Wang Lin, Zhang Jianping, Huang Miaoyun, Xu Benhua, Li Xiaobo
Department of Radiation Oncology, Fujian Medical University Union Hospital, Fuzhou, China.
Department of Medical Imaging Technology, College of Medical Technology and Engineering, Fujian Medical University, Fuzhou, China.
Dose Response. 2022 Jul 8;20(3):15593258221105678. doi: 10.1177/15593258221105678. eCollection 2022 Jul-Sep.
The present study aimed to investigate the dose differences and radiobiological assessment between Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB) with its 2 calculation models, namely, dose-to-water (AXB-Dw) and dose-to-medium (AXB-Dm), on esophageal carcinoma radiotherapy treatment plans.
The AXB-Dw and AXB-Dm plans were generated by recalculating the initial 66 AAA plans using the AXB algorithm with the same monitor units and beam parameters as those in the original plan. The dosimetric and radiobiological assessment parameters were calculated for the planning target volume (PTV) and organs at risk (OARs). The gamma agreement for the PTV and the correlation between it and the volume of the air cavity and bone among the different algorithms were compared simultaneously. The dose discrepancy between the theoretical calculation and treatment planning system (TPS) when switching from AXB-Dm to AXB-Dw was analyzed according to the composition of the structures.
The PTV dose of AXB-Dm plans was significantly smaller than that of the AAA and AXB-Dw plans (P < .05), except for D. The difference values for AAA vs AXB-Dm (∆ ) and AXB-Dw vs AXB-Dm (∆ ) were 1.94% [1.27%, 2.64%] and 1.95% [1.56%, 2.27%], respectively. For the spinal cord and heart, there were obvious differences between the AAA vs AXB-Dm (spinal cord: 1.15%, heart: 2.89%) and AXB-Dw vs AXB-Dm (spinal cord: 1.88%, heart: 3.25%) plans. For the lung, the differences between AAA vs AXB-Dm and AAA vs AXB-Dw were significantly larger than those of AXB-Dm vs AXB-Dw. Compared to the case of AAA and AXB-Dw, the decrease in biologically effective dose (BED, ) of AXB-Dm due to dose non-uniformity exceeded 6.5%, even for a small . The average values of equivalent uniform dose in the AAA, AXB-Dw, and AXB-Dm plans were 52.03±.39 Gy, 52.24 ± .81 Gy, and 51.13 ± .47 Gy, respectively. The tumor control probability (TCP) results for PTV in the AAA, AXB-Dw, and AXB-Dm plans were 62.29 ± 1.57%, 62.82 ± 1.69%, and 58.68±1.88%, respectively. With the 2%/2 mm and 3%/3 mm acceptance criteria, the mean values of , , and were 87.24, 63.3, and 64.81% vs 97.86, 91.77, and 89.25%, respectively. The dose discrepancy between the theoretical calculation and TPS when switching from AXB-Dm to AXB-Dw was approximately 1.63%.
The AAA and AXB-Dw algorithms overestimated the radiobiological parameters when the tumor particularly consisted of nonuniform tissues. A relatively small dose difference could cause a significant reduction in the corresponding TCP. Dose distribution algorithms should be carefully chosen by physicists and oncologists to improve tumor control, as well as to optimize OARs protection.
本研究旨在探讨在食管癌放射治疗计划中，各向异性分析算法（AAA）与Acuros外照射（AXB）及其两种计算模型（即水剂量计算模型（AXB-Dw）和介质剂量计算模型（AXB-Dm））之间的剂量差异和放射生物学评估。
使用AXB算法重新计算最初的66个AAA计划，生成AXB-Dw和AXB-Dm计划，保持与原始计划相同的监测单位和射束参数。计算计划靶区（PTV）和危及器官（OARs）的剂量学和放射生物学评估参数。同时比较PTV的γ通过率及其与不同算法中气腔和骨骼体积之间的相关性。根据结构组成分析从AXB-Dm切换到AXB-Dw时理论计算与治疗计划系统（TPS）之间的剂量差异。
除D外，AXB-Dm计划的PTV剂量显著低于AAA和AXB-Dw计划（P <.05）。AAA与AXB-Dm（∆）以及AXB-Dw与AXB-Dm（∆）的差值分别为1.94% [1.27%，2.64%]和1.95% [1.56%，2.27%]。对于脊髓和心脏，AAA与AXB-Dm（脊髓：1.15%，心脏：2.89%）以及AXB-Dw与AXB-Dm（脊髓：1.88%，心脏：3.25%）计划之间存在明显差异。对于肺，AAA与AXB-Dm以及AAA与AXB-Dw之间的差异显著大于AXB-Dm与AXB-Dw之间的差异。与AAA和AXB-Dw相比，即使对于较小的，AXB-Dm因剂量不均匀导致的生物等效剂量（BED，）降低超过6.5%。AAA、AXB-Dw和AXB-Dm计划中的等效均匀剂量平均值分别为52.03±.39 Gy、52.24 ±.81 Gy和51.13 ±.47 Gy。AAA、AXB-Dw和AXB-Dm计划中PTV的肿瘤控制概率（TCP）结果分别为62.29 ± 1.57%、62.82 ± 1.69%和58.68±1.88%。采用2%/2 mm和3%/3 mm的验收标准时，、和的平均值分别为87.24%、63.3%和64.81%，而对应的分别为97.86%、91.77%和89.25%。从AXB-Dm切换到AXB-Dw时理论计算与TPS之间的剂量差异约为1.63%。
当肿瘤尤其由不均匀组织组成时，AAA和AXB-Dw算法高估了放射生物学参数。相对较小的剂量差异可能导致相应TCP显著降低。物理师和肿瘤学家应谨慎选择剂量分布算法，以提高肿瘤控制并优化对OARs的保护。
