Department of Radiation Oncology, MR Linac ART Division, Graduate School of Medicine, Chiba University, Chuo-ku, Chiba, Japan.
Department of Radiation Sciences, Komazawa University, Setagaya-ku, Tokyo, Japan.
J Appl Clin Med Phys. 2023 Jul;24(7):e14071. doi: 10.1002/acm2.14071. Epub 2023 Jun 16.
Dosimetric accuracy is critical when a patient treated with volumetric modulated arc therapy (VMAT) is transferred to another beam-matched linac. To evaluate the performance of Accelerated Go Live (AGL) service, the measured beam characteristics and patient specific quality assurance (QA) results between two AGL-matched linacs were compared.
Two VersaHD linacs were installed using the AGL service. After the installation, the beam data such as percentage depth dose (PDD), lateral profiles and output factors for all photon beams were measured. Relative doses were also measured as a function of the multi-leaf collimator (MLC) leaf gap width. Subsequently, VMAT plans were created for prostate, pelvis, head and neck, liver, lung cancers and multiple brain metastases. Dose distributions and point doses were measured by multi-dimensional detectors and ionization chambers for patient specific quality assurance, and comparisons were made between the two linacs.
Dose differences in PDDs were all within ± 1% except the entrance region, and the averaged gamma indices of the lateral profiles were within 0.3. The differences in doses as a function of the MLC leaf gap width between the two linacs were within ±0.5%. For all the plans, gamma passing rates were all higher than 95% with criteria of 2%/2 mm. The average and the SD of dose differences on the multi-dimensional detector between both measurements was 0.06 ± 2.12%, and the average of point dose differences was -0.03 ± 0.33%.
We have evaluated the AGL performance in the context of beam characteristics and patient specific QA. It was demonstrated that the AGL service provides an accurate VMAT treatment reproducibility for many tumor sites with gamma pass rates greater than 95% under criteria of 2%/2 mm.
当接受容积调强弧形治疗（VMAT）的患者转至另一台光束匹配的直线加速器时，剂量准确性至关重要。为了评估加速上线（AGL）服务的性能，比较了两台 AGL 匹配的直线加速器之间的测量光束特性和患者特定质量保证（QA）结果。
两台 VersaHD 直线加速器使用 AGL 服务进行安装。安装后，测量了所有光子光束的百分深度剂量（PDD）、横向轮廓和输出因子等光束数据。还测量了多叶准直器（MLC）叶片间隙宽度的相对剂量。随后，为前列腺、骨盆、头颈部、肝脏、肺部癌症和多个脑转移瘤创建了 VMAT 计划。使用多维探测器和电离室对剂量分布和点剂量进行了患者特定质量保证测量，并对两台直线加速器进行了比较。
PDD 中的剂量差异均在±1%以内，除了入口区域，横向轮廓的平均伽马指数在 0.3 以内。两台直线加速器之间 MLC 叶片间隙宽度的剂量差异在±0.5%以内。所有计划的伽马通过率均高于 95%，标准为 2%/2mm。两次测量的多维探测器上剂量差异的平均值和标准差为 0.06±2.12%，点剂量差异的平均值为-0.03±0.33%。
我们已经在光束特性和患者特定 QA 的背景下评估了 AGL 的性能。结果表明，AGL 服务在 2%/2mm 的标准下，提供了大于 95%的伽马通过率，为许多肿瘤部位提供了准确的 VMAT 治疗可重复性。
