放射治疗加速器经历了持续的技术发展。我们研究了Radixact™和VMAT治疗计划之间的差异。本研究纳入60例患者，针对6种肿瘤部位（全脑、头颈部、淋巴瘤、肺、前列腺和直肠），进行了Radixact™和VMAT计划的剂量比较。VMAT计划是使用两台Elekta线性加速器（Synergy®和Versa HD™）生成的。考虑了计划目标体积（PTV）覆盖度、危及器官剂量约束和4个剂量指标，使用质量保证（伽马指数评估）测量来评估计划的可执行性，临床判断被包括在评估中。平均AAPM TG218（3％-2mm，全局归一化）伽马指数值分别为Radixact™，Versa HD™和Synergy®的96.6％，97.8％和99.4％。Radixact™在剂量指标、海马D100％、脊髓Dmax、直肠V38.4 Gy、膀胱V30 Gy和V40 Gy方面表现优于Versa HD™。而Versa HD™则在（肺-PTV）V5 Gy和（肺-PTV）Dmean、心脏Dmean、乳房V4 Gy和肠道V45 Gy方面表现更好。关于Synergy®，头颈部Radixact™计划节省了更多副甲状腺、口腔和会厌旁区。从临床角度而言，对于头颈部、前列腺和直肠部位，Radixact™和Versa HD™计划相似；Radixact™计划在头颈部和直肠部位优于Synergy®计划。放射治疗计划的质量已经得到改善，并且与调强放射治疗的差异已经减小。但是，调强放疗仍然是多台机器部门中不可或缺的附加设备。©2023。作者（根据日本放射技术协会和日本医学物理协会的独家许可）

Radiotherapy accelerators have undergone continuous technological developments. We investigated the differences between Radixact™ and VMAT treatment plans. Sixty patients were included in this study. Dosimetric comparison between the Radixact™ and VMAT plans was performed for six cancer sites: whole-brain, head and neck, lymphoma, lung, prostate, and rectum. The VMAT plans were generated with two Elekta linear accelerators (Synergy® and Versa HD™). The planning target volume (PTV) coverage, organs-at-risk dose constraints, and four dosimetric indexes were considered. The deliverability of the plans was assessed using quality assurance (gamma index evaluation) measurements; clinical judgment was included in the assessment. The mean AAPM TG218 (3%-2 mm, global normalization) gamma index values were 99.4%, 97.8%, and 96.6% for Radixact™, Versa HD™, and Synergy®, respectively. Radixact™ performed better than Versa HD™ in terms of dosimetric indexes, hippocampi D100%, spinal cord Dmax, rectum V38.4  Gy, bladder V30 Gy, and V40 Gy. Versa HD™ saved more of the (lungs-PTV) V5 Gy and (lungs-PTV) Dmean, heart Dmean, breasts V4 Gy, and bowel V45 Gy. Regarding Synergy®, the head and neck Radixact™ plan saved more of the parotid gland, oral cavity, and supraglottic larynx. From a clinical point of view, for the head and neck, prostate, and rectal sites, the Radixact™ and Versa HD™ plans were similar; Radixact™ plans were preferable for the head and neck and rectum to Synergy® plans. The quality of linac plans has improved, and differences with tomotherapy have decreased. However, tomotherapy continues to be an essential add-on in multi-machine departments.© 2023. The Author(s), under exclusive licence to Japanese Society of Radiological Technology and Japan Society of Medical Physics.