直肠癌放疗不同技术和体位对小肠受照体积的比较

Influence of modern radiotherapy technique or treatment position on the irradiated volumein small bowel sparing for rectal cancer patients

[目的]探讨仰卧位与俯卧位等体位下实施三维适形(3D-CRT)与调强放射治疗(IMRT)计划对直肠癌患者小肠受照体积的影响。[方法]选择50例直肠癌患者,让其膀胱处于充盈条件下,在仰卧位与俯卧位分别进行CT定位扫描,将扫描图像传输到计划系统。在每一种体位上所得到的CT图像上分别实施3D-CRT与IMRT计划,观察患者在不同技术及体位下小肠受照体积(V5-45)的差异。[结果]在相同的体位(仰卧位或俯卧位)下,与3D-CRT比较,IMRT治疗下小肠V_(45)显著下降(P<0.05),小肠V_(15)则两者较为接近。在相同的放疗技术(3D-CRT或IMRT)下,与仰卧位比较,俯卧位治疗小肠V_(45)与V_(15)均显著下降(P<0.05)。[结论]直肠癌患者在接受体外照射治疗时,治疗体位较放疗技术对患者小肠受照体积的影响更显著。

[Objective]To compare the effect of small bowel sparing between modern radiotherapy technique on intensity modulated radiotherapy（IMRT）and prone position with belly-board for rectal cancer radiotherapy.[Methods]50rectal cancer patients underwent two series of CT scans,prone positioned with a belly board and supine positioned with a flat board,both combined using a full bladder protocol.Supine three dimensional conformal radiotherapy（3D-CRT）,supine IMRT and prone 3D-CRT,prone IMRT plans were constructed for each patient.The volume of small bowel receiving doses in 5Gy increments from（5-45）Gy was calculated using dose-volume histograms for each plan.[Results]Volumes of small bowel receiving dose in 5Gy increments from（5-45）Gy were calculated,from（35-45）Gy,there was a significantly lower volume of small bowel treated using the IMRT technique in both supine and prone positions.Compared with supine position,a trend was found for lower volume of irradiated small bowel at each dose level between 5and 45 Gy for prone position,whether using IMRT or not.The differences in small bowel V_（15）（the absolute volume of small bowel receiving at least 15Gy）and V_（45）（the absolute volume of small bowel receiving at least 45Gy）between supine and prone position were significant.The V_（45） for the small bowel was significantly smaller for IMRT than 3D-CRT,but the V_（15） was approximately equal for IMRT and 3D-CRT.[Conclusion]Patient position had a greater impact on small bowel sparing than modern radiotherapy technique.