Imaging Technology in Cancer Surgery
Author and curator: Dror Nir, PhD
The advent of medical-imaging technologies such as image-fusion, functional-imaging and noninvasive tissue characterisation is playing an imperative role in answering this demand thus transforming the concept of personalized medicine in cancer into practice. The leading modality in that respect is medical imaging. To date, the main imaging systems that can provide reasonable level of cancer detection and localization are: CT, mammography, Multi-Sequence MRI, PET/CT and ultrasound. All of these require skilled operators and experienced imaging interpreters in order to deliver what is required at a reasonable level. It is generally agreed by radiologists and oncologists that in order to provide a comprehensive work-flow that complies with the principles of personalized medicine, future cancer patients’ management will heavily rely on computerized image interpretation applications that will extract from images in a standardized manner measurable imaging biomarkers leading to better clinical assessment of cancer patients.
As consequence of the human genome project and technological advances in gene-sequencing, the understanding of cancer advanced considerably. This led to increase in the offering of treatment options. Yet, surgical resection is still the leading form of therapy offered to patients with organ confined tumors. Obtaining “cancer free” surgical margins is crucial to the surgery outcome in terms of overall survival and patients’ quality of life/morbidity. Currently, a significant portion of surgeries ends up with positive surgical margins leading to poor clinical outcome and increase of costs. To improve on this, large variety of intraoperative imaging-devices aimed at resection-guidance have been introduced and adapted in the last decade and it is expected that this trend will continue.
The Status of Contemporary Image-Guided Modalities in Oncologic Surgery is a review paper presenting a variety of cancer imaging techniques that have been adapted or developed for intra-operative surgical guidance. It also covers novel, cancer-specific contrast agents that are in early stage development and demonstrate significant promise to improve real-time detection of sub-clinical cancer in operative setting.
Another good (free access) review paper is: uPAR-targeted multimodal tracer for pre- and intraoperative imaging in cancer surgery
Abstract
Pre- and intraoperative diagnostic techniques facilitating tumor staging are of paramount importance in colorectal cancer surgery. The urokinase receptor (uPAR) plays an important role in the development of cancer, tumor invasion, angiogenesis, and metastasis and over-expression is found in the majority of carcinomas. This study aims to develop the first clinically relevant anti-uPAR antibody-based imaging agent that combines nuclear (111In) and real-time near-infrared (NIR) fluorescent imaging (ZW800-1). Conjugation and binding capacities were investigated and validated in vitro using spectrophotometry and cell-based assays. In vivo, three human colorectal xenograft models were used including an orthotopic peritoneal carcinomatosis model to image small tumors. Nuclear and NIR fluorescent signals showed clear tumor delineation between 24h and 72h post-injection, with highest tumor-to-background ratios of 5.0 ± 1.3 at 72h using fluorescence and 4.2 ± 0.1 at 24h with radioactivity. 1-2 mm sized tumors could be clearly recognized by their fluorescent rim. This study showed the feasibility of an uPAR-recognizing multimodal agent to visualize tumors during image-guided resections using NIR fluorescence, whereas its nuclear component assisted in the pre-operative non-invasive recognition of tumors using SPECT imaging. This strategy can assist in surgical planning and subsequent precision surgery to reduce the number of incomplete resections.
