planned before the treatment begins. We aimed to set the power for each voxel at a level that produced hyperechoic change due to cavitation (as described by Illing et al [15]), and we invariably treated the whole anterior prostate. Neurovascular bundles were not identified at treatment (the Sonablate device does not yet have color Doppler capability); rather, we aimed to avoid treating outside the capsule where they lie posterolaterally (10). The time between the first ablation and the point at which treatment was considered complete was 3.0–4.4 hours (mean, 3.6 hours). A 16-F urethral catheter was placed immediately after the treatment and was left in place for 2 weeks.

MR Imaging

For most preoperative examinations and for all post-HIFU imaging, we used an MR machine (Symphony or Avanto; Siemens, Erlangen, Germany) with 1.5-T magnet and a pelvic-phased array coil. Except where stated, a full protocol of T1- and T2-weighted turbo spin-echo (Siemens) images and a dynamic fat-saturated postcontrast volume acquisition were used for both preoperative diagnostic and planning imaging and for postoperative assessment of HIFU treatment (Table 2). The contrast material used was 20 mL of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany) given intravenously at 3 mL/sec.

Table 2. MR Sequences Used at Prostate Imaging

table 2

We aimed to image patients less than 1 month after treatment and did so in 12 patients. The remaining three patients were imaged between 1 and 3 months after treatment. Two patients were imaged in both time periods. Every patient underwent a 6-month MR examination.

Image Analysis

All volume measurements (except where stated) were acquired by using planimetry of contiguous 3-mm sections (16). T2-weighted images were used for measurement of prostatic volume both before and after treatment. The amount of intermediate- or high-signal-intensity material (ie, higher than muscle) remaining within the prostate was also measured on the 6-month posttreatment T2-weighted image.

The volume of nonenhancing prostate tissue at the post-HIFU acquisition was measured by using the final dynamic postcontrast image. On the initial posttreatment image, we also measured the volume of extraprostatic tissue that was both of low signal intensity on the T1-weighted image and nonenhancing. The distance between this tissue and the rectal mucosa was measured at its narrowest point. The mean thickness of the enhancing rim surrounding the treatment volume was measured on transverse postcontrast T1-weighted spin-echo images and was calculated by dividing the area of the rim by its circumference.

The volume of persistently enhancing prostate tissue on the initial image was calculated by subtracting the nonenhancing volume from the total volume of prostate on the T2-weighted image. This could be calculated in 13 patients; one patient did not receive contrast material at the post-HIFU MR acquisition, and the other was imaged more than 2 months after treatment.

All measurements were performed by a first-year radiology fellow (A.P.S.K.) without knowledge of PSA and histologic results. Two other observers independently measured the three key parameters that were used for correlation calculations for each patient: (a) the volume of nonenhancing prostate on the initial image, (b) the total volume of the prostate on the initial image, and (c) the final prostate volume at 6 months. One was a consultant uroradiologist with more than 10 years of experience in the interpretation of prostate MR images (C.A.); the other was a third-year urology research fellow with an interest in prostate imaging (R.O.I.). For each parameter, the mean of the three observers’ measurements was calculated and used for further analysis.

PSA Measurement and Prostate Biopsy

Serum PSA level was measured before and at 1.5, 3, and 6 months after HIFU treatment. The nadir was defined as the lowest of the three values.

Biopsies were performed by an author (A.P.S.K., with 4 years of experience in prostate biopsy) by using a transrectal approach with US guidance and an 18-gauge needle with a 2-cm throw soon after the 6-month MR examination. The number of cores obtained depended on the amount of residual prostate and varied between two and 10 (median, eight cores).

Erectile Function and Continence

The International Index of Erectile Function was used to assess erectile function both before and 3 months after HIFU treatment in each patient (17). The most important question was, “How often were your erections hard enough for penetration [with or without phosphodiesterase type 5 inhibitors]?” A score of 2 (a few times in 4 weeks) to 5 (always) was, for the purposes of this article, considered evidence of intact erectile function.

Men were asked to complete the International Continence Society–validated continence function questionnaire at baseline and at 3 and 6 months after therapy. The question deemed to be most informative was how often the patient required the use of pads or adult diapers. Responses could include “never,” “not more than one per day,” “1–2 per day,” or “more than 3 per day.”

Statistical Analysis

To assess the variance of results between observers, we used the intraclass correlation coefficient (18) applied to measurements obtained by three observers of the calculated volume of enhancing prostate on the initial post-HIFU image and the 6-month prostate volume.

