Thomas M, Chandroth M
Department of Oncology, Waikato District Health Board, Hamilton, 3240, New Zealand,
Australas Phys Eng Sci Med. 2014 Mar;37(1):59-74. doi: 10.1007/s13246-014-0241-5. Epub 2014 Jan 11.
The aim of this study was to generate a local confidence limit (CL) for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques used at Waikato Regional Cancer Centre. This work was carried out based on the American Association of Physicists in Medicine (AAPM) Task Group (TG) 119 report. The AAPM TG 119 report recommends CLs as a bench mark for IMRT commissioning and delivery based on its multiple institutions planning and dosimetry comparisons. In this study the locally obtained CLs were compared to TG119 benchmarks. Furthermore, the same bench mark was used to test the capabilities and quality of the VMAT technique in our clinic. The TG 119 test suite consists of two primary and four clinical tests for evaluating the accuracy of IMRT planning and dose delivery systems. Pre defined structure sets contoured on computed tomography images were downloaded from AAPM website and were transferred to a locally designed phantom. For each test case two plans were generated using IMRT and VMAT optimisation. Dose prescriptions and planning objectives recommended by TG119 report were followed to generate the test plans in Eclipse Treatment Planning System. For each plan the point dose measurements were done using an ion chamber at high dose and low dose regions. The planar dose distribution was analysed for percentage of points passing the gamma criteria of 3%/3 mm, for both the composite plan and individual fields of each plan. The CLs were generated based on the results from the gamma analysis and point dose measurements. For IMRT plans, the CLs obtained were (1) from point dose measurements: 2.49% at high dose region and 2.95% for the low dose region (2) from gamma analysis: 2.12% for individual fields and 5.9% for the composite plan. For VMAT plans, the CLs obtained were (1) from point dose measurements: 2.56% at high dose region and 2.6% for the low dose region (2) from gamma analysis: 1.46% for individual fields and 0.8% for the composite plan. All these CLs were well within the TG119 recommended bench marks. Based on these analysis which were performed in line with the TG119 recommendations, it is evident that the local clinic has commissioned IMRT and VMAT techniques with adequate accuracy. These results compliment our clinical confidence of using IMRT and VMAT routinely and expanding to different clinical sites.
本研究的目的是为怀卡托地区癌症中心使用的调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）技术生成局部置信限（CL）。这项工作是基于美国医学物理学家协会（AAPM）任务组（TG）119报告开展的。AAPM TG 119报告推荐将置信限作为IMRT调试和交付的基准，这是基于其多个机构的计划和剂量测定比较得出的。在本研究中，将本地获得的置信限与TG119基准进行了比较。此外，使用相同的基准来测试我们诊所VMAT技术的能力和质量。TG 119测试套件由两项主要测试和四项临床测试组成，用于评估IMRT计划和剂量输送系统的准确性。从AAPM网站下载在计算机断层扫描图像上勾勒出的预定义结构集，并将其转移到本地设计的体模中。对于每个测试病例，使用IMRT和VMAT优化生成两个计划。遵循TG119报告推荐的剂量处方和计划目标，在Eclipse治疗计划系统中生成测试计划。对于每个计划，在高剂量和低剂量区域使用电离室进行点剂量测量。分析平面剂量分布，以确定复合计划和每个计划的各个射野通过3%/3毫米伽马标准的点的百分比。基于伽马分析和点剂量测量的结果生成置信限。对于IMRT计划，获得的置信限为：（1）来自点剂量测量：高剂量区域为2.49%，低剂量区域为2.95%；（2）来自伽马分析：单个射野为2.12%，复合计划为5.9%。对于VMAT计划，获得的置信限为：（1）来自点剂量测量：高剂量区域为2.56%，低剂量区域为2.6%；（2）来自伽马分析：单个射野为1.46%，复合计划为0.8%。所有这些置信限均远低于TG119推荐的基准。基于按照TG119建议进行的这些分析，很明显本地诊所以足够的准确性调试了IMRT和VMAT技术。这些结果增强了我们对常规使用IMRT和VMAT并将其扩展到不同临床部位的临床信心。