INTRODUCTION
Diagnosis, staging, and surgical planning of colorectal cancer patients increasingly rely on imaging techniques that provide information about tumor biology and anatomical structures [1-3]. Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are preoperative nuclear imaging modalities used to provide insights into tumor location, tumor biology, and the surrounding micro-environment [4]. Both techniques depend on the recognition of tumor cells using radioactive ligands. Various monoclonal antibodies, initially developed as therapeutic agents (e.g. cetuximab, bevacizumab, labetuzumab), are labeled with radioactive tracers and evaluated for pre-operative imaging purposes [5-9]. Despite these techniques, during surgery the surgeons still rely mostly on their eyes and hands to distinguish healthy from malignant tissues, resulting in incomplete resections or unnecessary tissue removal in up to 27% of rectal cancer patients [10, 11]. Incomplete resections (R1) are shown to be a strong predictor of development of distant metastasis, local recurrence, and decreased survival of colorectal cancer patients [11, 12]. Fluorescence-guided surgery (FGS) is an intraoperative imaging technique already introduced and validated in the clinic for sentinel lymph node (SLN) mapping and biliary imaging [13]. Tumor-specific FGS can be regarded as an extension of SPECT/PET, using fluorophores instead of radioactive labels conjugated to tumor-specific ligands, but with higher spatial resolution than SPECT/PET imaging and real-time anatomical feedback [14]. A powerful synergy can be achieved when nuclear and fluorescent imaging modalities are combined, extending the nuclear diagnostic images with real-time intraoperative imaging. This combination can lead to improved diagnosis and management by integrating pre-intra and postoperative imaging. Nuclear imaging enables pre-operative evaluation of tumor spread while during surgery deeper lying spots can be localized using the gamma probe counter. The (NIR) fluorescent signal aids the surgeon in providing real-time anatomical feedback to accurately recognize and resect malignant tissues. Postoperative, malignant cells can be recognized using NIR fluorescent microscopy. Clinically, the advantages of multimodal agents in image-guided surgery have been shown in patients with melanoma and prostate cancer, but those studies used a-specific agents, following the natural lymph drainage pattern of colloidal tracers after peritumoral injection [15, 16]. The urokinase-type plasminogen activator receptor (uPAR) is implicated in many aspects of tumor growth and (micro) metastasis [17, 18]. The levels of uPAR are undetectable in normal tissues except for occasional macrophages and granulocytes in the uterus, thymus, kidneys and spleen [19]. Enhanced tumor levels of uPAR and its circulating form (suPAR) are independent prognostic markers for overall survival in colorectal cancer patients [20, 21]. The relatively selective and high overexpression of uPAR in a wide range of human cancers including colorectal, breast, and pancreas nominate uPAR as a widely applicable and potent molecular target [17,22]. The current study aims to develop a clinically relevant uPAR-specific multimodal agent that can be used to visualize tumors pre- and intraoperatively after a single injection. We combined the 111Indium isotope with NIR fluorophore ZW800-1 using a hybrid linker to an uPAR specific monoclonal antibody (ATN-658) and evaluated its performance using a pre-clinical SPECT system (U-SPECT-II) and a clinically-applied NIR fluorescence camera system (FLARE™).
Robotic surgery is a growing trend as a form of surgery, specifically in urology. The following review paper propose a good discussion on the added value of imaging in urologic robotic surgery:
The current and future use of imaging in urological robotic surgery: a survey of the European Association of Robotic Urological Surgeons
Abstract
Background
With the development of novel augmented reality operating platforms the way surgeons utilize imaging as a real-time adjunct to surgical technique is changing.
Methods
A questionnaire was distributed via the European Robotic Urological Society mailing list. The questionnaire had three themes: surgeon demographics, current use of imaging and potential uses of an augmented reality operating environment in robotic urological surgery.
Results
117 of the 239 respondents (48.9%) were independently practicing robotic surgeons. 74% of surgeons reported having imaging available in theater for prostatectomy 97% for robotic partial nephrectomy and 95% cystectomy. 87% felt there was a role for augmented reality as a navigation tool in robotic surgery.
Conclusions
This survey has revealed the contemporary robotic surgeon to be comfortable in the use of imaging for intraoperative planning it also suggests that there is a desire for augmented reality platforms within the urological community. Copyright © 2014 John Wiley & Sons, Ltd.
