Objective To evaluate the effects on bladder and rectum by high-dose-rate interstitial brachythe-rapy with CT-based 3D planning and the routine brachytherapy plan.Methords 25 cases of cervical cancer were chosen randomly to design the CT image-based interstitial brachytherapy plan.In contrast,the rou-tine brachytherapy plan was made for 20 cases.The prescribed dose was 28Gy/4f with high-dose-rate intra-cavitary irradiation and DVH was adopted to evaluate bladder wall dose,rectum wall dose and clinical tar-get volume.Results There were obvious differences of bladder wall dose and rectal wall dose in CT image-based interstitial brachytherapy plan and the routine brachytherapy plan.The mean dose,0.1 cm3 ,1 cm3 , 2 cm3 ,5 cm3 ,and 10 cm3 of bladder wall was 62.82,55.20,51.85,46.01 and 40.26 Gy respectively in the trial group with tumor diameter <4 cm.0.1 cm3 ,1 cm3 ,2 cm3 ,5 cm3 and 10 cm3 of bladder wall was 66.63,58.49,54.70,48.26 and 41.82 Gy respectively in the trial group with tumor diameter ≥4 cm.The mean dose,0.1 cm3 ,1 cm3 ,2 cm3 ,5 cm3 and 10 cm3 of rectal wall was 59.98,52.96,48.63,40.20 and 30.74 Gy respectively in the trial group with Tumor diameter <4 cm.0.1 cm3 ,1 cm3 ,2 cm3 ,5 cm3 and 10 cm3 of rectal wall was 59.74,46.64,41.38,32.75 and 21.98 Gy respectively in the trial group with Tumor diameter ≥4 cm.The mean dose,0.1 cm3 ,1 cm3 ,2 cm3 ,5 cm3 and 10 cm3 of bladder wall was 70.24,66.58,60.64,53.49 and 46.36 Gy respectively in the comparison group with Tumor diameter<4 cm.0.1 cm3 ,1 cm3 ,2 cm3 ,5 cm3 and 10 cm3 of bladder wall was 107.24,86.45,79.15,66.82 and 55.39 Gy respectively in the comparison group with tumor diameter ≥4 cm.The mean dose,0.1 cm3, 1 cm3 ,2 cm3 ,5 cm3 and 10 cm3 of rectal wall was 58.74,49.12,45.59,39.53 and 32.85 Gy respectively in the comparison group with tumor diameter<4 cm.0.1 cm3 ,1 cm3 ,2 cm3 ,5 cm3 and 10 cm3 of rectal wall was 63.90,58.02,55.20,50.23 and 44.14 Gy respectively in the comparison group with tumor diameter≥4 cm.Conclusion The doses of bladder wall and rectal wall were lower with the CT image-based inter-stitial brachytherapy plan,which decreased the complication of bladder and rectum and unnecessary inj ury as well.%目的：探讨CT引导的三维插植腔内高剂量率后装放疗（HDR-ISBT）在宫颈癌治疗中对膀胱、直肠的影响。方法随机选取25例中晚期宫颈癌病例为试验组，设计第一程行体外盆腹腔三维适形调强放疗（IMRT）照射计划，处方剂量45～50 Gy，共18～25次，在完成处方剂量20～30 Gy后加入CT引导的三维插植腔内高剂量率后装放疗。另20例加入常规单管后装放疗计划为对照组，利用体积剂量直方图（DVH）分别评价膀胱壁、直肠壁的受照剂量，比较两组间膀胱壁、直肠壁受照剂量的差别。结果（1）CT引导的高剂量率三维插植腔内后装治疗计划中，膀胱壁的平均剂量在肿瘤直径＜4 cm时，0．1、1、2、5 cm3和10 cm3分别为62．82、55．20、51．85、46．01 Gy和40．26 Gy；在肿瘤直径≥4 cm时，0．1、1、2、5 cm3和10 cm3分别为66．63、58．49、54．70、48．26 Gy和41．82 Gy。直肠壁平均剂量在肿瘤直径＜4 cm时，0．1、1、2、5 cm3和10 cm3分别为59．98、52．96、48．63、40．20 Gy和30．74 Gy；在肿瘤直径≥4 cm时，0．1、1、2、5 cm3和10 cm3分别为59．74、46．64、41．38、32．75 Gy和21．98 Gy。（2）常规后装膀胱壁平均剂量在肿瘤直径＜4 cm时，0．1、1、2、5 cm3和10 cm3分别为70．24、66．58、60．64、53．49 Gy和46．36 Gy；在肿瘤直径≥4 cm时，0．1、1、2、5 cm3和10 cm3分别为107．24、86．45、79．15、66．82 Gy和55．39 Gy。常规后装直肠壁的平均剂量在肿瘤直径＜4 cm时0．1、1、2、5 cm3和10 cm3分别为58．74、49．12、45．59、39．53 Gy和32．85 Gy；在肿瘤直径≥4 cm时，0．1、1、2、5 cm3和10 cm3分别为63．90、58．02、55．20、50．23 Gy和44．14 Gy。在肿瘤直径＜4 cm或≥4 cm时，两组膀胱壁及直肠壁受照剂量差异均有统计学意义（P ＜0．05）。结论在宫颈癌 CT引导的三维插植腔内后装计划设计中，膀胱壁、直肠壁受照剂量明显低于常规后装放疗。对膀胱、直肠损伤减少，从而可能降低膀胱、直肠并发症发生概率。
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