Gershkevitsh Eduard, Schmidt Rainer, Velez Graciela, Miller Dan, Korf Erhardt, Yip Fernando, Wanwilairat Somsak, Vatnitsky Stanislav
North Estonia Regional Hospital, Tallinn, Estonia.
Radiother Oncol. 2008 Dec;89(3):338-46. doi: 10.1016/j.radonc.2008.07.007. Epub 2008 Aug 11.
The methodology developed by IAEA for dosimetric quality control of treatment planning systems has been tested in different hospitals through a pilot study. The aim was to verify the methodology and observe the range of deviations between planned and delivered doses in 3D conformal radiotherapy in situations close to a clinical setting.
The methodology was based on an anthropomorphic phantom representing the human thorax, and simulates the whole chain of external beam radiotherapy treatment planning activities. The phantom was scanned using computed tomography and eight test cases were planned on treatment planning systems which imitate different irradiation geometries found in conformal radiotherapy. The doses were measured with ion chambers, and the deviation between measured and treatment planning system calculated doses was reported. This methodology, which employs the same phantom and the same set of test cases, was tested in 17 different hospitals which were using 14 different algorithms/inhomogeneity correction methods implemented in different treatment planning systems.
A total of 53 clinical test case datasets for different energies and calculation algorithms were produced. Most of the systems with advanced algorithms complied with predefined agreement criteria. Dose differences more than 20% were discovered for some of the simple algorithms and high energy X-ray beams. The number of deviations outside agreement criteria increases with the beam energy and decreases with advancement of the treatment planning system calculation algorithm.
Large deviations exist in some simple dose calculation algorithms, therefore more advanced algorithms would be preferable and therefore should be implemented in clinical practice. The test cases that could be performed in reasonable time would help the users to appreciate the possibilities of their system and understand its limitations.
国际原子能机构（IAEA）开发的治疗计划系统剂量学质量控制方法已通过一项试点研究在不同医院进行了测试。目的是验证该方法，并观察在接近临床环境的情况下三维适形放射治疗中计划剂量与 delivered 剂量之间的偏差范围。
该方法基于一个代表人体胸部的拟人化体模，并模拟外照射放射治疗治疗计划活动的整个流程。使用计算机断层扫描对体模进行扫描，并在模拟适形放射治疗中发现的不同照射几何形状的治疗计划系统上规划了八个测试病例。使用电离室测量剂量，并报告测量剂量与治疗计划系统计算剂量之间的偏差。这种使用相同体模和相同测试病例集的方法在17家不同医院进行了测试，这些医院使用了在不同治疗计划系统中实现的14种不同算法/不均匀性校正方法。
共生成了53个针对不同能量和计算算法的临床测试病例数据集。大多数采用先进算法的系统符合预定义的一致性标准。对于一些简单算法和高能X射线束，发现剂量差异超过20%。超出一致性标准的偏差数量随束能量增加而增加，随治疗计划系统计算算法的进步而减少。
一些简单的剂量计算算法存在较大偏差，因此更先进的算法更可取，应在临床实践中实施。能够在合理时间内执行的测试病例将帮助用户了解其系统的可能性并理解其局限性。
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