Introduction
Since Röntgen first utilized X-rays to image the carpal bones of the human hand in 1895, medical imaging has evolved and is now able to provide a detailed representation of a patient’s intracorporeal anatomy, with recent advances now allowing for 3-dimensional (3D) reconstructions. The visualization of anatomy in 3D has been shown to improve the ability to localize structures when compared with 2D with no change in the amount of cognitive loading [1]. This has allowed imaging to move from a largely diagnostic tool to one that can be used for both diagnosis and operative planning.
One potential interface to display 3D images, to maximize its potential as a tool for surgical guidance, is to overlay them onto the endoscopic operative scene (augmented reality). This addresses, in part, a criticism often leveled at robotic surgery, the loss of haptic feedback. Augmented reality has the potential to mitigate this sensory loss by enhancing the surgeons visual cues with information regarding subsurface anatomical relationships [2].
Augmented reality surgery is in its infancy for intra-abdominal procedures due in large part to the difficulties of applying static preoperative imaging to a constantly deforming intraoperative scene [3]. There are case reports and ex vivo studies in the literature examining the technology in minimal access prostatectomy [3-6] and partial nephrectomy [7-10], but there remains a lack of evidence determining whether surgeons feel there is a role for the technology and if so for what procedures they feel it would be efficacious.
This questionnaire-based study was designed to assess first, the pre- and intra-operative imaging modalities utilized by robotic urologists; second, the current use of imaging intraoperatively for surgical planning; and finally whether there is a desire for augmented reality among the robotic urological community.
Methods
Recruitment
A web based survey instrument was designed and sent out, as part of a larger survey, to members of the EAU robotic urology section (ERUS). Only independently practicing robotic surgeons performing robot-assisted laparoscopic prostatectomy (RALP), robot-assisted partial nephrectomy (RAPN) and/or robotic cystectomy were included in the analysis, those surgeons exclusively performing other procedures were excluded. Respondents were offered no incentives to reply. All data collected was anonymous.
Survey design and administration
The questionnaire was created using the LimeSurvey platform (www.limesurvey.com) and hosted on their website. All responses (both complete and incomplete) were included in the analysis. The questionnaire was dynamic with the questions displayed tailored to the respondents’ previous answers.
When computing fractions or percentages the denominator was the number of respondents to answer the question, this number is variable due to the dynamic nature of the questionnaire.
Demographics
All respondents to the survey were asked in what country they practiced and what robotic urological procedures they performed. In addition to what procedures they performed surgeons were asked to specify the number of cases they had undertaken for each procedure.
Current imaging practice
Procedure-specific questions in this group were displayed according to the operations the respondent performed. A summary of the questions can be seen in Appendix 1. Procedure-nonspecific questions were also asked. Participants were asked whether they routinely used the Tile Pro™ function of the da Vinci console (Intuitive Surgical, Sunnyvale, USA) and whether they routinely viewed imaging intra-operatively.
Augmented reality
Before answering questions in this section, participants were invited to watch a video demonstrating an augmented reality platform during RAPN, performed by our group at Imperial College London. A still from this video can be seen in Figure 1. They were then asked whether they felt augmented reality would be of use as a navigation or training tool in robotic surgery.
Figure 1. A still taken from a video of augmented reality robot assisted partial nephrectomy performed. Here the tumour has been painted into the operative view allowing the surgeon to appreciate the relationship of the tumour with the surface of the kidney
Once again, in this section, procedure-specific questions were displayed according to the operations the respondent performed. Only those respondents who felt augmented reality would be of use as a navigation tool were asked procedure-specific questions. Questions were asked to establish where in these procedures they felt an augmented reality environment would be of use.
Results
Demographics
Of the 239 respondents completing the survey 117 were independently practising robotic surgeons and were therefore eligible for analysis. The majority of the surgeons had both trained (210/239, 87.9%) and worked in Europe (215/239, 90%). The median number of cases undertaken by those surgeons reporting their case volume was: 120 (6–2000), 9 (1–120) and 30 (1–270), for RALP, robot assisted cystectomy and RAPN, respectively.
