Toward Image Guided Robotic Surgery: System Validation

In robot-assisted partial nephrectomy, kidney tumors are removed surgically, along with a margin of healthy tissue around the tumor. This margin is taken to prevent positive margins (i.e. tumor tissue accidentally left behind). Yet it is desirable to minimize the thickness of the margin, since the effectiveness of post-surgery kidney function is related to the volume of kidney tissue preserved. In this paper we use statistical information on robot-mediated surface-based registration to select variable-thickness margins that optimally account for registration uncertainty. These margins can then be displayed in the surgeon console to provide enhanced information to the surgeon during robotic partial nephrectomy.

Since FDA approval of the da Vinci system for general laparoscopic surgery in 2000, application of robotic surgery has been spread rapidly to include gynecological laparoscopic surgical procedures worldwide. In Japan, da Vinci S system was first approved in 2009 for urology, gynecology, general surgery, and thoracic surgery. However, mostly due to lack of cost coverage by public health insurance in Japan, robotic surgery is not popular in gynecologic field. Meantime, in the USA and some other European countries, robotic surgery has been shown to be superior to laparotomy and even to laparoscopy and has already become a standard in uterine cervix and endometrial cancer surgery. Robotic surgery is basically defined as “computer-mediated surgery,” which enables it to integrate various computer-based technologies, such as remote surgery, image-guided surgery, and surgical education in future, leading to a drastic change in the field of surgery. Healthy development of robotic surgery in Japan is an urgent issue.

Video Imaging and Documentation

For a variety of head and neck cancers, specifically those of the oropharynx, larynx, and hypopharynx, minimally invasive trans-oral approaches have been developed to reduce perioperative and long-term morbidity. However, in trans-oral surgical approaches anatomical deformation due to instrumentation, specifically placement of laryngoscopes and retractors, present a significant challenge for surgeons relying on preoperative imaging to resect tumors to negative margins. Quantifying the deformation due to instrumentation is needed in order to develop predictive models of operative deformation. In order to study this deformation, we used a CT/MR-compatible laryngoscopy system in concert with intraoperative CT imaging. 3D models of preoperative and intraoperative anatomy were generated. Mandible and hyoid displacements as well as tongue deformations were quantified for eight patients undergoing diagnostic laryngoscopy. Across patients, we found on average 1.3cm of displacement for these anatomic structures due to laryngoscope insertion. On average, the maximum displacement for certain tongue regions exceeded 4cm. The anatomical deformations quantified here can serve as a reference for describing how the upper aerodigestive tract anatomy changes during instrumentation and may be helpful in developing predictive models of intraoperative upper aerodigestive tract deformation.

Purpose: To develop image processing algorithms for noninvasive mapping of microwave thermal ablation using X-ray CT.Methods: Ten specimens of bovine liver were subjected to microwave ablation (20–80 W, 8 min) while scanned by X-ray CT at 5 s intervals. Specimens were cut and manually traced by two observers. Two algorithms were developed and implemented to map the ablation zone. The first algorithm utilises images segmentation of Hounsfield units changes (ISHU). The second algorithm utilises radial optical flow (ROF). Algorithm sensitivity to spatiotemporal under-sampling was assessed by decreasing the acquisition rate and reducing the number of acquired projections used for image reconstruction in order to evaluate the feasibility of implementing radiation reduction techniques.Results: The average radial discrepancy between the ISHU and ROF contours and the manual tracing were 1.04±0.74 and 1.16±0.79mm, respectively. When diluting the input data, the ISHU algorithm retained its accuracy, ranging from 1.04 to 1.79mm. By contrast, the ROF algorithm performance became inconsistent at low acquisition rates. Both algorithms were not sensitive to projections reduction, (ISHU: 1.24±0.83mm, ROF: 1.53±1.15mm, for reduction by eight fold). Ablations near large blood vessels affected the ROF algorithm performance (1.83±1.30mm; p < 0.01), whereas ISHU performance remained the same.Conclusion: The two suggested noninvasive ablation mapping algorithms can provide highly accurate contouring of the ablation zone at low scan rates. The ISHU algorithm may be more suitable for clinical practice as it appears more robust when radiation dose reduction strategies are employed and when the ablation zone is near large blood vessels.

