宫腔管深度对膀胱直肠剂量的影响

The Effect of Tandem Depth on Bladder and Rectum Dose

目的:探讨宫颈癌根治性放射治疗患者用A点作为剂量参考点的后装中,宫腔管深度对膀胱直肠剂量的影响。方法:选取宫颈癌根治性放射治疗患者23例,宫体深度均大于6cm,处方剂量A点6Gy,通过改变源驻留点个数,模拟计算同一患者宫腔管深度在6cm、5cm、4cm、3cm时膀胱直肠的D2cc和D50,以6cm膀胱直肠数据为基准,对比分析宫腔管深度对膀胱直肠剂量的影响。结果:膀胱直肠的D2cc随宫腔管深度的增加而减小,与宫腔管深度在6cm相比,5cm、4cm、3cm时膀胱的平均值分别增加7c Gy、22c Gy、63c Gy(P=0.000),直肠的平均值分别增加13c Gy、37c Gy、93c Gy(P=0.000)。膀胱直肠的D50在宫腔管深度6cm、5cm、4cm时变化不大,膀胱的平均值分别为(227±33)c Gy、(226±34)c Gy、(228±34)c Gy,直肠的平均值分别为(182±28)c Gy、(181±28)c Gy、(184±27)c Gy,差异无统计学意义(P>0.05)。宫腔管深度在3cm深度时膀胱直肠的D50较6cm、5cm、4cm明显增加,膀胱平均值为(239±35)c Gy(P=0.001),直肠的平均值为(195±29)c Gy(P=0.000),差异有统计学意义。结论:对根治性放射治疗宫颈癌患者,用传统的A点作为剂量参考点,在保证宫腔管不穿出宫体的前提下增加宫腔管深度可以降低膀胱和直肠的剂量,这对于降低宫颈癌患者放疗并发症有重要意义。

Objective： To quantify the effects of tandem depth on bladder and rectum dose in conventional cervical cancer brachytherapy which used point A as dose reference point. Methods： Twenty three patients with cervical cancer whose depth of uterus was greater than 6cm were included in this study. The prescription dose was 6Gy to point A. 6cm,5cm,4cm,3cm of tandem depth were simulated in patients by changing the dwell source number. D2 ccand D50for bladder and rectum were calculated by treatment planning system. 6cm data of bladder and rectum was selected as a benchmark to compare and analyze the tandem depth effects on bladder and rectum dose. Results： The D2 ccof bladder and rectum decreased with the increase of tandem depth. Compared with 6cm,the mean value of bladder increased 7c Gy,22 c Gy,63 c Gy,P = 0. 000,the mean value of rectum increased 13 c Gy,37 c Gy,93 c Gy,P = 0. 000 in the case when 5cm,4cm,3cm tandem depth were adopted respectively. The changes of bladder and rectum D50 in 6cm,5cm,4cm were small,the average value of bladder were（ 227 ± 33） c Gy,（ 226 ± 34） c Gy,（ 228 ± 34） c Gy,the average value of rectum were（ 182 ±28） c Gy,（ 181 ± 28） c Gy,（ 184 ± 27） c Gy,with no statistical difference. When the tandem depth decreased to 3cm,the D50 of bladder and rectum increased significantly with the average value of bladder was（ 239 ± 35） c Gy（ P = 0. 001）,the average value of rectum was（ 195 ± 29） c Gy（ P = 0. 000）. Conclusion： For cervical cancer patients who accepting brachytherapy which use point A as dose reference point,increasing tandem depth can reduce bladder and rectum dose and of great significance for reducing the complications of patients under the guarantee that tandem do not wear out from uterine.