Department of Radiation Oncology, Fujian Medical University Union Hospital, Fuzhou, China.
Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA.
J Xray Sci Technol. 2018;26(4):657-666. doi: 10.3233/XST-17364.
Differences often exist in the dose calculation accuracy caused by using different dose calculation algorithms in non-uniform tissues.
To evaluate the accuracy of dose calculation with inhomogeneity correction in intensity-modulated radiation therapy (IMRT) by comparing dose calculated in Monaco with measurements in lung-chest phantom for esophagus cancer treatments.
Finite size pencil beam (FSPB) and X-ray voxel Monte Carlo (XVMC) were used respectively for IMRT dose recalculations. Ten IMRT plans were recalculated and measured in the chest-lung phantom. The dose measurements using the Gafchromic ® (EBT3) dosimetry films were validated with open fields in the interfaces of materials with various physical densities. The accuracy of dose calculations was then evaluated by both point dose comparison and Gamma analysis against the film measurements.
For regular open fields, the discrepancies of the point doses were less than 3.0% and 2.0% between measurement and calculations by FSPB and XVMC, respectively. For 6 MV IMRT plans, the average passing rates based on 3% /3 mm Gamma criteria were 82.8±1.0% and 96.4±0.7% for FSPB and XVMC, respectively.
The XVMC algorithms more accurate in IMRT dose calculations with inhomogeneity correction for esophagus cancer.
在不均匀组织中使用不同的剂量计算算法会导致剂量计算精度存在差异。
通过比较 Monaco 计算的剂量与肺胸体模中食管癌治疗的测量值，评估不均匀性校正在调强放射治疗（IMRT）中的剂量计算准确性。
分别使用有限大小铅笔束（FSPB）和 X 射线体素蒙特卡罗（XVMC）进行 IMRT 剂量重新计算。在胸肺体模中对 10 个 IMRT 计划进行重新计算和测量。使用 Gafchromic ® （EBT3）剂量测定胶片进行剂量测量，并在具有不同物理密度的材料界面处使用开放场进行验证。然后，通过点剂量比较和与胶片测量的伽马分析评估剂量计算的准确性。
对于常规开放场，FSPB 和 XVMC 的点剂量测量值与计算值之间的差异分别小于 3.0%和 2.0%。对于 6 MV IMRT 计划，基于 3%/3mm Gamma 标准的平均通过率分别为 FSPB 和 XVMC 的 82.8±1.0%和 96.4±0.7%。
在食管癌的 IMRT 剂量计算中，XVMC 算法在不均匀性校正方面更准确。
