A needle deflection model with operating condition optimization for corrective force-based needle guidance during transrectal prostate brachytherapy.

Abstract

Transrectal prostate brachytherapy (BT) involves the permanent implantation of radioactive seeds through a needle, which must be inserted along a straight path to satisfy dose distribution requirements. However, this process is complicated by bevelled needle tips that can cause deflection during penetration. In clinical practice, physicians typically rotate the bevelled tip intermittently or apply manual correction forces near the insertion point, to reduce needle deflection. While assisted rotational insertion robots have made substantial progress in the past 20 years, tissue sticking can be caused by rotation of the bevelled tip and there are currently few studies on the use of corrective forces. As such, an auxiliary needle insertion guide for transrectal prostate BT, based on corrective forces, is investigated in this study for the first time. The proposed BT guide is designed to reduce needle deflection and was experimentally verified by in vitro experiments. An energy-based deflection model was developed to predict needle motion as corrective forces were applied during insertion. An experimental platform was constructed to perform corrective force-assisted punctures, using the magnitude of the corrective force (A), the position of corrective force application (B) and the puncture speed (C) as test factors, with needle deflection as a test indicator. Design-Expert 8.0.5b software was used for simulation, and a high-definition camera acquired pictures of the needle tip as it pierced the tissue. A regression equation was also established for the test factors and test indicators, using Design-Expert software. Optimal parameter combinations (A, B and C) were determined through optimization. Calculated needle deflection values were then compared with the measured position of the needle insertion point, producing an average error of 0.39 ± 0.28 mm. Deflection was as low as 0.8 mm using optimal puncture parameters CONCLUSIONS: A needle-tissue interaction model, considering tissue nonlinearity, which experimental results demonstrated to be highly accurate. Optimal puncture parameters effectively improved puncture accuracy.