Quino L Vazquez, Stathakis S, Gutierrez A, Esquivel C, Alkhatib H, Papanikolaou N
University of Texas Health Science Center at San Antonio, San Antonio, TX.
Richland Memorial Hospital, Columbia, SC.
Med Phys. 2012 Jun;39(6Part28):3967. doi: 10.1118/1.4736188.
A software program (MU-EPID) has been developed to perform patient specific IMRT pre-treatment QA verification using an electronic portal imaging device.
The software converts measured images of intensity modulated beams delivered to an EPID, into fluence maps that can be imported in the treatment planning system. The dose can then be calculated in the patient anatomy and compared against the patient's treatment plan for QA purposes. We first benchmarked the software using as a patient a cylindrical phantom. An aSi-1000 EPID mounted on a Varian Novalis linear accelerator was used for the image acquisition. Finally, IMRT plans from different treatment sites were used to further validate this in- house software. QA analysis was performed by evaluation of isodose distributions, DVH comparison and 2D gamma analysis.
The validation study with the cylindrical phantom showed that the dose to the ion chamber measurement point was in good agreement with both the original treatment plan and the MU-EPID reconstructed dose. Similar results were found for the clinical cases that we studied. A gamma analysis of the dose to the isocenter plane was performed for each plan. Using 3% and 3 mm as the evaluation criteria, resulted in an average of 97.44% of pixels passing the analysis (gamma<1). Good agreement was also observed for the DVH, isodose and profile comparisons between the clinically delivered IMRT plan and the MU-EPID derived dose calculation.
The results of the present investigation suggest that MU-EPID can be used in a clinical environment and can be used for patient specific QA for IMRT plans. This work has been supported by the SCOA.
已开发出一款软件程序（MU-EPID），用于使用电子射野影像装置进行患者特异性调强放疗（IMRT）治疗前质量保证（QA）验证。
该软件将输送至电子射野影像装置（EPID）的调强射束的测量图像转换为可导入治疗计划系统的注量图。然后可在患者解剖结构中计算剂量，并与患者的治疗计划进行比较以进行QA。我们首先以圆柱形模体作为患者对该软件进行基准测试。使用安装在瓦里安诺瓦利斯直线加速器上的非晶硅1000 EPID进行图像采集。最后，使用来自不同治疗部位的IMRT计划进一步验证这款内部软件。通过评估等剂量分布、剂量体积直方图（DVH）比较和二维伽马分析进行QA分析。
对圆柱形模体的验证研究表明，电离室测量点的剂量与原始治疗计划以及MU-EPID重建剂量均高度一致。我们研究的临床病例也得到了类似结果。对每个计划的等中心平面剂量进行伽马分析。以3%和3毫米作为评估标准，平均有97.44%的像素通过分析（伽马<1）。在临床实施的IMRT计划与MU-EPID导出的剂量计算之间的DVH、等剂量和轮廓比较方面也观察到了良好的一致性。
本研究结果表明，MU-EPID可用于临床环境，可用于IMRT计划的患者特异性QA。这项工作得到了SCOA的支持。
