Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan.
Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan.
Pract Radiat Oncol. 2017 Nov-Dec;7(6):382-387. doi: 10.1016/j.prro.2017.04.004. Epub 2017 Apr 13.
Reducing the radiation dose to the hippocampus is important to preserve cognitive function in patients with brain tumors. The Vero4DRT system can realize a new irradiation technique, termed volumetric-modulated Dynamic WaveArc therapy (VMDWAT), which allows the safe use of sequential noncoplanar volumetric-modulated beams without couch rotation. Because VMDWAT appears to reduce the hippocampal dose in patients with pituitary adenomas and craniopharyngiomas, we performed a planning study to compare the dose distribution of volumetric-modulated arc therapy using only a coplanar arc (coVMAT) and VMDWAT.
CoVMAT and VMDWAT plans were created for 30 patients with pituitary adenomas and craniopharyngiomas. The prescription dose was 52.2 Gy in 29 fractions, with 99% of each planning target volume covered by 90% of the prescribed dose. Optimization was performed for maximal reduction of the dose to the hippocampus. Treatment time was defined as the beam-on time.
The mean equivalent dose in 2 Gy fractions to 40% of the volume of the bilateral hippocampus (EQD40%) for coVMAT/VMDWAT were 9.90/5.31 Gy, respectively (P < .001). The mean EQD40% in VMDWAT was less than 7.3 Gy, which is the threshold for predicting cognitive impairment. Although the volume of normal brain receiving 5 Gy (V5) was significantly larger in VMDWAT, compared with coVMAT, the normal brain volume receiving 10, 15, 20, 25, 30, 35, 40, 45, and 50 Gy (V10-50) was significantly smaller in VMDWAT. The conformity and homogeneity indices were significantly better in VMDWAT. The mean VMDWAT treatment time was longer compared with coVMAT (70.1 vs 67.1 seconds, respectively).
Although VMDWAT increased brain V5 and the treatment time compared with coVMAT, it significantly reduced the dose to the hippocampus and brain V10 to V50 and improved target conformity and homogeneity. VMDWAT could be a promising treatment technique for pituitary adenomas and craniopharyngiomas.
降低海马体的放射剂量对于保护脑肿瘤患者的认知功能非常重要。Vero4DRT 系统可以实现一种新的照射技术，称为容积调制动态弧形治疗（VMDWAT），它允许安全地使用连续的非共面容积调制射线，而无需旋转治疗床。由于 VMDWAT 似乎降低了垂体腺瘤和颅咽管瘤患者的海马体剂量，我们进行了一项计划研究，比较了仅使用共面弧（coVMAT）和 VMDWAT 的容积调制弧形治疗的剂量分布。
为 30 名垂体腺瘤和颅咽管瘤患者创建了 coVMAT 和 VMDWAT 计划。处方剂量为 52.2Gy，共 29 个分次，每个计划靶区 99%的体积接受 90%的处方剂量。进行了优化以最大程度地降低海马体的剂量。治疗时间定义为射束开启时间。
coVMAT/VMDWAT 的双侧海马体 40%等剂量体积（EQD40%）的平均等效剂量分别为 9.90/5.31Gy（P<0.001）。VMDWAT 的平均 EQD40%低于 7.3Gy，这是预测认知障碍的阈值。尽管 VMDWAT 中接受 5Gy（V5）的正常脑组织体积明显大于 coVMAT，但 VMDWAT 中接受 10、15、20、25、30、35、40、45 和 50Gy（V10-50）的正常脑组织体积明显小于 coVMAT。VMDWAT 的适形度和均匀性指数明显更好。VMDWAT 的平均治疗时间长于 coVMAT（分别为 70.1 秒和 67.1 秒）。
尽管 VMDWAT 与 coVMAT 相比增加了脑 V5 和治疗时间，但它显著降低了海马体和脑 V10 到 V50 的剂量，并改善了靶区的适形度和均匀性。VMDWAT 可能是治疗垂体腺瘤和颅咽管瘤的一种有前途的治疗技术。
