Department of Medical Physics, Apollo Proton Cancer Centre, 100 Feet Road Tharamani, Chennai, 600096, Tamil Nadu, India.
School of Advanced Sciences, VIT University, Vellore, 632014, India.
Radiat Oncol. 2020 Oct 14;15(1):236. doi: 10.1186/s13014-020-01669-2.
There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for Total Marrow (TMI) and Lymphoid (TMLI) Irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured Leaf Open Time Sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with (a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and (b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98% (D) and 2% (D) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ± 1.80% of planned and IC measurement. The planned dose distribution agreed with reconstructed and ArcCheck measured dose with mean (SD) 3Dγ of 98.70% (1.57%) and 2Dγ of 99.48% (0.81%). The deviation in D and D were within 1.71% and 4.10% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agreed within ± 1.20%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from the five upper body TMI/TMLI plans showed mean ± SD 2Dγ of 97.82% ± 1.27%, the reconstruction method resulted poor mean (SD) 3Dγ of 92.00% (± 5.83%), 64.80% (± 28.28%), 69.20% (± 30.46%), 60.80% (± 19.37%) and 73.2% (± 20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D and D of all PTVs were < 3.80% and 9.50%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D and D < 1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5 cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.
对于全骨髓（TMI）和淋巴（TMLI）照射计划，没有理想的探测器-体模组合来进行特定患者的质量保证（PSQA）。在这项研究中，使用兆伏计算机断层扫描探测器测量叶开时间正弦图（LOTS）进行三维剂量重建，以研究螺旋断层放疗中 TMI/TMLI 患者的 PSQA。首先通过比较（a）离子室（IC）和螺旋探测器阵列（ArcCheck）测量值与（b）使用 3%@3mm 和剂量到 98%（D）和 2%（D）的 3Dγ分析与计划剂量分布，对 10 名非 TMI/TMLI 患者的这种方法的可行性进行了验证PTVs。对于来自 5 名 TMI/TMLI 患者的 10 个治疗计划，进行了相同的比较。在所有非 TMI/TMLI 患者中，重建的绝对剂量与计划和 IC 测量值相差在 1.80%以内。计划的剂量分布与重建和 ArcCheck 测量的剂量一致，3Dγ 的平均值（标准差）为 98.70%（1.57%）和 2Dγ 的平均值（标准差）为 99.48%（0.81%）。D 和 D 的偏差分别在 1.71%和 4.10%以内。在所有 25 名来自 TMI/TMLI 患者的测量位置中，计划和 IC 测量的绝对剂量在 1.20%以内。尽管使用 ArcCHECK 测量对来自 5 名上半身 TMI/TMLI 计划的 PTVs 胸部进行扇形通量验证的结果显示，PTVs 胸部的 2Dγ 的平均值（标准差）为 97.82%（1.27%），但重建方法的结果较差，平均（标准差）为 3Dγ 为 92.00%（±5.83%）、64.80%（±28.28%）、69.20%（±30.46%）、60.80%（±19.37%）和 73.2%（±20.36%），分别为 PTVs 脑、胸、躯干、肢体和上半身。所有 PTVs 的中位数 D 和 D 的偏差均<3.80%和 9.50%。对上半身 TMI/TMLI 计划的所有重新优化均采用新的螺距和调制因子 0.3 和 3，可显著提高所有 PTVs 的 3Dγ 至 100%，中位数 D 和 D<1.6%。基于 LOTS 的 TMI/TMLI PSQA 准确、稳健且高效。建议上半身 TMI/TMLI 计划的射野宽度、螺距和调制因子分别为 5cm、0.3 和 3，以获得更好的剂量学结果和 PSQA 结果。
