Henry Sun Sien Ho

Ultrasound Guided Robotic System for Transperineal Biopsy of the Prostate

We present a prototype of a robotic system for accurate and consistent insertion of a percutaneous biopsy needle into the prostate. The robot manipulates a transrectal ultrasound (TRUS) probe to collect a series of 2 dimensional (2D) images of the prostate, which are later used to create a 3D computer model of the organ. The urologist defines the needle’s entry point at the perineal wall and the biopsy points within the 3D model following a biopsy protocol or otherwise. The robotic system then calculates the required trajectory of the needle. The path of the needle going into the prostate can also be simulated with the 3D model before the actual insertion. Being satisfied with the predicted outcome, the urologist configures the robot accordingly and manually pushes the mechanically guided needle into the patient to take the biopsy. Cadaveric and human trials have validated the robot’s needle placement error to be less than 2.5mm. Our future work includes the integration of a cancer predictive modality into the system to increase the cancer detection rate. The robotic system could also be modified to accurately place foreign bodies into the prostate, which could improve therapeutic procedures such as Brachytherapy.

Robotic ultrasound-guided prostate intervention device: system description and results from phantom studies.

We introduce the first robotic ultrasound‐guided prostate intervention device and evaluate its safety, accuracy and repeatability.

Robotic transperineal prostate biopsy: pilot clinical study.

OBJECTIVE To develope a robot (BioXbot) that performs mapping transperineal prostate biopsy (PB) with two perineal skin punctures under ultrasound guidance. Our pilot studys clinical endpoints were complications and its technical endpoints were the duration for each phase. METHODS This institution review board-approved prospective clinical trial included patients with indications for PB. Two urologists performed these PBs. In the lithotomy position and under general anesthesia, the transrectal biplane ultrasound probe acquired transverse images of the prostate gland. The urologist defined its boundaries and planned the biopsy. It guided the PB in 3 axes, passing through a single perineal skin puncture for each prostate side. After each biopsy, it automatically moved to the next position. The steps were repeated on the contralateral side. RESULTS Our 20 patients had a mean prostate-specific antigen of 8.4 ± 4.9 ng/mL. Two patients had 2 previous biopsies, whereas the rest had one. The mean number of biopsies taken was 28.5 ± 6.2 in a mean total procedure time of 32.5 ± 3.2 minutes. We detected 3 patients with prostate cancer with Gleason score 3 + 3. Two patients required brief bladder catheterization after their biopsy. Their prostate volumes were >50 mL and the number of biopsies taken was >30 cores. There was no mechanical failure, sepsis, bleeding per-rectal, or perineal hematoma. CONCLUSION This pilot study demonstrated BioXbots safety and feasibility as a biopsy platform. It can potentially be used for image-guided PB and focal therapy.

Optimum slicing of radical prostatectomy specimens for correlation between histopathology and medical images.

PurposeThere is a need for methods which enable precise correlation of histologic sections with in vivo prostate images. Such methods would allow direct comparison between imaging features and functional or histopathological heterogeneity of tumors. Correlation would be particularly useful for validating the accuracy of imaging modalities, developing imaging techniques, assessing image-guided therapy, etc. An optimum prostate slicing method for accurate correlation between the histopathological and medical imaging planes in terms of section angle, thickness and level was sought.MethodsLiterature review (51 references from 1986–2009 were cited) was done on the various sectioning apparatus or techniques used to slice the prostate specimen for accurate correlation between histopathological data and medical imaging. Technology evaluation was performed with review and discussion of various methods used to section other organs and their possible applications for sectioning prostatectomy specimens.ResultsNo consensus has been achieved on how the prostate should be dissected to achieve a good correlation. Various customized sectioning instruments and techniques working with different mechanism are used in different research institutes to improve the correlation. Some of the methods have convincingly shown significant potential for improving image-specimen correlation. However, the semisolid consistent property of prostate tissue and the lack of identifiable landmarks remain challenges to be overcome, especially for fresh prostate sectioning and microtomy without external fiducials.ConclusionsA standardized optimum protocol to dissect prostatectomy specimens is needed for the validation of medical imaging modalities by histologic correlation. These standards can enhance disease management by improving the comparability between different modalities.

Evaluation on similarity measures of a surface-to-image registration technique for ultrasound images

Ultrasound is a universal guidance tool for many medical procedures, whereas it is of poor image quality and resolution. Merging high-contrast image information from other image modalities enhances the guidance capability of ultrasound. However, few registration methods work well for it. In this paper we present a surface-to-image registration technique for mono- or multimodal medical data concerning ultrasound. This approach is able to automatically register the object surface to its counterpart in image volume. Three similarity measurements are investigated in the rigid registration experiments of the pubic arch in transrectal ultrasound images. It shown that the selection of the similarity function is related to the ultrasound characteristics of the object to be registered.