Contemporary use of imaging in robotic surgery
When enquiring about the use of imaging for surgical planning, the majority of surgeons (57%, 65/115) routinely viewed pre-operative imaging intra-operatively with only 9% (13/137) routinely capitalizing on the TilePro™ function in the console to display these images. When assessing the use of TilePro™ among surgeons who performed RAPN 13.8% (9/65) reported using the technology routinely.
When assessing the imaging modalities that are available to a surgeon in theater the majority of surgeons performing RALP (74%, 78/106)) reported using MRI with an additional 37% (39/106) reporting the use of CT for pre-operative staging and/or planning. For surgeons performing RAPN and robot-assisted cystectomy there was more of a consensus with 97% (68/70) and 95% (54/57) of surgeons, respectively, using CT for routine preoperative imaging (Table 1).
Table 1. Which preoperative imaging modalities do you use for diagnosis and surgical planning?
| |
CT |
MRI |
USS |
None |
Other |
| RALP (n = 106) |
39.8% |
73.5% |
2% |
15.1% |
8.4% |
| (39) |
(78) |
(3) |
(16) |
(9) |
| RAPN (n = 70) |
97.1% |
42.9% |
17.1% |
0% |
2.9% |
| (68) |
(30) |
(12) |
(0) |
(2) |
| Cystectomy (n = 57) |
94.7% |
26.3% |
1.8% |
1.8% |
5.3% |
| (54) |
(15) |
(1) |
(1) |
(3) |
Those surgeons performing RAPN were found to have the most diversity in the way they viewed pre-operative images in theater, routinely viewing images in sagittal, coronal and axial slices (Table 2). The majority of these surgeons also viewed the images as 3D reconstructions (54%, 38/70).
Table 2. How do you typically view preoperative imaging in the OR? 3D recons = three-dimensional reconstructions
| |
Axial slices (n) |
Coronal slices (n) |
Sagittal slices (n) |
3D recons. (n) |
Do not view (n) |
|
| RALP (n = 106) |
49.1% |
44.3% |
31.1% |
9.4% |
31.1% |
|
| (52) |
(47) |
(33) |
(10) |
(33) |
|
| RAPN (n = 70) |
68.6% |
74.3% |
60% (42) |
54.3% |
0% |
|
| (48) |
(52) |
|
(38) |
(0) |
|
| Cystectomy (n = 57) |
70.2% |
52.6% |
50.9% |
21.1% |
8.8% |
|
| (40) |
(30) |
(29) |
(12) |
(5) |
|
The majority of surgeons used ultrasound intra-operatively in RAPN (51%, 35/69) with a further 25% (17/69) reporting they would use it if they had access to a ‘drop-in’ ultrasound probe (Figure 2).
Figure 2. Chart demonstrating responses to the question – Do you use intraoperative ultrasound for robotic partial nephrectomy?
Desire for augmented reality
Overall, 87% of respondents envisaged a role for augmented reality as a navigation tool in robotic surgery and 82% (88/107) felt that there was an additional role for the technology as a training tool.
The greatest desire for augmented reality was among those surgeons performing RAPN with 86% (54/63) feeling the technology would be of use. The largest group of surgeons felt it would be useful in identifying tumour location, with significant numbers also feeling it would be efficacious in tumor resection (Figure 3).
Figure 3. Chart demonstrating responses to the question – In robotic partial nephrectomy which parts of the operation do you feel augmented reality image overlay would be of assistance?
When enquiring about the potential for augmented reality in RALP, 79% (20/96) of respondents felt it would be of use during the procedure, with the largest group feeling it would be helpful for nerve sparing 65% (62/96) (Figure 4). The picture in cystectomy was similar with 74% (37/50) of surgeons believing augmented reality would be of use, with both nerve sparing and apical dissection highlighted as specific examples (40%, 20/50) (Figure 5). The majority also felt that it would be useful for lymph node dissection in both RALP and robot assisted cystectomy (55% (52/95) and 64% (32/50), respectively).
