Matsumoto Kenji, Otsuka Masakazu, Tamura Mikoto, Monzen Hajime, Okumura Masahiko
Department of Central Radiology, Kindai University Hospital.
Department of Medical Physics, Graduate School of Medical Science, Kindai University.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2020;76(4):339-345. doi: 10.6009/jjrt.2020_JSRT_76.4.339.
Novel linac improvements in speed of gantry, collimator, leaf and dose rate may increase the time-efficiency of volumetric modulated arc therapy (VMAT) delivery, however remains to be investigated. In this study, a fast-rotating O-ring linac (Halcyon) with fast moving leaves is compared with a general linac (TrueBeam: TB) in terms of plan quality for VMAT of C-shape, prostate, multi target and, head and neck (H&N) cases from AAPM TG-119.
For the four test cases, VMAT planning was performed using single to four-arc VMAT on a Halcyon and using single to three-arc VMAT on a TrueBeam. Same conditions for optimization were used in each test case. Target coverage metrics and organ at risks (OAR) dose were compared. Monitor unit (MU) and irradiation time in each plan were also compared.
In all cases, single-arc plans of Halcyon were inferior to TB plans on dose objectives. Conformity index (CI) to outer target of C-shape case was better for Halcyon (1-arc: 1.242, 2-arc: 1.202, 3-arc: 1.198, 4-arc: 1.181) than for TB (1-arc: 1.247, 2-arc: 1.211, 3-arc: 1.211) except to single arc. D (Gy) of core for C-shape case was better for halcyon (1-arc: 23.29, 2-arc: 21.01, 3-arc: 20.64, 4-arc: 20.47) than for TB (1-arc: 24.04, 2-arc: 22.94, 3-arc: 23.04). Calculated MU was smaller for Halcyon than for TB. In addition, Halcyon is more faster than TB because mechanical movements were improved.
For VMAT plan in each case, Halcyon as well or better at the plan quality of two or three arcs on TB while reducing the delivery time.
直线加速器在机架、准直器、叶片和剂量率速度方面的新型改进可能会提高容积调强弧形治疗（VMAT）的时间效率，但仍有待研究。在本研究中，将具有快速移动叶片的快速旋转O型环直线加速器（Halcyon）与普通直线加速器（TrueBeam：TB）在AAPM TG - 119的C形、前列腺、多靶区以及头颈部（H&N）病例的VMAT计划质量方面进行了比较。
对于这四个测试病例，在Halcyon上使用单弧到四弧VMAT进行VMAT计划，在TrueBeam上使用单弧到三弧VMAT进行VMAT计划。每个测试病例使用相同的优化条件。比较了靶区覆盖指标和危及器官（OAR）剂量。还比较了每个计划中的监测单位（MU）和照射时间。
在所有病例中，Halcyon的单弧计划在剂量目标方面不如TB计划。除单弧外，Halcyon对C形病例外部靶区的适形指数（CI）（1弧：1.242，2弧：1.202，3弧：1.198，4弧：1.181）比TB（1弧：1.247，2弧：1.211，3弧：1.211）更好。Halcyon对C形病例核心区域的D（Gy）（1弧：23.29，2弧：21.01，3弧：20.64，4弧：20.47）比TB（1弧：24.04，2弧：22.94，3弧：23.04）更好。Halcyon计算出的MU比TB小。此外，由于机械运动得到改善，Halcyon比TB更快。
对于每种情况下的VMAT计划，Halcyon在TB两弧或三弧的计划质量方面与之相当或更好，同时减少了照射时间。
