螺旋断层放疗自适应技术的初步应用

目的：通过比较螺旋断层自适应计划与非自适应计划中危及器官的受照剂量体积,评估应用螺旋断层放疗减少周围正常组织受照体积的临床可行性。方法与材料：收集5例患者治疗过程中每完成5个分次剂量后在螺旋断层治疗机上采集的兆伏级CT（MVCT）图像并勾画肿瘤范围（GTV）并测量GTV的体积,评价GTV的体积变化。完成20个分次照射剂量后应用MVCT图像勾画缩减后的GTV并创建自适应计划,通过比较自适应计划与非自适应计划危及器官的体积剂量直方图（DVH）,评估自适应放疗的剂量学优势。结果：5例应用螺旋断层放疗自适应技术的病人的GTV在完成25个治疗分次后与治疗前比较均有明显的缩小（约为40%～60%）。三例肺癌患者接受20 Gy照射的同侧肺的体积平均减少了8.76%;两例盆腔患者接受40 Gy照射的小肠体积减少了1.48%;接受40 Gy照射的直肠体积减少了8.86%;接受45 Gy照射的膀胱体积减少了7.67%。而应用螺旋断层放疗系统实施自适应放疗技术平均只需要185.4min。结论：应用螺旋断层放疗的自适应技术减少周围正常组织的受照体积在临床上是可行的。

A Preliminary Application of the Helical Tomotherapy Adaptive System

Objective: We evaluated the possibility of using adaptive technology to reducing the irradiation of surrounding normal tissue by comparing the irradiation volume of the surrounding organs at risk(OAR) in both adaptive and non-adaptive scheme.Methods: MVCT images every five fractionated doses in 5 patients were collected to measure Gross Tumor Volume(GTV).The change of GTV volume was investigated.The advantage of Adaptive plan was evaluated by comparing the DVH between the Adaptive plan s and non-adaptive plan post 25 fractionated dose using MVCT image.Results: GTV of the five patients receiveing 25 faction radiotherapy were obviously reduced(about 40%～60%).The mean ipsilateral lung volume of three patients with lung cancer was reduced 8.76% after received 20 Gy irradiation;For the two patients with pelvic tumour,their small bowel volumes and rectal volumes after receiving 40 Gy irradiation were reduced by 1.48% and 8.86%,respectively,and their bladder volumes after receiving 45 Gy irradiation were reduced by 7.67%.The time of use Tomotherapy radiation system for adaptive plan just need 185.4 minutes.Conclusions: The application of adaptive techniques can reduce the irradiation of OARs.