Figure 4. Chart demonstrating responses to the question – In robotic prostatectomy which parts of the operation do you feel augmented reality image overlay would be of assistance?
Figure 5. Chart demonstrating responses to the question – In robotic cystectomy which parts of the operation do you feel augmented reality overlay technology would be of assistance?
Discussion
The results from this study suggest that the contemporary robotic surgeon views imaging as an important adjunct to operative practice. The way these images are being viewed is changing; although the majority of surgeons continue to view images as two-dimensional (2D) slices a significant minority have started to capitalize on 3D reconstructions to give them an improved appreciation of the patient’s anatomy.
This study has highlighted surgeons’ willingness to take the next step in the utilization of imaging in operative planning, augmented reality, with 87% feeling it has a role to play in robotic surgery. Although there appears to be a considerable desire for augmented reality, the technology itself is still in its infancy with the limited evidence demonstrating clinical application reporting only qualitative results [3, 7, 11, 12].
There are a number of significant issues that need to be overcome before augmented reality can be adopted in routine clinical practice. The first of these is registration (the process by which two images are positioned in the same coordinate system such that the locations of corresponding points align [13]). This process has been performed both manually and using automated algorithms with varying degrees of accuracy [2, 14]. The second issue pertains to the use of static pre-operative imaging in a dynamic operative environment; in order for the pre-operative imaging to be accurately registered it must be deformable. This problem remains as yet unresolved.
Live intra-operative imaging circumvents the problems of tissue deformation and in RAPN 51% of surgeons reported already using intra-operative ultrasound to aid in tumour resection. Cheung and colleagues [9] have published an ex vivo study highlighting the potential for intra-operative ultrasound in augmented reality partial nephrectomy. They report the overlaying of ultrasound onto the operative scene to improve the surgeon’s appreciation of the subsurface tumour anatomy, this improvement in anatomical appreciation resulted in improved resection quality over conventional ultrasound guided resection [9]. Building on this work the first in vivo use of overlaid ultrasound in RAPN has recently been reported [10]. Although good subjective feedback was received from the operating surgeon, the study was limited to a single case demonstrating feasibility and as such was not able to show an outcome benefit to the technology [10].
RAPN also appears to be the area in which augmented reality would be most readily adopted with 86% of surgeons claiming they see a use for the technology during the procedure. Within this operation there are two obvious steps to augmentation, anatomical identification (in particular vessel identification to facilitate both routine ‘full clamping’ and for the identification of secondary and tertiary vessels for ‘selective clamping’ [15]) and tumour resection. These two phases have different requirements from an augmented reality platform; the first phase of identification requires a gross overview of the anatomy without the need for high levels of registration accuracy. Tumor resection, however, necessitates almost sub-millimeter accuracy in registration and needs the system to account for the dynamic intra-operative environment. The step of anatomical identification is amenable to the use of non-deformable 3D reconstructions of pre-operative imaging while that of image-guided tumor resection is perhaps better suited to augmentation with live imaging such as ultrasound [2, 9, 16].
For RALP and robot-assisted cystectomy the steps in which surgeons felt augmented reality would be of assistance were those of neurovascular bundle preservation and apical dissection. The relative, perceived, efficacy of augmented reality in these steps correlate with previous examinations of augmented reality in RALP [17, 18]. Although surgeon preference for utilizing augmented reality while undertaking robotic prostatectomy has been demonstrated, Thompson et al. failed to demonstrate an improvement in oncological outcomes in those patients undergoing AR RALP [18].
Both nerve sparing and apical dissection require a high level of registration accuracy and a necessity for either live imaging or the deformation of pre-operative imaging to match the operative scene; achieving this level of registration accuracy is made more difficult by the mobilization of the prostate gland during the operation [17]. These problems are equally applicable to robot-assisted cystectomy. Although guidance systems have been proposed in the literature for RALP [3-5, 12, 17], none have achieved the level of accuracy required to provide assistance during nerve sparing. In addition, there are still imaging challenges that need to be overcome. Although multiparametric MRI has been shown to improve decision making in opting for a nerve sparing approach to RALP [19] the imaging is not yet able to reliably discern the exact location of the neurovascular bundle. This said, significant advances are being made with novel imaging modalities on the horizon that may allow for imaging of the neurovascular bundle in the near future [20].
