直肠癌三维适形和调强放疗物理计划的比较研究

Comparison of 3-dimension conformal and intensity-modulated radiation therapy plans for rectum cancer

目的:探讨三维适形和调强放疗对直肠癌放疗的物理计划特点。方法:选取5例直肠癌病例,进行CT扫描、靶区勾画和三维图像结构重建,分别在Cadplan治疗计划系统上进行三维适形和空间等分的3、5、7、9野的调强放疗计划设计,并对每一计划作出评价。结果:(1)三维适形放疗计划可满足计划靶体积(PTV)剂量要求,但重要器官的剂量分布较差。(2)4个调强放疗计划的PTV和重要器官剂量学参数均优于三维适形放疗计划,差异有统计学意义(P均<0.05),调强放疗计划间各项参数相互比较差异无统计学意义(P均>0.05)。结论:调强放疗在对直肠癌的放疗中较三维适形放疗有剂量分布的优越性。3野的调强放疗基本可以满足PTV和重要器官的剂量学要求,5野的调强放疗计划最优,7野和9野的调强放疗计划未能显示剂量学的优越性。

Objective： To investigate the characteristics of 3-dimension conformal （3D-CRT） and intensitymodulated radiation therapy （IMRT） plans in rectum cancer. Method： Five cases with rectum cancer were chosen to join this study. Several steps including CT scan, target contouring and reconstruction of 3D digital structures were taken before treatment plans were designed through a Cadplan computerized system which allowed a 3D-CRT and 4 IMRT plans with 3, 5, 7 and 9 equispaced coplanar intensity-modulated beams to be produced. Results： （1） 3D-CRT plans could generally meet the demand of dose-volume constraints for PTV（Planning Target Volume） but less conformity for organs at risk. （2） IMRT plans were significantly superior to 3D-CRT plans and no statistical significance was found among IMRT plans in relate to dosimetric parameters. Conclusions： IMRT plans show a superior dose distribution over 3D-CRT and as less as 3 fields of IMRT basically meets the requirement of high dose coverage and a dose homogeneity for PTV and sparing of organs at risk. Comparatively, 5 fields of IMRT plan may achieve an optimal dose-volume constraints without compromising the quality of the treatment while 7 and 9 fields of IMRT do not display a dosimetric superiority over other IMRT plans.