Robotic assistance for ultrasound guided prostate brachytherapy.

We present a robotically assisted prostate brachytherapy system and test results in training phantoms. The system consists of a transrectal ultrasound (TRUS) and a spatially co-registered robot integrated with an FDA-approved commercial treatment planning system. The salient feature of the system is a small parallel robot affixed to the mounting posts of the template. The robot replaces the template interchangeably and uses the same coordinate system. Established clinical hardware, workflow and calibration are left intact. In these experiments, we recorded the first insertion attempt without adjustment. All clinically relevant locations were reached. Non-parallel needle trajectories were achieved. The pre-insertion transverse and rotational errors (measured with Polaris optical tracker relative to the template's coordinate frame) were 0.25mm (STD = 0.17mm) and 0.75 degrees (STD = 0.37 degrees). The needle tip placement errors measured in TRUS were 1.04mm (STD = 0.50mm). The system is in Phase-I clinical feasibility and safety trials, under Institutional Review Board approval.