Département de physique, de génie physique et d'optique, et Centre de recherche sur le cancer, Université Laval, Québec, Québec, Canada.
Service de physique médicale et de radioprotection, Centre intégré de cancérologie, CHU de Québec-Université Laval et Centre de recherche du CHU de Québec, Québec, Québec, Canada.
Med Phys. 2022 Oct;49(10):6575-6587. doi: 10.1002/mp.15878. Epub 2022 Aug 8.
Currently, in high-dose rate (HDR) brachytherapy planning, the catheter's positions are often selected by the planner, which involves the planner's experience. The catheters are then inserted using a template that helps to guide the catheters. For certain applications, it is of interest to choose the optimal location and number of catheters needed for dose coverage and potential decrease of the treatment's toxicity. Hence, it is of great importance to develop patient-specific algorithms for catheters and dose optimization.
A modified Centroidal Voronoi tessellation (CVT) algorithm is implemented and merged with a graphics processing unit (GPU)-based multi-criteria optimization algorithm (gMCO). The CVT algorithm optimizes the catheters' positions, and the gMCO algorithm optimizes the dwell times and dwell positions. The CVT algorithm can be used simultaneously for insertion with or without a template. Some improvements to the CVT algorithm are presented such as a new way of considering the area that needs to be covered. One hundred eight previously treated prostates HDR cases using real-time ultrasound are used to evaluate the different optimization procedures. The plan robustness is evaluated using two types of errors: deviations (random) in the insertion and deviation (systematic) in the reconstruction of the catheters.
Using gMCO on clinically inserted catheter increases the acceptance rate by 37% for Radiation Therapy Oncology Group (RTOG) criteria. Our results show that all the patients respect RTOG criteria with 11 catheters using CVT+gMCO with a template of 5 mm. The number of catheters needed for all patients to respect RTOG criteria with the freehand technique is 10 catheters using CVT+gMCO. When deviations are introduced, using a template, the acceptance rate goes to 85% with 3 mm deviations using 11 catheters. This decrease is less significant when the number of catheters is higher, decreasing by less than 5% with a 3 mm deviation using 13 catheters or more. In conclusion, it is feasible to decrease the number of catheters needed to treat most patients.
Some cases still need a high number of catheters to reach the plan's criteria. Using gMCO allows an increase in the plan quality, while using CVT reduces the number of catheters. A higher number of catheters equates to plans that are more robust to deviations.
目前，在高剂量率（HDR）近距离放射治疗计划中，导管的位置通常由规划师选择，这涉及到规划师的经验。然后使用模板插入导管，以帮助引导导管。对于某些应用，选择覆盖剂量和降低治疗毒性所需的最佳导管位置和数量是很有意义的。因此，开发针对患者的导管和剂量优化算法非常重要。
实现了一种改进的质心 Voronoi 细分（CVT）算法，并将其与基于图形处理单元（GPU）的多准则优化算法（gMCO）合并。CVT 算法优化导管的位置，gMCO 算法优化驻留时间和驻留点。CVT 算法可同时用于有或没有模板的插入。本文提出了一些 CVT 算法的改进，例如一种新的考虑需要覆盖的区域的方法。使用实时超声对 108 例先前接受 HDR 治疗的前列腺癌患者进行了评估，以评估不同的优化过程。使用两种类型的误差来评估计划的稳健性：插入中的偏差（随机）和导管重建中的偏差（系统）。
在临床插入的导管上使用 gMCO 可将放射治疗肿瘤学组（RTOG）标准的接受率提高 37%。我们的结果表明，使用模板的 CVT+gMCO 可使所有患者均符合 RTOG 标准，使用 11 根导管。使用徒手技术，所有患者均符合 RTOG 标准所需的导管数量为 10 根，使用 CVT+gMCO。当引入偏差时，使用模板时，使用 3mm 偏差和 11 根导管的接受率为 85%。当导管数量较高时，这种下降不那么显著，使用 13 根或更多导管，3mm 偏差时下降小于 5%。总之，减少大多数患者所需的导管数量是可行的。
有些病例仍需要大量的导管来达到计划标准。使用 gMCO 可以提高计划质量，而使用 CVT 可以减少导管数量。导管数量越多，计划对偏差的鲁棒性就越高。