The Spearman rank test was used to assess the correlation between enhancing prostate volume and serum PSA level nadir, and the Pearson test was used to examine the correlation between initial enhancing prostate volume and final prostate volume. Only the patients who were imaged less than 1 month after treatment were included in the analysis. These tests were performed by using software (GraphPad Prism for Mac, version 3; http://www.graphpad.com).

Because some of the covariance of volumes measured after treatment was likely to be due to their correlation with pretreatment prostate volume, we also applied a correction: The values were expressed as a proportion of the pretreatment volume, and a further correlation measurement was performed by using the Pearson test. In each case, a P value of less than .02 was considered to indicate a significant difference.

 

RESULTS

Up to 1 Month After Treatment

T2-weighted images.—Compared with that on the preoperative image, the prostate volume increased in every case (Table 1 and Table E1, Fig 1). The signal intensity from the prostate on T2-weighted images within the first month was always heterogeneous and variable. It was impossible to predict from the findings on T2-weighted images which areas of the prostate would enhance after intravenous contrast material administration. The periprostatic fat was also heterogeneous in signal intensity, which was consistent with edema (Fig 2).

Figure 1: Graph of change in prostate volume after HIFU treatment. Volume rises initially (less than 1 month after treatment) and is reduced in all cases at 6 months. Numbers = patient numbers.

 Picture1

Figure 2: MR images in patient 1 (a–d) and (e–h) patient 8 show low volume of enhancing prostate at initial imaging and small residual prostate at 6 months. Posttreatment serum PSA level was less than 0.05 μg/L in both cases.

Figure 2a:

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Figure 2b:

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Figure 2c:

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Figure 2d:

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Figure 2e:

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Figure 2f:

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Figure 2g:

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Figure 2h:

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T1-weighted images.—The prostate was of predominantly low signal intensity, although patchy areas of intermediate or high signal intensity, likely to represent hemorrhage, were a constant finding within the gland and in all but one of 28 seminal vesicles.

Postcontrast images.—In each patient, the postcontrast images showed a central area of nonenhancing tissue. This conformed to the treatment volume and was surrounded by an enhancing rim of mean thickness of 2–8 mm (median, 4 mm) that was continuous around the prostate in most patients (Fig 2; Table E1,).

The enhancing prostate varied in size and position. Part of the enhancing rim usually lay within the prostatic capsule and continued to the prostatic apex where there was almost always some enhancing tissue between the nonenhancing prostate and the external urethral sphincter. In many patients, more central areas of enhancement were seen: at the apex or base, either posteriorly or anteriorly (Table E1), and were almost always in continuity with the rim.

In every patient, the nonenhancing, low signal intensity within the prostate extended outside the gland and involved the periprostatic fat and the levator ani muscle, particularly anterolaterally (Table E1, Figs 23). This varied considerably and tended to be most prominent in those who had no residual gland enhancement and had an undetectable serum PSA level after HIFU treatment (Table E1). In several patients, the nonenhancing area extended to involve the Denonvilliers fascia. (The distance between its margin and the rectal muscle is listed in Table E1.) In one patient, a proportion of the rectal wall enhanced avidly, but in no patient was there loss of rectal wall enhancement to suggest necrosis.

Figure 3: MR images obtained near the prostate apex show incomplete treatment and persisting high signal intensity in prostate. Serum PSA level nadir = 0.61 μg/L.

Figure 3a: Patient 4:

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 Figure 3b: Patient 4:

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Figure 3c: Patient 4:

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Figure 3d: Patient 4:

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At 1–3 Months

In three patients, there was a “double rim” (Fig 4) on postcontrast images obtained at 36 and 56 days after HIFU treatment. The inner component lay within the prostate and the outer at the prostatic capsule; the intervening part was of low signal intensity on both T1- and T2-weighted images.

 Figure 4: MR images of “double rim” at 56 days after HIFU treatment.

Figure 4a: Patient 3:

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Figure 4b: Patient 3:

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Figure 4c: Patient 3:

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Six-month Appearance

T2-weighted images.—In every patient, the volume of the prostate was reduced by more than 45% (median, 61% reduction) (Table E1). On T2-weighted images, the majority of the persisting prostate was of low signal intensity, with poor definition to the capsule and with persisting heterogeneous signal intensity to the surrounding fat. However, in 12 of 15 patients, there was persisting high or intermediate signal intensity of the prostate—up to 5.34 mL in volume and most often seen posteriorly and at the apex (Table E1, Figs 3 and 5). In many patients (for example, those in Fig 2), low-signal-intensity prostate of reduced volume surrounded a capacious prostatic cavity continuous with the urethra, which is similar to the cavity seen after transurethral resection (19).

