A Novel Integrated Mechanism With Dual RCM-Constraints Toward Robotic Transperineal Prostate Biopsy

Transperineal prostate biopsy (TPPB), a common procedure for clinically detecting prostate cancer, requires constant observation of the needle in the sagittal image plane of the transrectal ultrasound (TRUS) probe, shared needle puncture site and avoiding the obstruction of the pubic bone. In this article, we develop a novel TPPB robot with 9 DoFs that can place the needle guide and the TRUS probe to the desired position with dual integrated remote center of motion (RCM) constraints simultaneously before manual needle insertion. Based on a unique compact serial-parallel hybrid mechanism (dimensions of the core mechanism: 33 cm × 20 cm × 33 cm), the needle can access interest areas via two needle-RCM sites, and the probe moves with the probe-RCM constraint while keeping its sagittal plane coplanar with the needle. For the new mechanism, kinematic analysis is derived and full prostate coverage ability with dual RCM constraints is demonstrated. To demonstrate the RCM locations' programmability and system flexibility, a three-stage path-planning method considering avoiding obstacles is proposed. Experiments have shown that the trajectory tracking error with the probe-RCM is within 0.58$^{\circ }$ and 0.65 mm, and the needle-RCM accuracy remains within 0.69 mm. A phantom study validates the feasibility of the proposed system and its path-planning method.