Critical evaluation of magnetic resonance imaging targeted, transrectal ultrasound guided transperineal fusion biopsy for detection of prostate cancer.

PURPOSE: Diagnosis and precise risk stratification of prostate cancer is essential for individualized treatment decisions. Magnetic resonance imaging/transrectal ultrasound fusion has shown encouraging results for detecting clinically significant prostate cancer. We critically evaluated magnetic resonance imaging targeted, transrectal ultrasound guided transperineal fusion biopsy in routine clinical practice. MATERIALS AND METHODS: Included in this prospective study were 347 consecutive patients with findings suspicious for prostate cancer. Median age was 65 years (range 42 to 84) and mean prostate specific antigen was 9.85 ng/ml (range 0.5 to 104). Of the men 49% previously underwent transrectal ultrasound guided biopsies, which were negative, and 51% underwent primary biopsy. In all patients 3 Tesla multiparametric magnetic resonance imaging was done. Systematic stereotactic prostate biopsies plus magnetic resonance imaging targeted, transrectal ultrasound guided biopsies were performed in those with abnormalities on magnetic resonance imaging. Imaging data and biopsy results were analyzed. A self-designed questionnaire was sent to all men on further clinical history and biopsy adverse effects. RESULTS: Of 347 patients biopsy samples of 200 (58%) showed prostate cancer and 73.5% of biopsy proven prostate cancer were clinically relevant according to National Comprehensive Cancer Network (NCCN) criteria. On multiparametric magnetic resonance imaging 104 men had findings highly suspicious for prostate cancer. The tumor detection rate was 82.6% (86 of 104 men) with a Gleason score of 7 or greater in 72%. Overall targeted cores detected significantly more cancer than systematic biopsies (30% vs 8.2%). Of 94 patients without cancer suspicious lesions on magnetic resonance imaging 11 (11.7%) were diagnosed with intermediate risk disease. Regarding adverse effects, 152 of 300 patients (50.6%) reported mild hematuria, 26% had temporary erectile dysfunction and 2.6% needed short-term catheterization after biopsy. Nonseptic febrile urinary tract infections developed in 3 patients (1%). CONCLUSIONS: Magnetic resonance imaging targeted, transrectal ultrasound guided transperineal fusion biopsy provides high detection of clinically significant tumors. Since multiparametric magnetic resonance imaging still has some limitations, systematic biopsies should currently not be omitted. The morbidity of the transperineal saturation approach is reasonable and mainly self-limiting.

Improving accuracy in image-guided prostate biopsy by using trocar-sharpened needles.

OBJECTIVE: To optimize image-guided prostate biopsy by minimizing the target error with trocar-sharpened needle tips instead of beveled needles, which constantly deviate away from the bevel. MATERIALS AND METHODS: We performed stereotactic biopsies on two prostate phantoms, which incorporate three randomly placed TRUS-visible lesions. Four stereotactic biopsies per lesion were taken under live-ultrasound guidance through a template: two biopsies with conventional beveled needles and two biopsies with novel trocar-sharpened needles. The procedural targeting error (PTE) between the virtually planned biopsy trajectory and the manually registered 3D needle position of every single biopsy core taken was calculated. RESULTS: The absolute overall targeting error using the novel needle-tip design was 0.13 mm (SD: ± 0.15 mm) with the highest PTE in the sagittal plane (0.18 ± 0.16 mm), followed by the coronal (0.13 ± 0.17 mm) and axial (0.09 ± 0.05 mm) planes. Comparing the PTE of the novel trocar-shaped needles with conventional beveled needles, there was a statistically significant difference in the axial plane [p (overall) = 0.47, p(axial) = 0.03]. CONCLUSION: The targeting error of stereotactic biopsies using trocar-sharpened needles is significantly lower than the targeting error of classical beveled needles. Thus, trocar-tip configurations improve the accuracy of computer-assisted biopsies and allow precise assessment of suspicious lesions in the prostate and in other organs accessible to image-guided biopsy.

