A robotic needle guide for prostate brachytherapy

Low dose rate prostate brachytherapy involves the permanent implant of radioactive sources into the prostate region using needles. We present a four-degree-of-freedom robot for prostate brachytherapy. The robot can translate a needle guide in the X-Y plane allowing for precise needle insertion along the Z direction. It can also rotate the guide about the X and Y axes, providing thus fine control over the needle insertion point and angle. The robot is light and mountable on a standard brachytherapy stepper. It is non- back-drivable providing a stable needle insertion direction when the power is off. It allows for manual control of each of the motor axes for fine positioning and has a quick-release mechanism for gross translation of the needle guide. We present the robot design and the performance characteristics of the prototype we built. The robot has an interface that allows the guide to be stepped through a complete treatment plan. A radiation oncologist implanted a phantom according to a treatment plan. Only 32 minutes were required for the complete implant that had 26 needles with 136 seeds. This demonstrates that, in spite of its increased flexibility of use, the robotic guide does not add to the procedure time.