Department of Radiation Oncology, Osaka International Cancer Institute, 3-1-69 Otemae, Chuo-ku, Osaka, 537-8567, Japan.
Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, 1-7 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Radiat Oncol. 2018 Jan 29;13(1):13. doi: 10.1186/s13014-017-0948-z.
The HyperArc VMAT (HA-VMAT) planning approach was newly developed to fulfill the demands of dose delivery for brain metastases stereotactic radiosurgery. We compared the dosimetric parameters of the HA-VMAT plan with those of the conventional VMAT (C-VMAT).
For 23 patients (1-4 brain metastases), C-VMAT and HA-VMAT plans with a prescription dose of 20-24 Gy were retrospectively generated, and dosimetric parameters for PTV (homogeneity index, HI; conformity index, CI; gradient index, GI) and brain tissue (V-V) were evaluated. Subsequently, the physical characteristics (modulation complexity score for VMAT, MCSV; Monitor unit, MU) of both treatment approaches were compared.
HA-VMAT provided higher HI (1.41 ± 0.07 vs. 1.24 ± 0.07, p < 0.01), CI (0.93 ± 0.02 vs. 0.90 ± 0.05, p = 0.01) and lower GI (3.06 ± 0.42 vs. 3.91 ± 0.55, p < 0.01) values. Moderate-to-low dose spreads (V-V) were significantly reduced (p < 0.01) in the HA-VMAT plan over that of C-VMAT. HA-VMAT plans resulted in more complex MLC patterns (lower MCSV, p < 0.01) and higher MU (p < 0.01).
HA-VMAT plans provided significantly higher conformity and rapid dose falloff with respect to the C-VMAT plans.
新开发的 HyperArcVMAT（HA-VMAT）计划方法旨在满足脑转移立体定向放射外科的剂量传递要求。我们比较了 HA-VMAT 计划和传统 VMAT（C-VMAT）的剂量学参数。
回顾性地为 23 名患者（1-4 个脑转移灶）生成了 C-VMAT 和 HA-VMAT 计划，处方剂量为 20-24Gy，并评估了 PTV（均匀性指数、HI；适形指数、CI；梯度指数、GI）和脑组织（V-V）的剂量学参数。随后，比较了两种治疗方法的物理特性（VMAT 的调制复杂度评分、MCSV；监测单位、MU）。
HA-VMAT 提供了更高的 HI（1.41±0.07 对 1.24±0.07，p<0.01）、CI（0.93±0.02 对 0.90±0.05，p=0.01）和更低的 GI（3.06±0.42 对 3.91±0.55，p<0.01）值。HA-VMAT 计划中的中低剂量分布（V-V）明显减少（p<0.01）。HA-VMAT 计划导致更复杂的 MLC 模式（较低的 MCSV，p<0.01）和更高的 MU（p<0.01）。
HA-VMAT 计划在 C-VMAT 计划的基础上提供了更高的一致性和更快的剂量衰减。
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