A Platform and Multisided Market for Translational, Software-Defined Medical Procedures in the Operating Room (OP 4.1): Proof-of-Concept Study.

BACKGROUND: Although digital and data-based technologies are widespread in various industries in the context of Industry 4.0, the use of smart connected devices in health care is still in its infancy. Innovative solutions for the medical environment are affected by difficult access to medical device data and high barriers to market entry because of proprietary systems. OBJECTIVE: In the proof-of-concept project OP 4.1, we show the business viability of connecting and augmenting medical devices and data through software add-ons by giving companies a technical and commercial platform for the development, implementation, distribution, and billing of innovative software solutions. METHODS: The creation of a central platform prototype requires the collaboration of several independent market contenders, including medical users, software developers, medical device manufacturers, and platform providers. A dedicated consortium of clinical and scientific partners as well as industry partners was set up. RESULTS: We demonstrate the successful development of the prototype of a user-centric, open, and extensible platform for the intelligent support of processes starting with the operating room. By connecting heterogeneous data sources and medical devices from different manufacturers and making them accessible for software developers and medical users, the cloud-based platform OP 4.1 enables the augmentation of medical devices and procedures through software-based solutions. The platform also allows for the demand-oriented billing of apps and medical devices, thus permitting software-based solutions to fast-track their economic development and become commercially successful. CONCLUSIONS: The technology and business platform OP 4.1 creates a multisided market for the successful development, implementation, distribution, and billing of new software solutions in the operating room and in the health care sector in general. Consequently, software-based medical innovation can be translated into clinical routine quickly, efficiently, and cost-effectively, optimizing the treatment of patients through smartly assisted procedures.

A novel stereotactic prostate biopsy system integrating pre-interventional magnetic resonance imaging and live ultrasound fusion.

PURPOSE: We developed an effective way to precisely diagnose prostate cancer using a novel prostate biopsy system that integrates pre-interventional magnetic resonance imaging with peri-interventional ultrasound for perineal navigated prostate biopsy. MATERIALS AND METHODS: A total of 106 men with findings suspicious for prostate cancer (median age 66 years, prostate specific antigen 8.0 ng/ml and prostate volume 47 ml) underwent multiparametric 3 Tesla magnetic resonance imaging. Suspicious lesions were marked and data were transferred to the novel biopsy system. Using a custom-made biplane transrectal ultrasound probe mounted on a stepper we gathered 3-dimensional ultrasound data and fused them with magnetic resonance imaging data. As a result, suspicious magnetic resonance imaging lesions were superimposed over the transrectal ultrasound data. Three-dimensional biopsy planning was done, including systematic biopsies. Perineal biopsies were taken under live ultrasound guidance and the precise site of each biopsy was documented in 3 dimensions. We evaluated feasibility, safety and cancer detection. RESULTS: Prostate cancer was detected in 63 of 106 patients (59.4%). Magnetic resonance imaging findings correlated positively with histopathology in 71 of 103 patients (68.9%). In magnetic resonance imaging lesions marked as highly suspicious, the detection rate was 95.8% (23 of 24 cases). Lesion targeted cores had a significantly higher positivity rate than nontargeted cores. The procedural targeting error of the first 2,461 biopsy cores was 1.7 mm. Regarding adverse effects, 2 patients experienced urinary retention and 1 had a perineal hematoma. Urinary tract infections did not develop. CONCLUSIONS: Perineal stereotactic prostate biopsies guided by the combination of magnetic resonance imaging and ultrasound enable effective examination of suspicious magnetic resonance imaging lesions. Each biopsy core taken is documented accurately for its location in 3 dimensions, enabling magnetic resonance imaging validation and tailored treatment planning. The morbidity of the procedure was minimal.

Comparison of peripheral zone and central gland volume in patients undergoing intensity-modulated radiotherapy.

