胸上段食管癌容积旋转调强和静态调强与三维适形放疗计划的剂量学比较

Volumetric Modulated Arc Therapy,Conventional Intensity-modulated Radiotherapy and Three-Dimensional Conformal Techniques for Upper Thoracic Esophageal Cancer: A Planning Comparison Study

【目的】比较容积旋转调强(VMAT)、静态调强(sIMRT)与三维适形放疗(3DCRT)技术在胸上段食管癌的剂量学差异。【方法】选取7例局部晚期胸上段食管癌患者,分别制定3DCRT、7野sIMRT和360度单弧VMAT 3套放疗计划,处方剂量统一为60 Gy/30F。比较靶区、危及器官的剂量体积参数,加速器的总机器跳数(MU)和有效治疗时间(TT)等。【结果】VMAT与IMRT的靶区剂量分布基本一致,均优于3DCRT。对于正常组织,三组计划中肺、心脏的受照剂量均无明显差异,但IMRT与VMAT可较3DCRT更好的保护脊髓。3DCRT、IMRT、VMAT的MU分别为537±92、601±122、682±139,有效治疗时间(min)分别为3.9±0.3、6.0±0.7、4.7±0.7(P<0.05)。【结论】与3DCRT相比,VMAT与IMRT在胸上段食管癌均有一定的剂量学优势,但VMAT较IMRT可显著提高治疗效率。

【Objective】 A planning study was performed to compare volumetric modulated arc therapy（VMAT）,static intensity-modulated radiotherapy（sIMRT）,and three-dimensional conformal radiotherapy（3DCRT） for upper thoracic esophageal cancer.【Methods】 Seven patients with loco-regionally advanced upper thoracic esophageal cancer were included.Based on the identical CT and planning target volume（PTV）,three plans（3DCRT,sIMRT with seven fields,VMAT with a single arc） were generated.Dose prescription was set to 60Gy in 30 fractions.Dose volume histograms,MU and delivery time were evaluated to assess plan quality.【Results】 In comparison to 3DCRT,both VMAT and IMRT provided a systematic improvement in PTV coverage.For normal tissues,equivalent sparing of lung and heart were achieved with three plans.However,IMRT and VMAT showed a superior sparing compared with 3DCRT for spinal cord.The MU/fraction was as follows： 537 ± 92 for 3DCRT,601 ± 122 for IMRT,and 682 ± 139 for VMAT.Effective treatment time for 3DCRT,IMRT and VMAT were（3.9 ± 0.3） min,（6.0 ± 0.7） min and（4.7 ± 0.7）min,respectively（P 0.05）.【Conclusions】 Compared with 3DCRT,IMRT and VMAT showed better dosimetric quality and superior spinal cord sparing.However,VMAT improved delivery efficiency significantly than IMRT.