Figure 5: MR images of incomplete treatment of tumor and positive biopsy findings in three of 10 cores at 6 months (in right lateral midzone, right lateral base, and right parasagittal base samples). Serum PSA level nadir = 1.19 μg/L.

Figure 5a: Patient 13:

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Figure 5b: Patient 13:

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Figure 5c: Patient 13:

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Figure 5d: Patient 13:

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Figure 5e: Patient 13:

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Postcontrast images.—Some small areas of nonenhancing tissue persisted in eight of 14 patients, but this was less than 1 mL in all but one (patient 13, in whom 4 mL of the gland volume of 18.7 mL was nonenhancing). The levator muscle showed a normal signal intensity.

Correlation Between Initial Imaging and Later Findings

In the 12 patients who underwent the initial acquisition within 1 month of HIFU treatment, the volume of enhancing tissue on the initial posttreatment image was positively correlated with the serum PSA level nadir (Fig 6) (Spearman r = 0.90, P < .001) and with the amount of residual tissue at 6 months (including all low-signal-intensity material that was likely to represent fibrosis or necrosis) (Fig 7) (Pearson r = 0.80, P = .001).

 Figure 6: Graph of relationship between the proportion of the prostate still enhancing on initial image and serum PSA level nadir. There is a significant positive correlation (Spearman r = 0.90, P < .001). * = patient 13, who was included in graph but not in analysis (imaged 56 days after HIFU treatment). Patients 14 and 15 are not included because they did not undergo contrast-enhanced acquisition within 2 months of HIFU treatment. μgl−1 = μg/L.

 Picture6

Figure 7: Graph of relationship between the proportion of the prostate still enhancing on initial image and final volume of prostate. There is a significant positive correlation between the variables (Pearson r = 0.80, P = .001). * = patient 13, who was included in graph but not in analysis (imaged 56 days after HIFU treatment). Patients 14 and 15 are not included because they did not undergo contrast-enhanced acquisition within 2 months of HIFU treatment.

Picture7

When posttreatment volumes are expressed as a proportion of pretreatment prostate volume, the correlation between enhancing tissue volume on the initial posttreatment image and the 6-month prostate volume persists (Pearson r = 0.70, P = .001).

Interobserver Correlation

The interobserver variation was excellent for the calculated volume of prostate enhancing on the initial post-HIFU image, with an intraclass correlation coefficient of 0.92, and was good for final prostate volume (intraclass correlation coefficient = 0.73).

Clinical Findings

In five patients (patients 1, 3, 8, 11, and 13), there was imaging evidence (at MR imaging or retrograde urethrography) of a stricture in the mid- or distal prostatic urethra, which was confirmed by using flow rate studies and treated by using self-catheterization or with graded urethral dilators. None have required formal urethrotomy. Patient 14 developed a bladder neck stricture, which was treated successfully by incision.

Before treatment, no men required pads or adult diapers for incontinence. At 6 months after the treatment, four men still required not more than one pad per day. In two cases, this was for reassurance rather than actual leakage.

In the 14 patients in whom there was intact erectile function (score 2–5 for the question, “How often were your erections hard enough for penetration?”) before HIFU treatment, it was intact in nine patients after the procedure. One patient had stopped trying to achieve erections, and four could not achieve penetration.

Histologic Findings

In the three patients in whom there was no high-signal-intensity peripheral zone at 6 months and with serum PSA level less than 0.05 μg/L, there was either no prostatic tissue or only a small group of acini in one core. The remaining patients had a variable amount of residual prostate at core biopsy.

Five patients had residual tumor. In three patients, it was seen in at least two cores (Table E1), and these three patients also had the largest volume of enhancing prostate on the initial post-HIFU MR image (Figs 6 and 7) and more than 2 mL of intermediate- or high-signal-intensity gland on T2-weighted images at 6 months.

In four of five patients with residual cancer, it could not be identified on either contrast-enhanced or T2-weighted images. In one patient (Fig 4), the early dynamic images showed prominent enhancement in the anterior gland, which was consistent with residual cancer found at the distal (ie, nonrectal) end of three right-sided biopsy cores. Such enhancement was not seen in patients with no cancer found at core biopsy.

