Advantage of robotic needle placement on a prostate model in HDR brachytherapy.

Purpose: To compare the accuracy of the robot-assisted needle positioning with that of the conventional template-guided method with the help of a prostate model in high dose rate (HDR) brachytherapy.
Materials and Methods: A prostate model of fresh porcine abdomen and special polyvinylchloride (PVC) sheets was developed. To verify the model, deviations from 311 needle placements of real prostate implants were analyzed. Second, the accuracy of the template-guided positioning versus robot-assisted positioning was measured with 20 needle insertions in the model. For robot-assisted positioning, different velocities (2.7, 5.4, 9.8 mm/s) of needle insertion were investigated.
Results: The average needle positioning accuracies of manual template guidance on the model closely resembled those of real patients (approximately 3 mm). The average needle positioning accuracy for the robot-assisted method on the prostate model was 1.8 ± 0.6 mm, at a velocity of 2.7 mm/s and, in comparison to the template-guided method (2.7 ± 0.7 mm), was statistically more precise (p < 0.001). At higher robotic velocities, the measured needle positioning accuracy showed no significant difference from that of the manual insertion procedure.
Conclusion: By employing a prostate model, we showed for the first time that robot-assisted needle placement for HDR brachy-therapy is significantly more precise than the conventional method at a velocity of 2.7 mm/s. The robot-assisted needle positioning technique improves the degree of freedom by providing additional oblique insertion channels and could be potentially exploited not only for LDR but also for HDR brachytherapy.