Title: MR-compatible transrectal prostate biopsy robot: a feasibility study

Introduction The recent symbiosis between robotics and medical science has made a rapid development, particularly in imaging and interventions. Different imaging modalities provide feedback to interventional devices which are crucial in precise positioning tasks such as needle insertion, biopsy interventions and catheter placement. Prostate cancer is the most frequently diagnosed form of noncutaneous cancer in men. Despite the low sensitivity and high specificity of transrectal ultrasound (TRUS)-guided biopsy for prostate cancer detection, TRUS-guided biopsy is still the standard procedure. Magnetic resonance (MR) imaging can be used as a diagnostic tool to detect, localize and stage prostate cancer. The detection rate is improved in patients with elevated prostate specific antigen and repetitive negative TRUS biopsies using MR-guided prostate biopsies [1]. So far, the only commercially available MR-guided prostate biopsy device is a manually adjustable standard for needle guide positioning. A needle guide filled with gadolinium is inserted in the rectum of the patient, based on the acquired MR images the needle guide is manually positioned in the direction of the region of interest . This procedure is unpleasant for the patient, operator-dependent, and time-consuming for the radiologist [2]. For these reasons an in-house pneumatic actuated MRcompatible robot is developed where needle guide direction can be controlled inside the controller room. Consequently the patient remains in the scanner bore. It is therefore conceivable that this robot may improve procedure time, enhances patient comfort and improve needle guide positioning. Thus, the purpose of our study was to establish proof of principle of a transrectal MRand robot-guided prostate biopsy using a phantom.