Magnetic Resonance Imaging (MRI) has potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. The strong magnetic field prevents the use of conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intra-prostatic needle placement inside closed high-field MRI scanners. The robot performs needle insertion under real-time 3T MR image guidance; workspace requirements, MR compatibility, and workflow have been evaluated on phantoms. The paper explains the robot mechanism and controller design and presents results of preliminary evaluation of the system.

Prostate cancer biopsy is a routine medical procedure, yet conventional techniques suffer from low sensitivity attributed to suboptimal image guidance and needle placement. Targeting small lesions and foci (5 mm in diameter) is particularly prone to errors. We developed an integrated system to perform robot-assisted transperineal needle insertions into the prostate, under Magnetic Resonance Imaging (MRI) guidance. The system provides arbitrary needle trajectories and allows for simultaneous surveillance and correction of the needle path, based on intra-operative MRI. System functionality and data transfer and processing tests were conducted. Five lesions embedded in the gel phantom were targeted successfully, while communication delays (due to higher image frame rates) had no adverse affect on robot-software communication. The system was sufficiently resistant to high network loads and performed with an acceptable transfer rate.