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目的:比较贲门癌术后不同靶区照射方式的剂量分布及对正常组织受量的影响。方法:选取2011-07-01-2012-10-31在安徽医科大学第一附属医院放疗科行贲门癌根治术的患者10例,均需行术后辅助放疗。每名患者制定A、B两种放疗计划。A计划定义为包含3~5cm的食管、术后瘤床及区域淋巴结的单一靶区照射;B计划定义为“3~5cm的食管”和“术后瘤床及区域淋巴结”2个靶区照射。规定计划靶体积(planning target volume,PTV)接受≥95%处方剂量(45Gy)。利用剂量体积直方图(dose volume histogram,DVH)比较A、B计划V45、V42.75(靶区接受45和42.75Gy照射体积占整个体积的比例)、适形指数(conformal index,CI)、剂量均匀性指数(heterogeneity index,HI)、外部体积指数(external volume index,EI)及肺脏、肝脏、肾脏和脊髓的受量。结果:A计划剂量参数V45为(96.345±0.857 1)%,V42.75为(99.452±0.185 4)%,HI为0.989 1±0.056 1,EI为0.174 8±0.343 9;B计划剂量参数V45为(96.059±0.392 9)%,V42.75为(99.518±0.166 5)%,HI为0.998 7±0.224 0,EI为0.210 4±0.064 1,两种计划参数相比差异均无统计学意义,P>0.05。但B计划的CI(0.813 1±0.074 4)较A计划CI(0.938 6±0.046 2)具有明显优势,P<0.001。B计划正常组织受量参数,左肺平均剂量(Dmean)为(511.204±151.879)Gy,右肺Dmean为(517.996±90.470 1)Gy,肝脏Dmean为(2 030.034±292.746)Gy,脊髓最高剂量(Dmax)为(32.269±4.133 6)Gy,左肾V15为(86.586±6.806 8)%,左肾V23为(60.790±10.158 4)%,明显优于A计划的(638.467±140.934 5)Gy、(618.550±110.776 1)Gy、(2251.763±284.493)Gy、(36.561±2.245 4)Gy、(96.785±1.658 6)%和(67.316±8.340 6)%,差异有统计学意义,P值均<0.05;而两种计划的右肾V15(P=0.712)和V23(P=0.427)差异无统计学意义。结论:贲门癌术后采用两种放疗计划均能保证靶区的剂量理想分布;但是B计划的照射方式能有效降低肺脏、肝脏、肾脏及脊髓受照剂量,具有较明显的剂量学优势。
OBJECTIVE: To compare the dose distribution of different target irradiation modes and the influence on the normal tissue volume after cardiac cancer surgery. METHODS: A total of 10 patients undergoing cardia cancer radical resection at the Department of Radiotherapy at the First Affiliated Hospital of Anhui Medical University from 2011-07-01-2012-10-31 were selected for postoperative adjuvant radiotherapy. Each patient developed A and B radiotherapy plans. Plan A is defined as a single target area with 3 to 5 cm of esophagus, postoperative tumor bed, and regional lymph nodes; Plan B is defined as a “3 to 5 cm esophagus” and “postoperative tumor bed and regional lymph nodes.”2 Target area irradiation. The prescribed target volume (PTV) is expected to receive ≥95% of the prescribed dose (45 Gy). Using dose volume histogram (DVH) to compare A and B plans V45, V42.75 (target volume receiving 45 and 42.75 Gy irradiation volume as a proportion of the entire volume), conformal index (CI), dose Heterogeneity index (HI), external volume index (EI), and lung, liver, kidney, and spinal cord. RESULTS: The planned dose parameters V45 was (96.345±0.857 1)%, V42.75 was (99.452±0.185 4)%, HI was 0.989 1±0.056 1, and EI was 0.174 8±0.343 9. The planned dose parameter V45 was (96.059±0.392 9)%, V42.75 was (99.518±0.166 5)%, HI was 0.998 7±0.224 0, and EI was 0.210 4±0.064 1. There was no statistically significant difference between the two planning parameters. P >0.05. However, the CI of the B plan (0.813 1±0.074 4) was significantly superior to the A plan CI (0.938 6±0.046 2), P<0.001. In the B-planned normal tissue volumetric parameters, the average D median (Dmean) was (511.204±151.879) Gy. Dmean in the right lung was (517.996±90.470 1) Gy. The Dmean in the liver was (2 030.034±292.746) Gy. The maximum dose of spinal cord ( Dmax) was (32.269±4.133 6)Gy, left kidney V15 was (86.586±6.806 8)%, and left kidney V23 was (60.790±10.158 4)%, which was significantly better than that of A (638.467±140.934 5) Gy, ( 618.550±110.776 1) Gy, (2251.763±284.493)Gy, (36.561±2.245 4)Gy, (96.785±1.658 6)% and (67.316±8.340 6)%, the difference was statistically significant, P<0.05; There was no statistically significant difference between the two types of planned right kidney V15 (P=0.712) and V23 (P=0.427). Conclusion: Two radiotherapy plans for postoperative cardiac cancer can ensure ideal dose distribution in the target area; however, the radiation pattern in plan B can effectively reduce the radiation dose to the lung, liver, kidney and spinal cord, and has obvious dosimetric advantages.