目的 采用混合形变图像配准方法 实现胸腹部和盆腔肿瘤自适应放疗中靶区和危及器官的剂量累加,并与三维适形和调强放疗计划的剂量分布进行剂量学比较.方法选取10例肺癌和6例宫颈癌接受放射治疗的患者,在分次治疗20次后,重新采集CT图像,与计划CT图像进行形变配准,得到修改后的累加剂量,并与3D-CRT和IMRT计划进行靶区及双肺、脊髓、膀胱、直肠等器官的剂量体积直方图比较.结果 累加剂量后的CI和HI值明显优于3D-CRT和IMRT(P<0.05).累加剂量的靶区D95、D98及双肺V20、V30、Dmean,心脏V30、V40,脊髓Dmax,膀胱V30、V40、V50、Dmean,直肠的V40、V45、V50、Dmean均<3D-CRT和IMRT计划(P<0.05).小肠V40、Dmean和股骨头V40、Dmean有所降低,但差异无统计学意义.结论 放疗20次后重新修改放疗计划对胸腹部肿瘤和盆腔肿瘤在提高靶区受照剂量的同时能减少危及器官的实际照射量,降低放疗副作用的发生.%Objective To compare and evaluate the dosimetric difference of adaptive radiation therapy (ART) over conventional intensity modulated radiation therapy (IMRT) and 3D conformable radiation therapy (3D-CRT) when using hybrid deformable image registration (DIR) for dose accumulation in thoracic and pelvic cancer patients. Methods CT images of 10 lung cancer patients and 6 cervical cancer patients who received radiation therapy were obtained for twenty treatment fractions. Then, the ART plan was generated by applying the hybrid DIR to register the fractional and planning CT images to calculate the accumulative dose distribution. Dosimetric parameters of the tumor and the organs at risk (OARs) such as lungs, spinal cord, bladder and rectum were compared with the ART and the conventional 3D-CRT and IMRT plan. Results The CI and HI values in ART plan were statistically significantly (P<0.05) better than the 3D-CRT and IMRT plans. The D95, D98, the lung V20, V30, Dmean, the heart V30, V40, the spinal cord Dmax, the bladder V30, V40, V50, Dmean and the rectum V40, V45, V50, Dmean were all smaller than those in 3D-CRT and IMRT plans (P<0.05). While the intestine V40, Dmean and the caput femoris V40, Dmean decreased in ART plan, but the difference was not statistically significant. Conclusion Replanning after 20 times can achieve better target coverage and OARs sparing, it can potentially reduce the radiation side effect and increase the local control rate in thoracic and pelvic cancer patients.
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