BACKGROUND AND PURPOSE: The shrinking effect of androgen deprivation therapy (ADT) and radiotherapy (RT) on prostate gland volume is a known clinical finding. Until now, it is not known which part of the prostate shrinks more. We examined patients with and without ADT undergoing intensity-modulated RT (IMRT) and performed 3-dimensional measurements of the peripheral zone (PZ) and central gland (CG) with magnetic resonance imaging (MRI). METHODS AND MATERIALS: Prostate gland volumes of PZ and CG between planning MRI and first available follow-up MRI were retrospectively determined in 44 patients with localized prostate carcinoma. A total of 24 patients had ADT with a median time interval of 5 months (range, 1.5-24 months). Median time interval between both MRI time points was 132 days (range, 104-224 days). Two observers performed PZ and CG delineation in consensus using planimetry. Volume changes over time were determined and compared. RESULTS: Patients who had ADT showed smaller prostate volume in the first MRI (mean [SD], 32 [16.7] mL), which was still present after IMRT (28.1 [16.7] mL). Patients who had no ADT started with 44.6 (16.9) mL and showed 37.5 (13.9) mL after IMRT. Shrinking effect in PZ was significantly larger than in CG for all patients (-18.3% vs -6.3%, P < 0.05). CONCLUSIONS: Because, typically, most tumors are located in PZ and this area also shows the largest shrinkage effect after IMRT, this should be taken into account for planning purposes. Notably, there are only minor differences in the relative shrinking effects between patients with and without ADT, although they start with different volumes.

Kidney edge detection in laparoscopic image data for computer-assisted surgery : Kidney edge detection.

PURPOSE: In robotic-assisted kidney surgery, computational methods make it possible to augment the surgical scene and potentially improve patient outcome. Most often, soft-tissue registration is a prerequisite for the visualization of tumors and vascular structures hidden beneath the surface. State-of-the-art volume-to-surface registration methods, however, are computationally demanding and require a sufficiently large target surface. To overcome this limitation, the first step toward registration is the extraction of the outer edge of the kidney. METHODS: To tackle this task, we propose a deep learning-based solution. Rather than working only on the raw laparoscopic images, the network is given depth information and distance fields to predict whether a pixel of the image belongs to an edge. We evaluate our method on expert-labeled in vivo data from the EndoVis sub-challenge 2017 Kidney Boundary Detection and define the current state of the art. RESULTS: By using a leave-one-out cross-validation, we report results for the most suitable network with a median precision-like, recall-like, and intersection over union (IOU) of 39.5 px, 143.3 px, and 0.3, respectively. CONCLUSION: We conclude that our approach succeeds in predicting the edges of the kidney, except in instances where high occlusion occurs, which explains the average decrease in the IOU score. All source code, reference data, models, and evaluation results are openly available for download: https://github.com/ghattab/kidney-edge-detection/.

High prevalence of DNA damage repair gene defects and TP53 alterations in men with treatment-naïve metastatic prostate cancer -Results from a prospective pilot study using a 37 gene panel.

BACKGROUND: Defects in DNA damage repair genes characterize a subset of men with prostate cancer and provide an attractive opportunity for precision oncology approaches. The prevalence of such perturbations in newly diagnosed, treatment-naïve patients with a high risk for lethal disease outcome, however, has not been sufficiently explored. PATIENTS AND METHODS: Prostate cancer specimens from 67 men with newly diagnosed early onset, localized high-risk/locally advanced or metastatic prostate cancer were included in this prospective pilot study. Tumor samples, including 30 prostate biopsies, were analyzed by targeted next generation sequencing using a formalin-fixed, paraffin-embedded tissue-optimized 37 DNA damage repair and checkpoint gene panel. RESULTS: The drop-out rate due to an insufficient quantity of DNA was 4.5% (3 of 67 patients). In the remaining 64 patients, the rate of pathogenic DNA damage repair gene mutations was 26.6%. The highest rate of pathogenic DNA damage repair and checkpoint gene mutations was found in men with treatment-naïve metastatic prostate cancer (38.9%). In addition, a high number of likely pathogenic mutations and gene deletions were detected. Altogether, one or more pathogenic mutation, likely pathogenic mutation or gene deletion affected 43 of 64 patients (67.2%) including 29 of 36 patients (80.6%) with treatment-naïve metastatic prostate cancer. Men with metastatic prostate cancer showed a high prevalence of alterations in TP53 (36.1%). CONCLUSIONS: This pilot study demonstrates the feasibility, performance and clinical relevance of somatic targeted next generation sequencing using a unique 37 DNA damage repair and checkpoint gene panel under routine conditions. Our results indicate that this approach can detect actionable DNA repair gene alterations, uncommon mutations as well as mutations associated with therapy resistance in a high number of patients, in particular patients with treatment-naïve metastatic prostate cancer.

