Woon Wui Ann, Ravindran Paul B, Ekayanake Piyasiri, Vikraman Subramani, Amirah Siti, Lim Yivonne Y F, Vun Christopher H S, Khalid Jamsari
Department of Radiation Oncology, The Brunei Cancer Center, Bandar Seri Begawan BG3122, Brunei Darussalam.
Faculty of Science, Universiti Brunei Darussalam, Bandar Seri Begawan BE1410, Brunei Darussalam.
Rep Pract Oncol Radiother. 2018 Sep-Oct;23(5):346-359. doi: 10.1016/j.rpor.2018.07.006. Epub 2018 Aug 13.
The aim of this study was to investigate the sensitivity of the trajectory log file based quality assurance to detect potential errors such as MLC positioning and gantry positioning by comparing it with EPID measurement using the most commonly used criteria of 3%/3 mm.
An in-house program was used to modified plans using information from log files, which can then be used to recalculate a new dose distribution. The recalculated dose volume histograms (DVH) were compared with the originals to assess differences in target and critical organ dose. The dose according to the differences in DVH was also compared with dosimetry from an electronic portal imaging device.
In all organs at risk (OARs) and planning target volumes (PTVs), there was a strong positive linear relationship between MLC positioning and dose error, in both IMRT and VMAT plans. However, gantry positioning errors exhibited little impact in VMAT delivery. For the ten clinical cases, no significant correlations were found between gamma passing rates under the criteria of 3%/3 mm for the composite dose and the mean dose error in DVH ( < 0.3, > 0.05); however, a significant positive correlation was found between the gamma passing rate of 3%/3 mm (%) averaged over all fields and the mean dose error in the DVH of the VMAT plans ( = 0.59, < 0.001).
This study has successfully shown the sensitivity of the trajectory log file to detect the impact of systematic MLC errors and random errors in dose delivery and analyzed the correlation of gamma passing rates with DVH.
本研究的目的是通过将基于轨迹日志文件的质量保证与使用最常用的3%/3毫米标准的电子射野影像装置（EPID）测量结果进行比较，来调查其检测潜在误差（如多叶准直器（MLC）定位和机架定位）的敏感性。
使用一个内部程序，利用日志文件中的信息修改计划，然后可用于重新计算新的剂量分布。将重新计算的剂量体积直方图（DVH）与原始数据进行比较，以评估靶区和关键器官剂量的差异。还将根据DVH差异得出的剂量与电子射野影像装置的剂量测定结果进行比较。
在调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）计划中，在所有危及器官（OAR）和计划靶区（PTV）中，MLC定位与剂量误差之间均存在强正线性关系。然而，机架定位误差在VMAT照射中影响较小。对于这10个临床病例，在3%/3毫米标准下的复合剂量伽马通过率与DVH中的平均剂量误差之间未发现显著相关性（<0.3，>0.05）；然而，在所有射野平均的3%/3毫米（%）伽马通过率与VMAT计划DVH中的平均剂量误差之间发现显著正相关（=0.59，<0.001）。
本研究成功展示了轨迹日志文件检测剂量传递中系统MLC误差和随机误差影响的敏感性，并分析了伽马通过率与DVH的相关性。
