Shinoda Kazuya, Shida Koichi, Hatanaka Shogo
Department of Radiological Technology, Ibaraki Prefectural Central Hospital.
Department of Radiology, Toho University Medical Center Ohashi Hospital.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2020;76(4):404-409. doi: 10.6009/jjrt.2020_JSRT_76.4.404.
Multi-leaf collimator (MLC) parameters, which are registered with radiation treatment planning systems, are very important for intensity modulated radiation therapy (IMRT). In this study, we investigated MLC parameters of respective institutions for efficient commissioning of IMRT. Data of linac models, MLC types, nominal energy, irradiation technique, calculation algorithm, dosimetric leaf gap (DLG) values, and MLC transmission values were collected from each institution in which Varian linac and Eclipse were owned, and analyzed. The numbers of responses from institutions to questionnaire were 15, and the total number of linac was 22. In most institutions, volumetric modulated arc therapy (VMAT) technique was used, and the most used nominal energy was 10 MV. The higher nominal energy was, the higher values of MLC parameters (DLG and MLC transmission) were. In addition, values of MLC parameters of flattening filter free (FFF) beams were smaller than those of flattening filter (FF) beams, even when nominal energy was same. Values of DLG of VMAT tended to be greater than those of multi-field IMRT. These results are expected to be useful for institutions, in which IMRT is implemented.
与放射治疗计划系统配准的多叶准直器（MLC）参数对于调强放射治疗（IMRT）非常重要。在本研究中，我们调查了各机构的MLC参数，以实现IMRT的高效调试。从每个拥有瓦里安直线加速器和Eclipse的机构收集直线加速器型号、MLC类型、标称能量、照射技术、计算算法、剂量学叶间距（DLG）值和MLC透射值的数据，并进行分析。机构对问卷的回复数量为15份，直线加速器总数为22台。在大多数机构中，使用了容积调强弧形治疗（VMAT）技术，最常用的标称能量为10MV。标称能量越高，MLC参数（DLG和MLC透射）的值越高。此外，即使标称能量相同，无均整器（FFF）射束的MLC参数值也小于有均整器（FF）射束的参数值。VMAT的DLG值往往大于多野IMRT的DLG值。这些结果有望对实施IMRT的机构有用。
