Poder Joel, Whitaker May
Radiation Oncology, Chris O'Brien Lifehouse, Camperdown, NSW; Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
Radiation Oncology, Chris O'Brien Lifehouse, Camperdown, NSW.
J Contemp Brachytherapy. 2016 Jun;8(3):201-7. doi: 10.5114/jcb.2016.60499. Epub 2016 Jun 13.
Inverse planning simulated annealing (IPSA) optimized brachytherapy treatment plans are characterized with large isolated dwell times at the first or last dwell position of each catheter. The potential of catheter shifts relative to the target and organs at risk in these plans may lead to a more significant change in delivered dose to the volumes of interest relative to plans with more uniform dwell times.
This study aims to determine if the Nucletron Oncentra dwell time deviation constraint (DTDC) parameter can be optimized to improve the robustness of high-dose-rate (HDR) prostate brachytherapy plans to catheter displacements. A set of 10 clinically acceptable prostate plans were re-optimized with a DTDC parameter of 0 and 0.4. For each plan, catheter displacements of 3, 7, and 14 mm were retrospectively applied and the change in dose volume histogram (DVH) indices and conformity indices analyzed.
The robustness of clinically acceptable prostate plans to catheter displacements in the caudal direction was found to be dependent on the DTDC parameter. A DTDC value of 0 improves the robustness of planning target volume (PTV) coverage to catheter displacements, whereas a DTDC value of 0.4 improves the robustness of the plans to changes in hotspots.
The results indicate that if used in conjunction with a pre-treatment catheter displacement correction protocol and a tolerance of 3 mm, a DTDC value of 0.4 may produce clinically superior plans. However, the effect of the DTDC parameter in plan robustness was not observed to be as strong as initially suspected.
逆向计划模拟退火（IPSA）优化的近距离放射治疗计划的特点是在每个导管的第一个或最后一个驻留位置有较大的孤立驻留时间。在这些计划中，导管相对于靶区和危及器官发生移位的可能性，可能导致与驻留时间更均匀的计划相比，感兴趣体积的剂量输送变化更大。
本研究旨在确定能否优化核通公司Oncentra驻留时间偏差约束（DTDC）参数，以提高高剂量率（HDR）前列腺近距离放射治疗计划对导管移位的稳健性。一组10个临床可接受的前列腺计划分别使用DTDC参数0和0.4进行重新优化。对于每个计划，回顾性应用3、7和14毫米的导管移位，并分析剂量体积直方图（DVH）指数和适形指数的变化。
发现临床可接受的前列腺计划对导管尾端方向移位的稳健性取决于DTDC参数。DTDC值为0可提高计划靶区（PTV）覆盖对导管移位的稳健性，而DTDC值为0.4可提高计划对热点变化的稳健性。
结果表明，如果与治疗前导管移位校正方案以及3毫米的容差结合使用，DTDC值0.4可能产生临床上更优的计划。然而，未观察到DTDC参数对计划稳健性的影响如最初怀疑的那么强烈。
