Hasani Mohsen, Farhood Bagher, Ghorbani Mahdi, Naderi Hamideh, Saadatmand Sepideh, Karimkhani Zandi Saeed, Knaup Courtney
Department of Radiotherapy Physics, Cancer Research Centre, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran.
Department of Medical Physics and Radiology, Faculty of Paramedical Sciences, Kashan University of Medical Sciences, Kashan, Iran.
Australas Phys Eng Sci Med. 2019 Jun;42(2):489-502. doi: 10.1007/s13246-019-00745-6. Epub 2019 Mar 8.
The accuracy of a computed tomography (CT)-relative electron density (RED) curve may have an indirect impact on the accuracy of dose calculation by a treatment planning system (TPS). This effect has not been previously quantified for input of different CT-RED curves from different CT-scan units in the Monaco TPS. This study aims to evaluate the effect of CT-RED curve on the dose calculation by the Monaco radiotherapy TPS. Four CT images of the CIRS phantom were obtained by different CT scanners. The accuracy of the dose calculation in the three algorithms of the Monaco TPS (Monte Carlo, collapse cone, and pencil beam) is also evaluated based on TECDOC 1583. The CT-RED curves from the CT scanners were transferred to the Monaco TPS to audit the different algorithms of the TPS. The dose values were measured with an ionization chamber in the CIRS phantom. Then, the dose values were calculated by the Monaco algorithms in the corresponding points. For the Monaco TPS and based on TECDOC 1583, the accuracy of the dose calculation in all the three algorithms is within the agreement criteria for most of the points evaluated. For low dose regions, the differences between the calculated and measured dose values are higher than the agreement criteria in a number of points. For the majority of the points, the algorithms underestimate the calculated dose values. It was also found that the use of different CT-RED curves can lead to minor discrepancies in the dose calculation by the Monaco TPS, especially in low dose regions. However, it appears that these differences are not clinically significant in most of the cases.
计算机断层扫描（CT）相对电子密度（RED）曲线的准确性可能会对治疗计划系统（TPS）剂量计算的准确性产生间接影响。对于在Monaco TPS中输入来自不同CT扫描单元的不同CT-RED曲线，这种影响此前尚未进行量化。本研究旨在评估CT-RED曲线对Monaco放射治疗TPS剂量计算的影响。通过不同的CT扫描仪获取了CIRS体模的四张CT图像。还基于TECDOC 1583评估了Monaco TPS三种算法（蒙特卡罗、塌陷锥和笔形束）中剂量计算的准确性。将来自CT扫描仪的CT-RED曲线传输到Monaco TPS，以审核TPS的不同算法。在CIRS体模中使用电离室测量剂量值。然后，通过Monaco算法在相应点计算剂量值。对于Monaco TPS并基于TECDOC 1583，在大多数评估点上，所有三种算法中剂量计算的准确性均在一致性标准范围内。对于低剂量区域，在一些点上计算剂量值与测量剂量值之间的差异高于一致性标准。对于大多数点，算法低估了计算的剂量值。还发现，使用不同的CT-RED曲线会导致Monaco TPS在剂量计算中出现微小差异，尤其是在低剂量区域。然而，在大多数情况下，这些差异似乎并无临床意义。
