Zabihzadeh Mansour, Rahimi Azizollah, Shahbazian Hodjatollah, Razmjoo Sasan, Mahdavi Seyyed Rabie
PhD, Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
PhD, Department of Clinical Oncology, Faculty of Medicine, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
J Biomed Phys Eng. 2021 Aug 1;11(4):483-496. doi: 10.31661/jbpe.v0i0.1097. eCollection 2021 Aug.
It is recommended for each set of radiation data and algorithm that subtle deliberation is done regarding dose calculation accuracy. Knowing the errors in dose calculation for each treatment plan will result in an accurate estimate of the actual dose achieved by the tumor.
This study aims to evaluate the equivalent path length (EPL) and equivalent tissue air ratio (ETAR) algorithms in radiation dose calculation.
In this experimental study, the TEC-DOC 1583 guideline was used. Measurements and calculations were obtained for each algorithm at specific points in thorax CIRS phantom for 6 and 18 MVs and results were compared.
In the EPL, calculations were in agreement with measurements for 27 points and differences between them ranged from 0.1% to 10.4% at 6 MV. The calculations were in agreement with measurements for 21 points and differences between them ranged from 0.4% to 13% at 18 MV. In ETAR, calculations were also in consistent with measurements for 21 points, and differences between them ranged from 0.1% to 9% at 6 MV. Moreover, for 18 MV, the calculations were in agreement with measurements for 17 points and differences between them ranged from 0% to 11%.
For the EPL algorithm, more dose points were in consistent with acceptance criteria. The errors in the ETAR were 1% to 2% less than the EPL. The greatest calculation error occurs in low-density lung tissue with inhomogeneities or in high-density bone. Errors were larger in shallow depths. The error in higher energy was more than low energy beam.
对于每组辐射数据和算法，建议对剂量计算准确性进行细致考量。了解每个治疗计划的剂量计算误差将有助于准确估计肿瘤实际接受的剂量。
本研究旨在评估等效路径长度（EPL）和等效组织空气比（ETAR）算法在辐射剂量计算中的应用。
在本实验研究中，采用了TEC-DOC 1583指南。针对6兆伏和18兆伏的情况，在胸部CIRS体模的特定点对每种算法进行测量和计算，并比较结果。
在EPL算法中，6兆伏时27个点的计算结果与测量值相符，两者差异在0.1%至10.4%之间。18兆伏时21个点的计算结果与测量值相符，两者差异在0.4%至13%之间。在ETAR算法中，6兆伏时21个点的计算结果也与测量值一致，两者差异在0.1%至9%之间。此外，18兆伏时17个点的计算结果与测量值相符，两者差异在0%至11%之间。
对于EPL算法，更多的剂量点符合验收标准。ETAR算法的误差比EPL算法小1%至2%。最大的计算误差出现在存在不均匀性的低密度肺组织或高密度骨组织中。浅深度处的误差更大。高能束的误差比低能束的误差更大。