In transoral robotic surgery preoperative image data do not reflect large deformations of the operative workspace from perioperative setup. To address this challenge, in this study we explore image guidance with cone beam computed tomographic angiography to guide the dissection of critical vascular landmarks and resection of base-of-tongue neoplasms with adequate margins for transoral robotic surgery. We identify critical vascular landmarks from perioperative c-arm imaging to augment the stereoscopic view of a da Vinci si robot in addition to incorporating visual feedback from relative tool positions. Experiments resecting base-of-tongue mock tumors were conducted on a series of ex vivo and in vivo animal models comparing the proposed workflow for video augmentation to standard non-augmented practice and alternative, fluoroscopy-based image guidance. Accurate identification of registered augmented critical anatomy during controlled arterial dissection and en bloc mock tumor resection was possible with the augmented reality system. The proposed image-guided robotic system also achieved improved resection ratios of mock tumor margins (1.00) when compared to control scenarios (0.0) and alternative methods of image guidance (0.58). The experimental results show the feasibility of the proposed workflow and advantages of cone beam computed tomography image guidance through video augmentation of the primary stereo endoscopy as compared to control and alternative navigation methods.

Central to any image-guided surgical procedure is the alignment of image and physical coordinate spaces, or registration. We explored the task of registration in the kidney through in vivo and ex vivo porcine animal models and a human study of minimally invasive kidney surgery. A set of (n = 6) ex vivo porcine kidney models was utilized to study the effect of perfusion and loss of turgor caused by incision. Computed tomography (CT) and laser range scanner localizations of the porcine kidneys were performed before and after renal vessel clamping and after capsular incision. The da Vinci robotic surgery system was used for kidney surface acquisition and registration during robot-assisted laparoscopic partial nephrectomy. The surgeon acquired the physical surface data points with a tracked robotic instrument. These data points were aligned to preoperative CT for surface-based registrations. In addition, two biomechanical elastic computer models (isotropic and anisotropic) were constructed to simulate deformations in one of the kidneys to assess predictive capabilities. The mean displacement at the surface fiducials (glass beads) in six porcine kidneys was 4.4 ± 2.1 mm (range 3.4-6.7 mm), with a maximum displacement range of 6.1 to 11.2 mm. Surface-based registrations using the da Vinci robotic instrument in robot-assisted laparoscopic partial nephrectomy yielded mean and standard deviation closest point distances of 1.4 and 1.1 mm. With respect to computer model predictive capability, the target registration error was on average 6.7 mm without using the model and 3.2 mm with using the model. The maximum target error reduced from 11.4 to 6.2 mm. The anisotropic biomechanical model yielded better performance but was not statistically better. An initial point-based alignment followed by an iterative closest point registration is a feasible method of registering preoperative image (CT) space to intraoperative physical (robot) space. Although rigid registration provides utility for image-guidance, local deformations in regions of resection may be more significant. Computer models may be useful for prediction of such deformations, but more investigation is needed to establish the necessity of such compensation.

The broad range of Computer Assisted Surgery (CAS) represents the integration of computer technology in surgical procedures for presurgical planning, guiding or manipulation. Surgical robots and surgical endoscopic navigation are the most challenging applications to urology. A surgical robot is defined as a computer-controlled manipulator with artificial sensing which can be programmed to move, and position tools to carry out surgical tasks. In urology, robots have been tested in two areas: endourology and laparoscopy. Surgical navigation allows the surgeon to process data from pre- and intraoperative sources, aiming at purification and presentation of the most relevant information. Image-guided systems (IGS), augmented reality (AR) and navigation in endoscopic soft tissue surgery represent the three main topics of surgical urological navigation. IGS involve matching the coordinates from medical imaging (preoperative registration) with coordinates from the patient in the operating room (registration and updating images). IGS have become the standard of care in providing navigational assistance during neurosurgery, offering subsurface and functional information to the surgeon.

Objective: Kanazawa University introduced the da Vinci surgical system and the Radius surgical system. In this study, we compared the advantages and disadvantages of each system. Methods: The da Vinci system is a master-slave tele-manipulation system, which provides hi-resolution 3D images. The Radius system is pair of hand-guided surgical manipulators. In this study we focus on the operability of both instruments rather than their 3D optical systems. Results: The Radius was originally developed specifically focused on ligation and suturing with suture sizes bigger than 4-0, it is more effective, less expensive compared with the da Vinci. Although the da Vinci system is bulky, it allows surgeons to perform endoscopic surgeries only if ports are properly placed to prevent each arm from colliding with the other arms. A crucial difference between the Radius and the da Vinci is not limited to anastomose small vessels but is extended to multidirectional dissection. Currently, the cost including initial investment is the biggest issue; however, the da Vinci is absolutely necessary to implement delicate cardiac surgeries endoscopically and less-invasively. Early approval of robotic surgery by the government is urgently required in Japan. Conclusions: Although both the da Vinci and the Radius have endoscopic instruments with a multi-degree of freedom, applications need to be differentiated depending on the procedures and indications. Therefore, it can be clearly said that these unique innovative systems will never compete against each other.

Augmented Reality Partial Nephrectomy: Examining the Current Status and Future Perspectives