Investigating the effectiveness of monitoring relevant variations during IMRT and VMAT treatments by EPID-based 3D in vivo verification performed using planning CTs
Investigating the effectiveness of monitoring relevant variations during IMRT and VMAT treatments by EPID-based 3D in vivo verification performed using planning CTs
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DOI：
10.1371/journal.pone.0218803
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发表时间：
2019-06-28
期刊：
影响因子：
3.7
通讯作者：
Liu, Xiaowei
中科院分区：
文献类型：
--
作者：
Li, Yinghui;Zhu, Jinhan;Liu, Xiaowei
本研究的目的是探讨在使用计划CT进行基于电子射野成像设备（EPID）的3D体内验证的治疗过程中监测相关变化的有效性。（均匀和非均匀体模）和胸部体模进行了分析，并分析了六个相关变量，包括机器输出，计划靶体积（PTV）变形，评价了多叶准直器（MLC）和体模移位（设置误差）以及机架和治疗床角度移位。3D伽马和剂量体积直方图（DVH）方法分别用于评估基于EPID的3D体内剂量测定的检测灵敏度和EPID重建的剂量准确度，结果简单体模的结果表明，EPID重建的伽马失效率和DVH趋势是与机器输出和MLC移位的TPS模拟结果一致，与体模移位、机架/治疗床角度移位和PTV变形变化不一致。胸部体模的结果表明，CBCT引导下EPID重建能灵敏地检测到胸部体模中3 mm的体模偏移，其伽马失效率和DVH趋势与TPS模拟结果一致。与体模无关并导致直线加速器射束变化的电子束可被EPID灵敏地检测到。基于3D的体内剂量测定，并且不影响EPID重建剂量的准确性。对于体模相关变化（例如体模移位和机架/治疗床角度移位），计划CT将限制基于EPID的3D体内剂量测定的检测灵敏度和重建剂量的准确性。EPID重建结合IGRT技术是一种更有效的监测体模位移变化的方法。
PurposeThe goal of this study was to investigate the effectiveness of monitoring relevant variations during treatments for electronic portal imaging device ( EPID)-based 3D in vivo verification performed using planning CTs.MethodsExperiments on two simple phantoms ( uniform and nonuniform phantoms) and a thoracic phantom were analyzed in this study, and six relevant variations including the machine output, planning target volume ( PTV) deformation, multileaf collimator ( MLC) and Phantom shift ( set-up errors), and gantry and couch angle shifts were evaluated. 3D gamma and dose-volume histogram ( DVH) methods were used to evaluate the detection sensitivity of the EPID-based 3D in vivo dosimetry and the dose accuracy of the EPID reconstruction, respectively, as affected by the variations, and the results were validated by determining the consistency with TPS simulated results.ResultsThe results of the simple phantoms showed that the gamma failure rates and DVH trend of EPID reconstructions were consistent with the results of TPS simulations for machine output and MLC shifts and inconsistent for phantom shift, gantry/couch angle shift and PTV deformation variations. The results of the thoracic phantom showed that CBCT-guided EPID reconstruction sensitively detected 3-mm Phantom shift in thoracic phantom and its gamma failure rates and DVH trend were consistent with the results of TPS simulations.ConclusionThe variations, such as machine output and MLC shift, that are phantom unrelated and cause changes in the beam of the linear accelerator can be sensitively detected by EPID-based 3D in vivo dosimetry and do not affect the accuracy of the EPID reconstruction dose. Planning CT will limit the detection sensitivity and the accuracy of the reconstruction dose of the EPID-based 3D in vivo dosimetry for phantom-related variations ( such as Phantom shift and gantry/couch angle shift). EPID reconstruction combined with IGRT technology is a more effective method to monitor phantom shift variations.