Department of Medical Radiation Physics, Lund University, Skåne University Hospital, Malmö, Sweden.
Phys Med Biol. 2010 Sep 7;55(17):4885-98. doi: 10.1088/0031-9155/55/17/001. Epub 2010 Aug 3.
The aim of this study was to verify the advanced inhomogeneous dose distribution produced by a volumetric arc therapy technique (RapidArc) using 3D gel measurements and Monte Carlo (MC) simulations. The TPS (treatment planning system)-calculated dose distribution was compared with gel measurements and MC simulations, thus investigating any discrepancy between the planned dose delivery and the actual delivery. Additionally, the reproducibility of the delivery was investigated using repeated gel measurements. A prostate treatment plan was delivered to a 1.3 liter nPAG gel phantom using one single arc rotation and a target dose of 3.3 Gy. Magnetic resonance imaging of the gel was carried out using a 1.5 T scanner. The MC dose distributions were calculated using the VIMC-Arc code. The relative absorbed dose differences were calculated voxel-by-voxel, within the volume enclosed by the 90% isodose surface (VOI(90)), for the TPS versus gel and TPS versus MC. The differences between the verification methods, MC versus gel, and between two repeated gel measurements were investigated in the same way. For all volume comparisons, the mean value was within 1% and the standard deviation of the differences was within 2.5% (1SD). A 3D gamma analysis between the dose matrices were carried out using gamma criteria 3%/3 mm and 5%/5 mm (% dose difference and mm distance to agreement) within the volume enclosed by the 50% isodose surface (VOI(50)) and the 90% isodose surface (VOI(90)), respectively. All comparisons resulted in very high pass rates. More than 95% of the TPS points were within 3%/3 mm of both the gel measurement and MC simulation, both inside VOI(50) and VOI(90). Additionally, the repeated gel measurements showed excellent consistency, indicating reproducible delivery. Using MC simulations and gel measurements, this verification study successfully demonstrated that the RapidArc plan was both accurately calculated and delivered as planned.
本研究旨在通过 3D 凝胶测量和蒙特卡罗（MC）模拟验证容积弧形治疗技术（RapidArc）产生的先进不均匀剂量分布。TPS（治疗计划系统）计算的剂量分布与凝胶测量和 MC 模拟进行比较，从而调查计划剂量输送与实际输送之间的任何差异。此外，还通过重复凝胶测量来研究输送的可重复性。使用一个单一的弧形旋转和 3.3Gy 的靶剂量将前列腺治疗计划输送到 1.3 升的 nPAG 凝胶体模中。使用 1.5T 扫描仪对凝胶进行磁共振成像。使用 VIMC-Arc 代码计算 MC 剂量分布。在由 90%等剂量曲面（VOI(90)）包围的体积内，对 TPS 与凝胶和 TPS 与 MC 进行逐像素计算相对吸收剂量差异。以相同的方式研究了验证方法 MC 与凝胶之间以及两次重复凝胶测量之间的差异。对于所有体积比较，平均值在 1%以内，差异的标准偏差在 2.5%（1SD）以内。使用 3%/3mm 和 5%/5mm（%剂量差异和 mm 协议距离）的伽马标准在由 50%等剂量曲面（VOI(50)）和 90%等剂量曲面（VOI(90)）包围的体积内进行剂量矩阵之间的 3D 伽马分析。所有比较都产生了非常高的通过率。TPS 点中有超过 95%在凝胶测量和 MC 模拟的 3%/3mm 内，无论是在 VOI(50)内还是 VOI(90)内。此外，重复的凝胶测量显示出极好的一致性，表明输送具有可重复性。使用 MC 模拟和凝胶测量，这项验证研究成功地证明了 RapidArc 计划的计算和输送都与计划一致。
