宫颈癌图像引导下调强放疗中危及器官变化对靶区的影响

Effect of changes in organs at risk on target volume during image-guided radiation therapy for cervical cancer

目的探讨晚期宫颈癌患者调强放疗中危及器官体积及位置变化对靶区的影响。方法选取行图像引导下调强放疗宫颈癌患者16例,分别于放疗剂量达9 Gy/5f、18 Gy/10f、27 Gy/15f、36 Gy/20f及48.6 Gy/27f时用锥束CT(CBCT)扫描,采集CBCT图像,与原始治疗计划CT图像配准,分别在CT和CBCT图像中勾画大体肿瘤靶区及危及器官,比较危及器官体积、体积变化率及DICE相似度指数(dice's similarity coefficient,DSC)。结果放疗0~27分次膀胱、直肠、乙状结肠与小肠体积范围分别为88.48~195.49 cm^3、40.41~42.93 cm^3、792.85~907.86 cm^3、38.49~49.05 cm^3。膀胱0~27分次体积变化差异有统计学意义(P=0.002),其余器官体积变化差异无统计学意义(P>0.05)。膀胱、直肠、乙状结肠及小肠0~27分次体积变化率和DSC差异均无统计学意义(P>0.05)。膀胱、直肠体积变化率与宫颈靶区、宫体的DSC均呈负相关(P<0.05)。结论宫颈癌调强放疗中膀胱、直肠等体积与位置变化较大,其变化可能影响宫颈靶区、子宫体的空间位置。

Objective To investigate the effect of changes in volume and position of the bladder and rectum on target volume in patients with advanced cervical cancer using intensity-modulated radiotherapy. Methods A total of 16 cases of intensity-modulated radiotherapy in patients with cervical cancer were analyzed,and CBCT imaging was performed at radiotherapy doses of 9 Gy/5f, 18 Gy/10f,27 Gy/15f,36 Gy/20f and 48.6 Gy/27f. CBCT images were integrated with the original CT image,and the target volume and organs at risk （OARs） were outlined. Dose volume histograms （DVH） were used to analyze changes in volume,volume change rate and DICE similarity of rectum,bladder and other organs. Results Mean volume of bladder was 88.48-195.49 cm3;rectum,40.41-42.93 cm3;sigmoid, 792.85-907.86 em3;and intestine,38.49-49.05 cm3. Bladder volume varied significantly from Of to 27 f （P〈0.05）,but the other organs did not differ significantly in volume change rate（ delta V%, P〉0.05 ） and in DICE similarity （DSC ,P〉0.05 ）. Bladder volume rate and rectal volume showed a significant negative correlation with the DSC of the gross tat＇get volume （GTV-T） and the corpus （CTV-T） （P〈0.05）. Condusions Volume and location of the bladder,rectum and other organs changed substantially during intensity-modulated radiation therapy of cervical cancer. Volume change rate of bladder and rectum negatively correlated with the DSC of GTV-T and CTV-T.