Robotic needle guide for prostate brachytherapy: clinical testing of feasibility and performance

Optimization of prostate brachytherapy is constrained by tissue deflection of needles and fixed spacing of template holes. We developed and clinically tested a robotic guide toward the goal of allowing greater freedom of needle placement.

The robot consists of a small tubular needle guide attached to a robotically controlled arm. The apparatus is mounted and calibrated to operate in the same coordinate frame as a standard template. Translation in x and y directions over the perineum ±40 mm are possible. Needle insertion is performed manually.

Five patients were treated in an institutional review board-approved study. Confirmatory measurements of robotic movements for initial 3 patients using infrared tracking showed mean error of 0.489 mm (standard deviation, 0.328 mm). Fine adjustments in needle positioning were possible when tissue deflection was encountered; adjustments were performed in 54 (30.2%) of 179 needles placed, with 36 (20.1%) of 179 adjustments of >2mm. Twenty-seven insertions were intentionally altered to positions between the standard template grid to improve the dosimetric plan or avoid structures such as pubic bone and blood vessels.

Robotic needle positioning provided a means of compensating for needle deflections and the ability to intentionally place needles into areas between the standard template holes. To our knowledge, these results represent the first clinical testing of such a system. Future work will be incorporation of direct control of the robot by the physician, adding software algorithms to help avoid robot collisions with the ultrasound, and testing the angulation capability in the clinical setting.