Objective To discuss the feasibility of CBCT (Cone Beam Computerized Tomography) in detecting the volume change of the bladder and cervical target in image-guided radiotherapy for cervical cancers. Methods Ten cervical cancer patients were selected and asked to keep their bladders full. Then, the outline of bladders and cervical targets was made in the CT simulation and CBCT images which were obtained in the same window width and position. The volume of the bladder and cervical targets was calculated by the Varian Planning System so as to compare the volume changes in each radiation as well as the relative volume changes (the proportion of the contoured organ volume in CBCT to that in CT) in bladders and cervical targets. Results The volume of the bladder and cervical targets acquired by CBCT in all the patients varied from time to time and from patient to patient. The volume changes of bladders were between-35.15%and+16.24%;while the volume changes of cervical targets ranged from+21.26%to-76%. The maximum, minimum and mean relative volume of bladders was 1.5, 0.65 and 0.96 respectively. With the increase in the radiotherapy, the volume of cervical targets obtained by CBCT reduced, especially in the 4th and 5th weeks. Conclusion Cone beam CT can be used to detect the volume changes of bladders and cervical targets in radiotherapy for cervical cancers, which provided a basis for clinicians to modify the radiotherapy plan.%目的：探讨锥形束CT（CBCT）在宫颈癌图像引导放疗中监测膀胱和宫颈靶区体积变化的可行性。方法选取10例宫颈癌患者，要求患者膀胱自主充盈，在相同窗宽和窗位下，于模拟定位CT和CBCT图像上勾画膀胱和宫颈靶区，利用Varian治疗计划系统计算膀胱和宫颈靶区的体积，比较各体积随放疗次数的变化趋势，并比较膀胱和宫颈靶区的相对体积（基于CBCT勾画的器官体积与基于CT勾画的器官体积之比）变化。结果每例患者每次进行CBCT扫描后获得的膀胱体积和宫颈靶区体积均有所不同，膀胱体积最大增加16.24%，最大减少35.15%；宫颈靶区体积最大增加21.26%，最大减少76%。膀胱相对体积最大为1.5，最小为0.65，均值为0.96。随放疗次数增加，基于CBCT勾画的宫颈靶区体积逐渐缩小，呈下降趋势，第四和第五周体积明显减小。结论锥形束CT可以监测宫颈癌放疗中膀胱和宫颈靶区的体积变化，为放疗计划修改提供依据。
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