Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia; St George Hospital Cancer Care Centre, Kogarah, NSW, Australia.
Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia.
Phys Med. 2019 Mar;59:30-36. doi: 10.1016/j.ejmp.2019.02.012. Epub 2019 Feb 26.
This study aims to assess the accuracy of in-vivo source tracking during real-time trans-rectal ultrasound (TRUS) based high dose rate (HDR) prostate brachytherapy (pBT) through Monte Carlo simulations of multiple HDR pBT treatments with a two-dimensional (2D) diode array, the Magic Plate 900 (MP900), embedded below the patient in a carbon-fibre couch.
Monte Carlo simulations of source positions representing three separate real-time TRUS based HDR pBT treatments were performed using the Geant4 toolkit. For each source position, an Ir-192 source was simulated inside a voxelized patient geometry. Dose deposited from each source position to the MP900 diodes was used to perform source tracking, and the MP900 calculated position compared to known source positions from the treatment plan. Thresholding techniques were implemented to improve source tracking accuracy with the TRUS probe present.
The average three-dimensional source position reconstruction discrepancy was 11.9 ± 2.4 mm and 1.5 ± 0.3 mm with and without the TRUS probe, respectively. Thresholding techniques improved the source position reconstruction discrepancy in the presence of the TRUS probe to 1.8 ± 0.4 mm.
Inclusion of the TRUS probe inside the patient negatively affects source tracking accuracy when using the MP900 diode array for HDR pBT verification. Modification of the source tracking algorithm using thresholding techniques improves source tracking in the presence of the TRUS probe, achieving similar accuracy as when the TRUS probe is not present. This study demonstrates that accurate in-vivo source tracking during real-time TRUS based HDR pBT is feasible using the Magic Plate system.
本研究旨在通过对二维（2D）二极管阵列 Magic Plate 900（MP900）在患者下方碳纤维治疗床上进行的多次高剂量率（HDR）前列腺近距离治疗（pBT）的蒙特卡罗模拟，评估实时经直肠超声（TRUS）引导下 HDR pBT 中体内源追踪的准确性。
使用 Geant4 工具包对代表三个独立实时 TRUS 引导 HDR pBT 治疗的源位置进行蒙特卡罗模拟。对于每个源位置，在体素化患者几何图形内部模拟 Ir-192 源。从每个源位置沉积到 MP900 二极管的剂量用于执行源追踪，并将 MP900 计算出的位置与治疗计划中的已知源位置进行比较。实施了阈值技术以提高 TRUS 探头存在时的源追踪准确性。
在没有和存在 TRUS 探头的情况下，平均三维源位置重建差异分别为 11.9±2.4mm 和 1.5±0.3mm。使用阈值技术可以改善 TRUS 探头存在时的源位置重建差异，达到 1.8±0.4mm。
当使用 MP900 二极管阵列进行 HDR pBT 验证时，将 TRUS 探头包含在患者内部会降低源追踪的准确性。使用阈值技术修改源追踪算法可以提高 TRUS 探头存在时的源追踪准确性，达到与 TRUS 探头不存在时相似的准确性。本研究表明，使用 Magic Plate 系统可以在实时 TRUS 引导 HDR pBT 过程中实现准确的体内源追踪。
