胃癌术后IMRT与常规对穿及适形照射剂量学的比较

Comparing of IMRT、APPA and Conformal Radiotherapy after Resection of Gastric Cancer:a Dosimetric Comparative Analysis

目的比较胃癌术后常规放射治疗与适形及调强(IMRT)治疗技术在同一处方剂量(45 Gy)时的剂量分布特点,为临床提供参考。方法选取9例胃癌术后患者,在CT图像序列上勾画出临床靶区(CTV),CTV外放1 cm定义为计划靶区PTV,对PTV分别用常规两野对穿、适形5野及5野调强照射技术进行计划设计。所有方案处方剂量均为45 Gy,要求95%体积PTV接受45 Gy剂量,IMRT与适形计划采用优化以保证≥95%的PTV接受45 Gy的处方剂量,99%的PTV接受42.75 Gy。根据剂量体积直方图(DVH)比较PTV受量和正常器官的受量差异和剂量分布,并计算正常组织并发症概率(NTCP)。结果IMRT能够产生优于常规及适形的靶区剂量分布,均匀性及适形度明显优于常规对穿照射。IMRT的左肾受23 Gy剂量的体积百分比(V23)明显低于常规及适形技术,从脊髓剂量来看,IMRT的脊髓最大剂量为(39.3+2.3),小于40 Gy,明显优于常规前后对穿及适形照射技术,并相应减少脊髓的NTCP值。结论IMRT相对于常规对穿照射及适形照射具有明显的靶区剂量分布优势,可以减少肾脏、脊髓等正常组织器官的照射体积百分比及NTCP值。

Objective Dose distribution of IMRT,conventional radiotherapy by APPA technique and conform radiotherapy was compared after surgical treatment of gastric cancer. Methods 9 patients with euratively D2 resected gastric cancer were enrolled for this research. Clinical tumor volume （CTV） was contoured on each computed tomography scans. Planning target volume included CTV plus lore margins. Treatment planning of IMRT, conventional radiotherapy and eonformal radiotherapy was done for each patient. The prescribed doses of PTV were 45 Gy,with 95% of PTV receiving the prescribed dose. All IMRT and eonformal plans were optimized to insure ≥95% PTV received 45 Gy,99% PTV receive 42.75 Gy. Dose distribution of PTVs and OARs was compared by using the DVH,and the NTCP was calculated. Results IMRT achieved better dose distribution than conventional and conformal radiotherapy. Dose uniformity and conformal index was significantly better in IMRT than that in conventional radiotherapy. The percentage of volume receiving 23 Gy by left kidney was significantly less in IMRT than in conventional radiotherapy. Maximum close to the spinal cord was（39.3 ＋ 2.3 ）in IMRT,which was significantly less than that in conformal and conventional radiotherapy. Conclusion IMRT could achieve significantly better dose distribution in patients with resected gastric carcinoma.