ULTRASOUND GUIDED ROBOTIC BIOPSY OF THE PROSTATE

In this paper, a prototype of a robotic system for accurate and consistent insertion of a percutaneous biopsy needle into the prostate is presented. A transrectal ultrasound (TRUS) probe is used to collect a series of two-dimensional (2D) images of the prostate. These images are used to create a 3D computer model of the organ which is used by the urologist to define the biopsy points within the prostate. The robotic system then calculates the required trajectory of the needle, which can be simulated on the computer. Following this, the robot is configured accordingly and the actual biopsy is performed. Cadaveric and human trials have validated the robots needle placement error to be less than 2.5 mm. Our future work includes the integration of a cancer predictive modality into the system to increase the cancer detection rate. The robotic system could also be modified to accurately place foreign bodies into the prostate, which could improve therapeutic procedures such as Brachytherapy.

A 3D computer simulation to study the efficacy of transperineal versus transrectal biopsy of the prostate

Objectives This paper aims to provide an explanation for the positive findings of the improved prostate cancer detection rate by the transperineal approach when compared to the transrectal approach. The peripheral zone (PZ) is a region of the prostate with the most cancer occurrence. Hence, the ability to reach it consistently can improve the cancer detection rate significantly.Methods In a prospective study, ultrasound images taken from five patients were used to reconstruct the prostate, rectum and pubic bone with the perineal wall data obtained from the same patient. Each anatomical model virtually underwent prostate biopsy transperineally and transrectally with 10 cores biopsy each. We assessed the efficacy by calculating the volume of PZ tissue obtained from each approach.Results The overall volume of virtual core tissue taken from the PZ was 81.7% from a total volume of 100 prostate biopsy cores. Of the volume of tissue extracted transperineally, 98.5% was from the PZ compared to only 64.9% of the transrectally extracted tissue.Conclusions This is the first paper that acquires and reconstructs the virtual anatomy of the prostate, rectum and pubic bone with the perineal wall. Transperineal biopsy is superior to the transrectal method in obtaining the peripheral zone tissue. This explains the findings that the prostate cancer detection rate is higher via the transperineal approach.

Multiparametric MRI reporting using Prostate Imaging Reporting and Data System version 2 (PI-RADSv2) retains clinical efficacy in a predominantly post-biopsy patient population

Objective To evaluate the efficacy of multiparametric magnetic resonance imaging (mp-MRI) using Prostate Imaging Reporting and Data System version 2.0 (PI-RADSv2) definitions in detecting organ-confined prostate cancer. Methods All patients who underwent radical prostatectomy between January 1, 2014 and December 30, 2014 were identified. All underwent mp-MRI within 180 days before surgery. Those with prior pelvic irradiation or androgen deprivation therapy were excluded. Fully embedded, whole-mount histopathology was centrally reviewed and correlated with imaging for tumour location, Gleason score (GS) and stage. Results There were 39 patients included, of which 35 (90%) had mp-MRI done post-biopsy. A total of 93 cancer foci were identified on whole-mount pathology, of which mp-MRI detected 63 (68%). Of those detected by mp-MRI, 14 were PI-RADS 3 (n = 6 for GS 6, n = 8 for GS 7, no GS ≥ 8) and 49 were PI-RADS 4–5 (n = 7 for GS 6, n = 33 for GS 7, and n = 9 for GS ≥ 8). There were 30 (32%) cancer foci missed by mp-MRI (n = 15 for GS 6, n = 13 for GS 7 and n = 2 for GS ≥ 8). A lesion classified as PI-RADS 4–5 predicted a higher grade cancer on pathology as compared to PI-RADS 3 (for GS 7 lesions, odds ratio [OR] = 3.53, 95% CI: 0.93–13.45, p = 0.064). The mp-MRI size detection limit was 20 mm2 and 100 mm2 for 50% and 75% probability of cancer, respectively. In associating with radiological and pathologic stage, the weighted Kappa value was 0.69 (p < 0.0001). The sensitivity and positive predictive values for this study were 68% (95% CI: 57%–77%) and 78% (95% CI: 67%–86%), respectively. Conclusion In this predominantly post-biopsy cohort, mp-MRI using PI-RADSv2 reporting has a reasonably high diagnostic accuracy in detecting clinically significant prostate cancer.