锥形束CT在宫颈癌放疗中的应用

Application of cone beam CT in cervical cancer

目的:研究宫颈癌患者在图像引导放疗中膀胱和宫颈靶区体积的变化规律。方法:患者膀胱自主充盈,在相同窗宽窗位下,分别在模拟定位CT和锥形束CT(CBCT)图像上勾画膀胱和宫颈外轮廓,利用计划系统分次计算膀胱和宫颈体积(Vb-ct,Vb-cbct,Vc-ct,Vc-cbct);比较其体积变化与放疗时间的关系。结果:在CBCT图像和模拟CT上勾画的膀胱体积和宫颈区域体积有所不同,膀胱体积增加和减少的百分比最大、最小值分别为16.24%、0.94%,-35.15%、-8.87%;而宫颈区域体积增加和减少的百分比最大、最小值分别为21.26%、-13.5%,-76%、-37.41%。膀胱相对体积最大、最小值和均值分别为1.5、0.65、0.96;而宫颈区域相对体积最大、最小值和均值分别为1.2、0.24、0.76。放疗5周后宫颈区域相对体积均值分别为0.97、0.91、0.78、0.62、0.50。宫颈靶区体积随放疗进行逐渐缩小,后2周较显著。结论:图像引导放疗可以保证宫颈癌放疗的精度;对靶区在线监测,及时修改放疗计划可以实现宫颈癌的自适应放疗。

Objective To study the changes of target volumes of the bladder and cervix in image-guided radiotherapy.Methods With the bladder self filled and the width and position fixed, the contours of the bladder and cervix were sketched out in the simulated positioning CT and CBCT images, and the volumes of the bladder and cervix were calculated in turn for Vb-ct, Vb-cbct, Vc-ctand Vc-cbctwith the planning system, then the relationships between the volume changes and radiotherapy time were compared. Results The bladder and cervix volumes sketched in CBCT images were different with those in simulated CT images. The maximum percentage and minimum one for the increased and decreased bladder volumes were 16.24%, 0.94%,-35.15% and-8.87% respectively, and those for the increased and decreased cervix volumes were 21.26%,-13.5%,-76% and-37.41% respectively. The maximum, minimum and mean values of the relative volumes of the bladder were 1.5, 0.65 and 0.96 respectively, those of the cervix were 1.2, 0.24 and 0.76 respectively, and the mean values of the relative volume of the cervix after 5-week radiotherapy were 0.97, 0.91, 0.78,0.62 and 0.50 respectively. The target volume of the cervix decreased with the radiotherapy, especially two weeks after.Conclusion Image-guided radiotherapy can ensure the treatment precision of the cervical cancer, and target area online monitoring and modifying plan in time may realize self-adaptive radiotherapy for it.