容积旋转调强与固定野动态调强在上段食管癌治疗中的剂量学比较

Dosimetric comparison between Rapid Arc and fixed gantry dynamic IMRT for upper esophageal cancer

目的比较容积旋转调强(VMAT)与固定野动态调强(dIMRT)在上段食管癌放疗计划中的剂量学差异。方法利用瓦里安Eclipse 8.6计划系统对10例上段食管癌患者分别设计单弧360°Rapid Arc放疗计划和五野均分的dIMRT放疗计划。利用剂量体积直方图(DVH)来统计GTV和PTV的相关剂量参数、适形指数(CI)、均匀性指数(HI),肺、脊髓、正常组织的剂量体积参数,以及总机器跳数(MU)、总治疗时间。结果 Rapid Arc与dIMRT计划中GTV的D2、D98、HI、CI和V100差异均有统计学意义(P<0.05),PTV的D2、HI、CI差异均有统计学意义(P<0.05),Rapid Arc计划的GTV和PTV更具优势;Rapid Arc和dIMRT脊髓D1分别为(3644.15±72.89)cGy和(3810.69±97.51)cGy(P<0.05),肺V20为(13.65±2.19)%和(15.14±1.24)%(P>0.05),平均剂量为(893.95±102.43)cGy和(882.86±120.67)cGy(P>0.05);Rapid Arc计划与dIM-RT计划MU分别为482±36和763±89,治疗时间为(102±19)s和(336±41)s。结论 Rapid Arc计划可以达到或优于dIM-RT计划的靶区剂量分布,具有较少MU和总治疗时间的优势,能够更好地降低危及器官的受照剂量,可以获得更好的靶区剂量均匀性和靶区适合度。

Objective To compare the dosimetric difference between Rapid Arc and fixed gantry dynamic intensity modulated radiation therapy（IMRT） for upper esophageal cancer. Methods For ten cervical esophageal cancer cases, dlMRT plan（ five fixed- fields） and Rapid Arc plan were generated by Varian Eclipse 8.6 treatment planning systerm. Dose volume histograms were adopted for the statistics of D2 , D98 , conformal index（ CI）, homogeneity index（HI） of GTV and PTV, dose volumetric parameters of normal tis- sues ,lung and spinal cord, total accelerator output monitor units and total treatment time. Results When Rapid Arc compared to dIM- RT, there were significant differences in D2, D9s, Vl00, CI and HI of GTV （P 〈 0. 05 ） , and there were only significant differences in D2, CI and HI of PTV（P 〈0.05）. Rapid Arc had more advantages in GTV and PTV. The D1 of spinal cord was（3644. 15 ±72. 89） cGy for Rapid Arc and （ 3810. 69 ± 97.51 ） cGy for dIMRT （ P 〈 0. 05 ）. The V20 and mean close of lung were （ 13.65 ± 2. 19 ） % , （ 893.95± 102.43 ） eGy for Rapid Arc and （ 15. 14 ± 1.24 ） %, （ 882. 86 ± 120. 67 ） cGy for dIMRT（ P 〉 0. 05 ）. The number of monitor units were 482 ± 36 and 763 ± 89 in Rapid Arc and dlMRT ; the treatment time were （ 102 ± 19 ） s and （ 336 ± 41 ） s. Conclusion Compared to the dIMRT, Rapid Arc showes similar or better effects in the target dose distribution, it has the advantages in less monitor units and less total treatment time, it reduces the irradiation doses on oragans at risk better. Moreover, it gets better HI and CI.