 

DISCUSSION

We found a consistent sequence of changes at MR imaging after HIFU treatment of the whole prostate. The proportion of enhancing tissue on the initial posttreatment MR image was predictive of gland volume at 6 months and serum PSA level nadir. A strong statistical relationship between the latter and outcome has recently been demonstrated (20).

Most patients with residual cancer had evidence of incomplete ablation early (a large volume of enhancing prostate on the initial image) and late (a large volume of high-signal-intensity residual prostate on T2-weighted images at 6 months).

In some patients it was possible to achieve an undetectable serum PSA level at 6 months and entirely low signal intensity on T2-weighted images in the region of the prostate. These patients had either no or a small amount of viable prostate in one core at biopsy.

Conversely, in spite of reductions in prostate volume of more than 45% at 6 months, the majority of patients had histologic evidence of persisting viable prostate, and in a group of patients with organ-confined disease but no limit to the volume of cancer pretreatment, one-third had evidence of residual tumor.

Persisting enhancing prostatic tissue usually occurred at the periphery (or extended toward the center of the gland from it) and was particularly common at the apex and near the rectum.

Results of one previously published study (14) of post-HIFU appearances with MR imaging show a similar sequence of acute changes, although there was no attempt to quantify prostate volume at 6 months. There is also a large body of work on the MR imaging appearances with thermotherapy (whether laser [21,22] or radiofrequency [23]) and cryotherapy (24) within the prostate and other organs. The hyperenhancing rim of tissue is a constant finding in several tissues, including the liver (25), the kidney (26), and the brain (27). In the liver and the kidney, it is thin (1 mm or less) and, in most cases, has disappeared by 2 months after ablation (28). Within the prostate, the hyperenhancing rim has been shown to occur after laser ablation of benign prostatic hyperplasia (21,22) and after HIFU treatment (14).

Histologic evidence in animal models—including rabbit and porcine liver (29)—suggests that the enhancing rim corresponds to an area of inflammation and then fibrosis, with a variable amount of residual, viable tissue. How much of the rim will be viable after ablation of the prostate in humans remains uncertain. On the one hand, after HIFU treatment, core biopsy results show “partial or complete necrosis” in the rim (14). On the other, after laser ablation of benign prostatic hyperplasia, the volume of coagulative necrosis at histologic examination correlates very well with the central nonenhancing region at MR imaging, not including the rim (22). The answer is likely to be that a variable amount of the rim contains viable tissue (depending on the organ being imaged [30], the nature of the treatment, and the interval before the acquisition), and the implication is that the only reliably necrotic area at MR imaging is that which does not enhance. We have avoided the term necrosis for the nonenhancing areas of prostate seen in our current study, but from these data it is likely that the areas of prostate without enhancement are truly necrotic.

The distribution of enhancing prostate on posttreatment MR images fits with histologic evidence that “ventral, lateral and dorsal sides of the prostate” have residual viable prostatic tissue at histologic examination after HIFU treatment (31). What all of these areas have in common is proximity to the more richly vascular prostatic capsule. Is it possible that increased vascularity here results in reduced efficacy? This is another area that has been addressed by Rouviere’s group (32), who did not find a correlation between successful ablation and prostate vascularity by using power Doppler US; they conclude, as others have (33,34), that short (3-second) high-intensity bursts of focused ultrasound are unlikely to be markedly affected by blood flow. An alternate explanation is a geometric one: Centrally lying voxels are easier to treat because they may be rendered necrotic either by direct treatment or by damage to supplying vessels in the periphery.

An implication of these results is that the best strategies for minimizing complications while ensuring destruction of the cancer are likely to involve a degree of targeting: If the tumor can be imaged with MR imaging, the patient might be treated with higher power and wider margins (including periprostatic fat, muscle, or even neurovascular bundles) at the site of the cancer and with a standard intensity to the rest of the gland. An analogous approach is the wide excision, including a unilateral neurovascular bundle, of bulky tumors at radical prostatectomy (35). Such an approach may well have benefited our patients 7 and 13.

One methodologic issue that is currently unresolved relates to the timing of MR imaging. A detailed within-patient study of MR imaging changes after HIFU treatment is needed to properly describe the longitudinal changes in the appearance of the prostate. Rouviere et al (14) found that the area of nonenhancing tissue decreases by 50% at 1 month compared with that at an immediate (<1 week) post-HIFU acquisition, which suggests that for an accurate assessment of necrosis volume, the prostate should be imaged as soon as possible after treatment. Of course, perfusion would ideally be assessed during HIFU treatment so that undertreated areas could be further ablated. There is some evidence that Doppler or contrast-enhanced US (36) could play this role, but, to our knowledge, there are no studies on the correlation of immediate findings with later clinical data, such as serum PSA level or histologic examination.