PSMA-11-Derived Dual-Labeled PSMA Inhibitors for Preoperative PET Imaging and Precise Fluorescence-Guided Surgery of Prostate Cancer.

Resection of tumors using targeted dual-modality probes combining preoperative imaging with intraoperative guidance is of high clinical relevance and might considerably affect the outcome of prostate cancer therapy. This work aimed at the development of dual-labeled prostate-specific membrane antigen (PSMA) inhibitors derived from the established N,N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid (HBED-CC)-based PET tracer 68Ga-Glu-urea-Lys(Ahx)-HBED-CC (68Ga-PSMA-11) to allow accurate intraoperative detection of PSMA-positive tumors. Methods: A series of novel PSMA-targeting fluorescent dye conjugates of Glu-urea-Lys-HBED-CC was synthesized, and their biologic properties were determined in cell-based assays and confocal microscopy. As a preclinical proof of concept, specific tumor uptake, pharmacokinetics, and feasibility for intraoperative fluorescence guidance were investigated in tumor-bearing mice and healthy pigs. Results: The designed dual-labeled PSMA inhibitors exhibited high binding affinity and PSMA-specific effective internalization. Conjugation of fluorescein isothiocyanate (10.86 ± 0.94 percentage injected dose [%ID]/g), IRDye800CW (13.66 ± 3.73 %ID/g), and DyLight800 (15.62 ± 5.52 %ID/g) resulted in a significantly increased specific tumor uptake, whereas 68Ga-Glu-urea-Lys-HBED-CC-AlexaFluor488 (9.12 ± 5.47 %ID/g) revealed a tumor uptake similar to that of 68Ga-PSMA-11 (4.89 ± 1.34 %ID/g). The first proof-of-concept studies with the clinically relevant candidate 68Ga-Glu-urea-Lys-HBED-CC-IRDye800CW reinforced a fast, specific enrichment in PSMA-positive tumors, with rapid background clearance. With regard to intraoperative navigation, a specific fluorescence signal was detected in PSMA-expressing tissue. Conclusion: This study demonstrated that PSMA-11-derived dual-labeled dye conjugates are feasible for providing PSMA-specific pre-, intra-, and postoperative detection of prostate cancer lesions and have high potential for future clinical translation.

Correlation between genomic index lesions and mpMRI and 68Ga-PSMA-PET/CT imaging features in primary prostate cancer.

Magnetic resonance imaging (MRI) and prostate specific membrane antigen (PSMA)- positron emission tomography (PET)/computed tomography (CT)-imaging of prostate cancer (PCa) are emerging techniques to assess the presence of significant disease and tumor progression. It is not known, however, whether and to what extent lesions detected by these imaging techniques correlate with genomic features of PCa. The aim of this study was therefore to define a genomic index lesion based on chromosomal copy number alterations (CNAs) as marker for tumor aggressiveness in prostate biopsies in direct correlation to multiparametric (mp) MRI and 68Ga-PSMA-PET/CT imaging features. CNA profiles of 46 biopsies from five consecutive patients with clinically high-risk PCa were obtained from radiologically suspicious and unsuspicious areas. All patients underwent mpMRI, MRI/TRUS-fusion biopsy, 68Ga-PSMA-PET/CT and a radical prostatectomy. CNAs were directly correlated to imaging features and radiogenomic analyses were performed. Highly significant CNAs (≥10 Mbp) were found in 22 of 46 biopsies. Chromosome 8p, 13q and 5q losses were the most common findings. There was an strong correspondence between the radiologic and the genomic index lesions. The radiogenomic analyses suggest the feasibility of developing radiologic signatures that can distinguish between genomically more or less aggressive lesions. In conclusion, imaging features of mpMRI and 68Ga-PSMA-PET/CT can guide to the genomically most aggressive lesion of a PCa. Radiogenomics may help to better differentiate between indolent and aggressive PCa in the future.