Limitations
The number of operations included represents a significant limitation of the study, had different index procedures been chosen different results may have been seen. This being said the index procedures selected were chosen as they represent the vast majority of uro-oncological robotic surgical practice, largely mitigating for this shortfall.
Although the available ex vivo evidence suggests that introducing augmented reality operating environments into surgical practice would help to improve outcomes [9, 21] the in vivo experience to date is limited to small volume case series reporting feasibility [2, 3, 14]. To date no study has demonstrated an in vivo outcome advantage to augmented reality guidance. In addition to this limitation augmented reality has been demonstrated to increased rates of inattention blindness among surgeons suggesting there is a trade-off between increasing visual information and the surgeon’s ability to appreciate unexpected operative events [21].
Conclusions
This survey shows the contemporary robotic surgeon to be comfortable with the use of imaging to aid intra-operative planning; furthermore it highlights a significant interest among the urological community in augmented reality operating platforms.
Short- to medium-term development of augmented reality systems in robotic urology surgery would be best performed using RAPN as the index procedure. Not only was this the operation where surgeons saw the greatest potential benefits, but it may also be the operation where it is most easily achievable by capitalizing on the respective benefits of technologies the surgeons are already using; pre-operative CT for anatomical identification and intra-operative ultrasound for tumour resection.
Conflict of interest
None of the authors have any conflicts of interest to declare.
Appendix 1
| Question Asked |
Question Type |
| Demographics |
| In which country do you usually practise? |
Single best answer |
| Which robotic procedures do you perform?* |
Single best answer |
| Current Imaging Practice |
| What preoperative imaging modalities do you use for the staging and surgical planning in renal cancer? |
Multiple choice |
| How do you typically view preoperative imaging in theatre for renal cancer surgery? |
Multiple choice |
| Do you use intraoperative ultrasound for partial nephrectomy? |
Yes or No |
| What preoperative imaging modalities do you use for the staging and surgical planning in prostate cancer? |
Multiple choice |
| How do you typically view preoperative imaging in theatre for prostate cancer? |
Multiple choice |
| Do you use intraoperative ultrasound for robotic partial nephrectomy? |
Yes or No |
| Which preoperative imaging modality do you use for staging and surgical planning in muscle invasive TCC? |
Multiple choice |
| How do you typically view preoperative imaging in theatre for muscle invasive TCC? |
Multiple choice |
| Do you routinely refer to preoperative imaging intraoperativley? |
Yes or No |
| Do you routinely use Tilepro intraoperativley? |
Yes or No |
| Augmented Reality |
| Do you feel there is a role for augmented reality as a navigation tool in robotic surgery? |
Yes or No |
| Do you feel there is a role for augmented reality as a training tool in robotic surgery? |
Yes or No |
| In robotic partial nephrectomy which parts of the operation do you feel augmented reality image overlay technology would be of assistance? |
Multiple choice |
| In robotic nephrectomy which parts of the operation do you feel augmented reality image overlay technology would be of assistance? |
Multiple choice |
| In robotic prostatectomy which parts of the operation do you feel augmented reality image overlay technology would be of assistance? |
Multiple choice |
| Would augmented reality guidance be of use in lymph node dissection in robotic prostatectomy? |
Yes or No |
| In robotic cystectomy which parts of the operation do you feel augmented reality image overlay technology would be of assistance? |
Multiple choice |
| Would augmented reality guidance be of use in lymph node dissection in robotic cystectomy? |
Yes or No |
| *The relevant procedure related questions were displayed based on the answer to this question |
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