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目的:比较旋转容积调强(VMAT)与固定野动态调强(dIMRT)在直肠癌放疗计划中的剂量学差异。方法:8例直肠癌患者利用瓦里安计划系统(Eclipse 8.6)分别进行VMAT和dIMRT放射治疗计划设计。利用剂量体积直方图来比较两种计划中靶区和危及器官的剂量学差异。结果:与dIMRT相比,VMAT靶区适合度指数(CI)、靶区剂量均匀性指数(HI)均更接近1,Dmin为(43.403±0.486)Gy,更接近处方剂量,差异有统计学意义,P<0.05。在VMAT计划中小肠的D30%、D50%和Dmean分别为(25.918±1.216)、(22.340±3.784)和(23.547±2.863)Gy,低于dIMRT计划的(28.073±3.114)、(24.172±2.540)和(25.257±1.374)Gy,P值分别为0.00、0.01和0.00;膀胱的D30%为(35.380±2.734)Gy,较dIMRT的(30.123±2.209)Gy偏高,P=0.00,但仍远低于剂量限值;股骨头的D5%和Dmean分别为(31.344±3.556)和(20.179±3.017)Gy,显著高于dIMRT计划的(26.731±2.828)和(17.459±3.279)Gy,P值均为0.00。VMAT总MU减少52.7%,治疗时间仅为dIMRT的1/4。结论:VMAT计划可以达到或优于dIMRT计划的靶区剂量分布,能更好地降低部分危及器官的受照剂量,并且具有较少总MU、总治疗时间的优势,减少了治疗中不确定性因素的影响及患者不适感。
OBJECTIVE: To compare the dosimetry differences between revascularization (VMAT) and fixed field dynamics (dIMRT) in radiotherapy of rectal cancer. METHODS: Eight patients with rectal cancer were enrolled in a Varian Plan System (Eclipse 8.6) for the design of a radiotherapy plan for VMAT and dIMRT respectively. Dose volume histograms were used to compare the dosimetry differences between the two planned targets and those at risk to the organ. Results: Compared with dIMRT, the fitness index (VM) of the VMAT target and the homogeneity index (HI) of the target region were all closer to 1, and the Dmin was (43.403 ± 0.486) Gy, which was closer to the prescription dose with a statistically significant difference , P <0.05. The D30%, D50% and Dmean of the small intestine in the VMAT plan were (25.918 ± 1.216), (22.340 ± 3.784) and (23.547 ± 2.863) Gy, respectively, which were lower than those of the dIMRT plan (28.073 ± 3.114) and (24.172 ± 2.540) And (25.257 ± 1.374) Gy respectively, with P values of 0.00, 0.01 and 0.00, respectively; Bladder D30% was (35.380 ± 2.734) Gy, higher than that of dIMRT (30.123 ± 2.209) Gy, P = 0.00 but still far lower D5% and Dmean of femoral head were (31.344 ± 3.556) and (20.179 ± 3.017) Gy, respectively, which were significantly higher than those of dIMRT (26.731 ± 2.828) and (17.459 ± 3.279) Gy, P values were 0.00. The total MUAT of VMAT decreased by 52.7% and the treatment time was only 1/4 of dIMRT. CONCLUSIONS: The VMAT program achieves or outperforms the dIMRT target dose distribution and is better able to reduce some of the organically compromised doses and has the advantage of less total MU, total duration of treatment, less uncertainty in treatment The impact of factors and patient discomfort.