Three-Dimensional Reconstruction of Preoperative Imaging Improves Surgical Success in Laparoscopy.

PURPOSE: To show the benefit of three-dimensional (3D) reconstructions of preoperative imaging for surgical performance. METHODS: A laparoscopic training environment with 15 hidden lymph nodes was designed. Three of them were marked with radiographic contrast agent and were only distinguishable from unmarked nodes via CT imaging. Thirty-six surgeons were divided into two groups. To group 1 the unprocessed CT data were shown. Group 2 was additionally shown a 3D reconstruction of the anatomy. Time of studying the imaging was recorded. All surgeons had to find the three target lymph nodes laparoscopically. Time to fulfill this task and errors was measured. Afterward, the 3D reconstruction was also shown to group 1. Then, all participants completed a questionnaire. Furthermore, 3D reconstructions were used in 15 clinical cases of partial nephrectomy or lymphadenectomy, and surgeons' opinion was evaluated with an additional questionnaire. The imaging and 3D reconstructions were available on a mobile device. RESULTS: The time of studying the imaging to gain confidence was significantly shorter with the 3D reconstruction. Laparoscopic intervention time was shortened and errors were reduced significantly within group 2. The clinical application of 3D reconstructions in difficult cases was believed to be helpful. CONCLUSIONS: 3D reconstructions of preoperative imaging lead to better surgical performance in a difficult laparoscopic training environment. Surgeons gain a 3D impression of patients' individual anatomy easier, faster, and more reliable. Providing 3D reconstructions previous to surgery should be routinely implemented for patients with complex anatomical situations.

Intraoperative Computed Tomography Imaging for Navigated Laparoscopic Renal Surgery: First Clinical Experience.

INTRODUCTION: Laparoscopic partial nephrectomy (LPN) remains challenging in endophytic and complex kidney tumors as the clear understanding of tumor location and spreading depends on a precise analysis of available imaging. The purpose of this study was to investigate navigated kidney surgery using intraoperative cone-beam computed tomography (CBCT) images in conjunction with a previously proposed method for augmented reality (AR) guidance for safe LPN. MATERIALS AND METHODS: The concept proposed is based on using an intraoperative CBCT scan for (1) marker-based AR guidance for fast and reliable tumor access and (2) enhancement of real-time fluoroscopy images for accurate tumor resection. Workflow and accuracy of the system were assessed using a porcine kidney model. Ten patients with complex or endophytic tumor localization and R.E.N.A.L. Nephrometry Score of at least nine scheduled for LPN were included in this study. Patients received an intraoperative CBCT after marker placement. Defining the resection line was assisted by AR. In addition, fluoroscopy imaging for depth perception was used for assistance during dissection. Feasibility and performance were assessed by histopathological results, peri- and postoperative data. RESULTS: Surgery was performed successfully and negative margins were found in all cases. Segmental branches of the renal artery shifted as much as 10 mm in the vertical and 11 mm in the sagittal axis intraoperatively compared to preoperative imaging. Fluoroscopy to intraoperative computed tomography image fusion enabled enhanced depth perception during dissection in all cases. Radiation dose area product was 4.8 mGym2. CONCLUSIONS: The application of the navigation system is feasible and allows for safe and direct access to complex or endophytic renal masses. Radiation limits the application to selected indications.

