Kerns James R, Stingo Francesco, Followill David S, Howell Rebecca M, Melancon Adam, Kry Stephen F
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; Imaging and Radiation Oncology Core-Houston, The University of Texas MD Anderson Cancer Center, Houston, Texas; Graduate School of Biomedical Sciences, The University of Texas Health Science Center-Houston, Houston, Texas.
Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Int J Radiat Oncol Biol Phys. 2017 Aug 1;98(5):1197-1203. doi: 10.1016/j.ijrobp.2017.03.049. Epub 2017 Apr 4.
The anthropomorphic phantom program at the Houston branch of the Imaging and Radiation Oncology Core (IROC-Houston) is an end-to-end test that can be used to determine whether an institution can accurately model, calculate, and deliver an intensity modulated radiation therapy dose distribution. Currently, institutions that do not meet IROC-Houston's criteria have no specific information with which to identify and correct problems. In the present study, an independent recalculation system was developed to identify treatment planning system (TPS) calculation errors.
A recalculation system was commissioned and customized using IROC-Houston measurement reference dosimetry data for common linear accelerator classes. Using this system, 259 head and neck phantom irradiations were recalculated. Both the recalculation and the institution's TPS calculation were compared with the delivered dose that was measured. In cases in which the recalculation was statistically more accurate by 2% on average or 3% at a single measurement location than was the institution's TPS, the irradiation was flagged as having a "considerable" institutional calculation error. The error rates were also examined according to the linear accelerator vendor and delivery technique.
Surprisingly, on average, the reference recalculation system had better accuracy than the institution's TPS. Considerable TPS errors were found in 17% (n=45) of the head and neck irradiations. Also, 68% (n=13) of the irradiations that failed to meet the IROC-Houston criteria were found to have calculation errors.
Nearly 1 in 5 institutions were found to have TPS errors in their intensity modulated radiation therapy calculations, highlighting the need for careful beam modeling and calculation in the TPS. An independent recalculation system can help identify the presence of TPS errors and pass on the knowledge to the institution.
影像与放射肿瘤学核心（IROC）休斯顿分会的人体模型程序是一项端到端测试，可用于确定机构是否能够准确模拟、计算并交付调强放射治疗剂量分布。目前，未达到IROC休斯顿分会标准的机构没有用于识别和纠正问题的具体信息。在本研究中，开发了一个独立的重新计算系统以识别治疗计划系统（TPS）的计算错误。
使用IROC休斯顿分会针对常见直线加速器类型的测量参考剂量学数据来调试和定制一个重新计算系统。利用该系统，对259次头颈部模型照射进行了重新计算。将重新计算结果和机构的TPS计算结果与测量得到的实际交付剂量进行比较。如果重新计算在统计学上平均比机构的TPS更准确2%，或者在单个测量位置更准确3%，则将该照射标记为存在“显著”的机构计算错误。还根据直线加速器供应商和交付技术检查了错误率。
令人惊讶的是，平均而言，参考重新计算系统比机构的TPS具有更高的准确性。在17%（n = 45）的头颈部照射中发现了显著的TPS错误。此外，在未达到IROC休斯顿分会标准的照射中，68%（n = 13）被发现存在计算错误。
发现近五分之一的机构在其调强放射治疗计算中存在TPS错误，这凸显了在TPS中进行仔细的射束建模和计算的必要性。一个独立的重新计算系统可以帮助识别TPS错误的存在，并将相关信息反馈给机构。
