The accuracy and safety aspects of a novel robotic needle guide manipulator to perform transrectal prostate biopsies

To introduce a new in-house developed pneumatically controlled magnetic field compatible manipulator as an aid to perform magnetic resonance (MR)-guided biopsies of the prostate.

A pneumatic controlled manipulator with five degrees of freedom constructed of plastic to achieve magnetic field compatibility was developed to guide biopsies. A risk analysis, mechanical tests, and RF safety tests with respect to needle tip heating were performed to assure future patient safety and to meet standard safety requirements for the use in a medical environment. The accuracy of needle positioning with the needle guide manipulator to sample a predefined target was measured in agar phantoms on a 3 T whole body MR system. The in-plane error was used to evaluate the accuracy, which is defined as the orthogonal distance between target and biopsy needle. The time for each step in the biopsy procedure was recorded to evaluate the procedure time. The influence of the insertion angle with respect to the static field of the MR scanner on the needle artifact was investigated.

The risk analyses met patient safety requirements. No RF induced local heating around the needle tip was observed. The average in-plane error in 19 measurements was 3.0 mm (range 0-5.6 mm). The average time needed for manipulation to place the needle guide in the desired position was 5 min (range 3-8 min). Total procedure time was 30 min. The needle artifact size increases with the insertion angle with respect to the static field of the MR scanner.

The new MR compatible manipulator can be used safely for patient care. It showed a high accuracy and short total procedure time, demonstrating great potential to improve the transrectal prostate biopsy procedure.