MRI-safe robot for targeted transrectal prostate biopsy: animal experiments.

OBJECTIVES To study the feasibility and safety of using a magnetic resonance imaging (MRI)-safe robot for assisting MRI-guided transrectal needle placement and biopsy in the prostate, using a canine model. To determine the accuracy and precision afforded by the use of the robot while targeting a desired location in the organ. MATERIALS AND METHODS In a study approved by the Institutional Animal Care and Use Committee, six healthy adult male beagles with prostates of at least 15 × 15 mm in size at the largest transverse section were chosen for the procedure. The probe portion of the robot was placed into the rectum of the dog, images were acquired and image-to-robot registration was performed. Images acquired after placement of the robot were reviewed and a radiologist selected targets for needle placement in the gland. Depending on the size of the prostate, up to a maximum of six needle placements were performed on each dog. After needle placement, robot-assisted core biopsies were performed on four dogs that had larger prostate volumes and extracted cores were analysed for potential diagnostic value. RESULTS Robot-assisted MRI-guided needle placements were performed to target a total of 30 locations in six dogs, achieving a targeting accuracy of 2.58 mm (mean) and precision of 1.31 mm (SD). All needle placements were successfully completed on the first attempt. The mean time required to select a desired target location in the prostate, align the needle guide to that point, insert the needle and perform the biopsy was ∼ 3 min. For this targeting accuracy study, the inserted needle was also imaged after its placement in the prostate, which took an additional 6-8 min. Signal-to-noise ratio analysis indicated that the presence of the robot within the scanner bore had minimal impact on the quality of the images acquired. Analysis of intact biopsy core samples indicated that the samples contained prostatic tissues, appropriate for making a potential diagnosis. Dogs used in the study did not experience device- or procedure-related complications. CONCLUSIONS Results from this preclinical pilot animal study suggest that MRI-targeted transrectal biopsies are feasible to perform and this procedure may be safely assisted by an MRI-safe robotic device.