Robust augmented reality guidance with fluorescent markers in laparoscopic surgery.

PURPOSE: Laparoscopic interventions require the precise navigation of medical instruments through the patient's body, while taking critical structures into account. Although numerous concepts have been proposed for displaying subsurface anatomical detail using augmented reality, clinical translation of these methods has suffered from a lack of robustness as well as from cumbersome integration into the clinical workflow. The purpose of this study was to investigate the feasibility of a new approach to intra-operative registration based on fluorescent markers. METHODS: The proposed approach to augmented reality visualization relies on metabolizable fluorescent markers that are attached to the target organ to guide a 2D/3D intra-operative registration algorithm. In an ex vivo porcine study, marker tracking performance is evaluated in the presence of smoke, blood, and tissue in the field of view of the endoscope. RESULTS: In contrast to state-of-the-art needle-shaped fiducial markers, the fluorescent markers can be reliably tracked when occluded by smoke, blood or tissue. This makes the new 2D/3D intra-operative registration approach considerably more robust than state-of-the-art marker-based methods. CONCLUSION: As the concept can be smoothly integrated into the clinical workflow, its potential for application in clinical laparoscopy is high.

Trocar-sharpened needles for image-guided prostate biopsy improve sample quality and performance: first clinical results.

OBJECTIVE: To show the benefit of trocar-sharpened needles for image-guided prostate biopsy compared with standard bevelled needles in patients. MATERIALS AND METHODS: Twenty-four men underwent magnetic resonance imaging-targeted fusion-guided transperineal saturation prostate biopsy, each with half standard bevelled and half trocar-sharpened needles. All taken biopsies were scored (1=worse to 5=best) by one urologist for the following criteria. (1) Accuracy of matching between planned and performed biopsy. (2) Histologic quality of the sample. (3) Elegance, which is the easiness to take the biopsy in proper time, planned position, and best histologic quality. Afterward, the histologic sample quality was evaluated by a blinded pathologist. To show a possible training effect, blinded untrained junior residents performed biopsies in four men (103 cores). RESULTS: Overall, 600 single biopsies were analyzed. The trocar-sharpened needles demonstrated a significantly (p<0.05) better scoring for accuracy and elegance rated by the urologist. The histologic quality scored by the pathologist was superior. Moreover, significantly lower target errors with trocar-sharpened needles were achieved by untrained residents, but not by the experienced user. CONCLUSION: Using trocar-sharpened needles helps urologists to perform targeted prostate biopsy more elegantly and accurately. In addition, the histopathologic sample quality was superior, which may directly improve diagnostic certainty. There is an undeniable training effect in image-guided biopsy and unexperienced users can significantly reduce target errors with trocar-sharpened needles.

Augmented reality visualization during laparoscopic radical prostatectomy.

PURPOSE: We present an augmented reality (AR) navigation system that conveys virtual organ models generated from transrectal ultrasonography (TRUS) onto a real laparoscopic video during radical prostatectomy. By providing this additional information about the actual anatomy, we can support surgeons in their working decisions. This work reports the system's first in-vivo application. MATERIALS AND METHODS: The system uses custom-developed needles with colored heads that are inserted into the prostate as soon as the organ surface is uncovered. These navigation aids are once segmented in three-dimensional (3D) TRUS data that is acquired right after the placement of the needles and then continuously tracked in the laparoscopic video images by the surgical navigation system. The navigation system traces the navigation aids in real time and computes a registration between TRUS image and laparoscopic video based on the two-dimensional-three dimensional (2D-3D) point correspondences. With this registration, the system correctly superimposes TRUS-based 3D information on an additional AR monitor placed next to the normal laparoscopic screen. Surgical navigation guidance took place until the prostate was removed from the rectal wall. Finally, the navigation aids were removed together with the specimen inside the specimen bag. RESULTS: The initial human in-vivo application of the surgical navigation system was successful. No complications occurred, the prostate was removed together with the navigation aids, and the system supported the surgeons as intended with an AR visualization in real time. In case of tissue deformations, changes in the spatial configuration of the navigation aids are detected, which preserves the system from erroneous navigation visualization. CONCLUSIONS: Feasibility of the navigation system was shown in the first in-vivo application. TRUS information could be superimposed via AR in real time. To show the benefit for the patient, results obtained from a larger number of trials are needed.

