1 Department of Radiation Oncology, Peking University Third Hospital, Beijing, China.
2 Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, NY, USA.
Technol Cancer Res Treat. 2019 Jan 1;18:1533033819871621. doi: 10.1177/1533033819871621.
To compare plan quality and delivery efficiency of noncoplanar volumetric modulated arc therapy with coplanar volumetric modulated arc therapy, intensity-modulated radiation therapy, and CyberKnife for multiple brain metastases.
For 15 patients with multiple brain metastases, noncoplanar volumetric modulated arc therapy, coplanar volumetric modulated arc therapy, intensity-modulated radiation therapy, and CyberKnife plans with a prescription dose of 30 Gy in 3 fractions were generated. Noncoplanar volumetric modulated arc therapy and coplanar volumetric modulated arc therapy plans consisted of 4 noncoplanar arcs and 2 full coplanar arcs, respectively. Intensity-modulated radiation therapy plans consisted of 7 coplanar fields. CyberKnife plans used skull tracking to ensure accurate position. All plans were generated to cover 95% target volume with prescription dose. Gradient index, conformity index, normal brain tissue volume ( - ), monitor units, and beam on time were evaluated.
Gradient index was the lowest for CyberKnife (3.49 ± 0.65), followed by noncoplanar volumetric modulated arc therapy (4.21 ± 1.38), coplanar volumetric modulated arc therapy (4.87 ± 1.35), and intensity-modulated radiation therapy (5.36 ± 1.98). Conformity index was the largest for noncoplanar volumetric modulated arc therapy (0.87 ± 0.03), followed by coplanar volumetric modulated arc therapy (0.86 ± 0.04), CyberKnife (0.86 ± 0.07), and intensity-modulated radiation therapy (0.85 ± 0.05). Normal brain tissue volume at high-to-moderate dose spreads ( - ) was significantly reduced in noncoplanar volumetric modulated arc therapy over that of intensity-modulated radiation therapy and coplanar volumetric modulated arc therapy. Normal brain tissue volume for noncoplanar volumetric modulated arc therapy was comparable with noncoplanar volumetric modulated arc therapy at high-dose level ( - ) and larger than CyberKnife at moderate-to-low dose level ( - ). Monitor units was highest for CyberKnife (28 733.59 ± 7197.85), followed by intensity-modulated radiation therapy (4128.40 ± 1185.38), noncoplanar volumetric modulated arc therapy (3105.20 ± 371.23), and coplanar volumetric modulated arc therapy (2997.27 ± 446.84). Beam on time was longest for CyberKnife (30.25 ± 7.32 minutes), followed by intensity-modulated radiation therapy (2.95 ± 0.85 minutes), noncoplanar volumetric modulated arc therapy (2.61 ± 0.07 minutes), and coplanar volumetric modulated arc therapy (2.30 ± 0.23 minutes).
For brain metastases far away from organs-at-risk, noncoplanar volumetric modulated arc therapy generated more rapid dose falloff and higher conformity compared to intensity-modulated radiation therapy and coplanar volumetric modulated arc therapy. Noncoplanar volumetric modulated arc therapy provided a comparable dose falloff with CyberKnife at high-dose level and a slower dose falloff than CyberKnife at moderate-to-low dose level. Noncoplanar volumetric modulated arc therapy plans had less monitor units and shorter beam on time than CyberKnife plans.
比较非共面容积旋转调强放疗（VMAT）、共面容积旋转调强放疗（VMAT）、调强放疗（IMRT）和 CyberKnife 治疗多发脑转移瘤的计划质量和治疗效率。
对 15 例多发脑转移瘤患者，分别制定处方剂量为 30Gy/3 次的非共面 VMAT、共面 VMAT、IMRT 和 CyberKnife 计划。非共面 VMAT 和共面 VMAT 计划分别由 4 个非共面弧和 2 个全共面弧组成。IMRT 计划由 7 个共面野组成。CyberKnife 计划使用颅骨追踪以确保精确的位置。所有计划均生成 95%的目标体积处方剂量。评估梯度指数、适形度指数、正常脑组织体积（ - ）、监测单位和射束开启时间。
CyberKnife 的梯度指数最低（3.49 ± 0.65），其次是非共面 VMAT（4.21 ± 1.38）、共面 VMAT（4.87 ± 1.35）和 IMRT（5.36 ± 1.98）。非共面 VMAT 的适形度指数最大（0.87 ± 0.03），其次是共面 VMAT（0.86 ± 0.04）、CyberKnife（0.86 ± 0.07）和 IMRT（0.85 ± 0.05）。非共面 VMAT 计划在高-中剂量区的正常脑组织体积（ - ）明显低于 IMRT 和共面 VMAT。非共面 VMAT 计划的正常脑组织体积在高剂量区（ - ）与非共面 VMAT 相当，在中-低剂量区（ - ）大于 CyberKnife。监测单位以 CyberKnife 最高（28733.59 ± 7197.85），其次是 IMRT（4128.40 ± 1185.38）、非共面 VMAT（3105.20 ± 371.23）和共面 VMAT（2997.27 ± 446.84）。CyberKnife 的射束开启时间最长（30.25 ± 7.32 分钟），其次是 IMRT（2.95 ± 0.85 分钟）、非共面 VMAT（2.61 ± 0.07 分钟）和共面 VMAT（2.30 ± 0.23 分钟）。
对于远离危及器官的脑转移瘤，非共面 VMAT 与 IMRT 和共面 VMAT 相比，能更快地产生剂量衰减和更高的适形度。非共面 VMAT 提供了与 CyberKnife 相当的剂量衰减在高剂量区，比 CyberKnife 低中剂量区的剂量衰减慢。非共面 VMAT 计划的监测单位和射束开启时间均少于 CyberKnife 计划。
