Design evaluation of a double ring RCM mechanism for robotic needle guidance in MRI-guided liver interventions

MRI-guided percutaneous liver interventions have been investigated by researchers as an alternative to CT-guided procedures as it is non-invasive and provides greater soft tissue details. In practice, however, repeated needle insertion is still required to reach desired positions on trial-and-error basis. To minimize the needle attempt and procedural time, we designed a robotic needle guidance device that provides needle insertion angle guidance at skin entry using two rotational joints structured for remote-center-of-motion manipulation. To evaluate the mechanism and clinical feasibility, we fabricated a proof-of-concept prototype that can be manually operated. As preliminary design evaluation, we conducted a retrospective clinical study of 13 MRI-guided abdominal biopsies to determine if the proposed mechanism and device can provide necessary needle insertion angles in MRI-guided liver biopsy procedures. The number of needle insertion attempts per biopsy was also measured. To confirm the kinematic design of the double ring remote-center-of-motion mechanism and to identify any procedural difficulties, we conducted a phantom targeting experiment. The retrospective clinical study showed that the 80 degree insertion angle coverage of the device is sufficient for clinical cases, and an average of five needle insertion attempts per biopsy in conventional MRI-guided biopsy can be reduced by the proposed device. A phantom targeting experiment confirmed that the unique kinematic design was successfully implementation in the targeting.