In-vitro evaluation of a soft-tissue navigation system for laparoscopic prostatectomy.

PURPOSE: We introduce a custom-designed phantom model for the in-vitro evaluation of an augmented reality-based soft-tissue navigation system for ultrasound-guided prostate interventions. MATERIALS AND METHODS: Transrectal ultrasound segmentation of the prostate, navigation aid placement, initial registration, endoscope tracking, and enhanced visualization steps in the navigation procedure were performed to accommodate the actual prostatic motion. In-vitro laparoscopic manipulations simulating surgical procedures were performed by a physician using human prostate specimens. The target visualization error, defining the accuracy of the tracking, is determined by means of a leave-out test strategy by alternately using four navigation aids for endoscope registration and the remaining two navigation aids for accuracy verification. RESULTS: The introduction of the navigation aids lasted approximately 3 minutes. The navigation aids and especially their barbs were visible because of their ultrasound reflecting nature. For each organ, 1000 endoscope registrations were calculated, in which two randomly chosen navigation aids served the purpose of verifying the pose. We were able to demonstrate that the superimposed image could follow automatically the videoendoscopic real-time view. The mean target visualization errors for the respective trials were determined as 0.81 (±0.12) mm, 0.62 (±0.14) mm, and 0.98 (±0.23) mm. CONCLUSIONS: The ultrasound-based inside-out navigation system for laparoscopic prostatectomy overcomes the problem of tissue shift and deformation in an in-vitro model. In case of organ movement, the augmented picture with the detected navigation aids could follow the videoendoscopic image using the navigation aids as landmarks.

Augmented reality: a new tool to improve surgical accuracy during laparoscopic partial nephrectomy? Preliminary in vitro and in vivo results.

BACKGROUND: Use of an augmented reality (AR)-based soft tissue navigation system in urologic laparoscopic surgery is an evolving technique. OBJECTIVE: To evaluate a novel soft tissue navigation system developed to enhance the surgeon's perception and to provide decision-making guidance directly before initiation of kidney resection for laparoscopic partial nephrectomy (LPN). DESIGN, SETTING, AND PARTICIPANTS: Custom-designed navigation aids, a mobile C-arm capable of cone-beam imaging, and a standard personal computer were used. The feasibility and reproducibility of inside-out tracking principles were evaluated in a porcine model with an artificially created intraparenchymal tumor in vitro. The same algorithm was then incorporated into clinical practice during LPN. INTERVENTIONS: Evaluation of a fully automated inside-out tracking system was repeated in exactly the same way for 10 different porcine renal units. Additionally, 10 patients underwent retroperitoneal LPNs under manual AR guidance by one surgeon. MEASUREMENTS: The navigation errors and image-acquisition times were determined in vitro. The mean operative time, time to locate the tumor, and positive surgical margin were assessed in vivo. RESULTS AND LIMITATIONS: The system was able to navigate and superpose the virtually created images and real-time images with an error margin of only 0.5 mm, and fully automated initial image acquisition took 40 ms. The mean operative time was 165 min (range: 135-195 min), and mean time to locate the tumor was 20 min (range: 13-27 min). None of the cases required conversion to open surgery. Definitive histology revealed tumor-free margins in all 10 cases. CONCLUSIONS: This novel AR tracking system proved to be functional with a reasonable margin of error and image-to-image registration time. Mounting the pre- or intraoperative imaging properties on real-time videoendoscopic images in a real-time manner will simplify and increase the precision of laparoscopic procedures.