Needle release mechanism enabling multiple insertions with an ultrasound-guided prostate brachytherapy robot

We present a robotic system for transrectal ultrasound-guided prostate brachytherapy that employs a quick release mechanism to enable multiple needles to be inserted into the prostate prior to plan optimization. The mechanism consists of two actuated fingers that act as needle guides, thereby allowing insertion of both parallel and angled needles. Path planning, including reordering of needles within a batch, is required to avoid collisions with previously inserted needles. We perform two phantom experiments using clinical implant plans. The extra time required for the robotic motions, including finger actuation, is less than three minutes for the entire procedure. Mean position error is measured to be less than 0.5 mm, presumably due to the design of the needle guides, which have a toroidal shape to enable needle angulation.