We used fast low-angle shot sequences to assess enhancement because we found that the subjective assessment (together with objective measurements of signal intensity) of the dynamic series helped us identify truly nonenhancing tissue. However, the T1-weighted spin-echo postcontrast sequence would have been adequate, and we consider, as others do (22), dynamic contrast-enhanced sequences not to be an essential part of the protocol for postablation assessment. What is certain is that unenhanced T2-weighted sequences are inadequate for assessing necrosis (14,22).

Our results differ from those of other published series of HIFU treatment in the marked reduction in gland volume and absence of zonal anatomy in many patients observed at 6 months. In contrast to the study of post-HIFU MR imaging by Rouviere et al (14) who used a different device, we did not find that “HIFU-induced abnormalities seem to disappear within 3–5 months.” Rather, in several patients, it was difficult to discern any residual prostate at all at both MR and US studies. The difference probably lies in the power used for treatment and the completeness of gland coverage. The stricture rate of six of 15 is high when compared with that in published series (7,37,38) and may be related to the power used, the degree of fibrosis occurring in the prostate, and the strategy for catheterization. The latter is considered likely to be important, and we have recently changed to using a suprapubic catheter (rather than urethral) after treatment. The rate of impotence after treatment is similar to that in published series (11), as is grade I incontinence.

Our work has implications for the conduct of HIFU. The finding that the volume of enhancing prostate on the initial posttreatment image correlates well with intermediate measures, such as serum PSA level nadir and biopsy evidence of residual cancer, suggests that MR imaging can provide the operator with feedback on the effectiveness of the intervention. This information might enable modification of the technique to treat areas that have been incompletely ablated in previous patients—in our series, those areas encompassed the apex and posterior gland and rarely anterior tissue (in contrast to other study results [14]). Conversely, we might have reduced power or treatment volume at the anterolateral aspect of the gland adjacent to the levator muscle. Such feedback has been cited as a desirable attribute for ablation technology (39) and up to now has been missing.

Our study had several limitations. Although it is likely that nonenhancing areas at MR imaging represent necrosis, we do not have direct histologic evidence. Sampling error and misregistration limit the utility of core biopsies in this context. We have shown that the MR imaging appearances soon after HIFU treatment correlate with findings at 6 months, but this is not the same as outcome. A considerably longer follow-up and a larger number of patients will be necessary to determine both the ultimate efficacy of HIFU treatment and the ability of MR imaging to help predict outcome. Last, while our findings suggest that MR imaging soon after treatment may be useful to assess areas of under- and overtreatment, this is not real-time feedback and does not allow modification of the treatment as it progresses.

In summary, MR imaging results in the first 6 months after HIFU treatment show a consistent sequence of changes, and appearances in the 1st month correlate with serum PSA level nadir and imaging findings at 6 months. Such imaging results hold promise for providing feedback to the operator about the effectiveness of treatment.

 

ADVANCES IN KNOWLEDGE

  • Treatment of prostate cancer by using ablation with high-intensity focused ultrasound (HIFU) results in a consistent series of changes within the gland during 6 months seen at contrast-enhanced MR imaging.
  • Within 1 month after treatment, a central nonenhancing area is surrounded by an enhancing rim of tissue lying variably within and outside the prostate.
  • At 6 months, the gland is markedly smaller and of partly or completely low signal intensity on T2-weighted images.
  • The amount of enhancing prostate on the initial image correlates with several findings at 6 months, including serum prostate-specific antigen level nadir and prostate volume.

 

IMPLICATION FOR PATIENT CARE

  • MR imaging after HIFU treatment may provide information about completeness of tumor ablation and the need for early retreatment or close monitoring in cases of incomplete coverage.

 

Footnotes

  • Trial registration: This trial started recruiting before the trial registration requirements of the International Committee of Medical Journal Editors were formalized.

See Materials and Methods for pertinent disclosures.

Author contributions: Guarantors of integrity of entire study, A.P.S.K., I.M.H., C.A.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, A.P.S.K., M.E., I.M.H., R.O.I., C.A.; clinical studies, A.P.S.K., R.O.I., C.A.; statistical analysis, A.P.S.K.; and manuscript editing, all authors

Abbreviations:HIFU = high-intensity focused ultrasoundPSA = prostate-specific antigen

 

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