颈胸段脊椎骨转移癌三维适形与调强放疗剂量学比较的研究

Comparison of Dosimetric Parameters between Three-dimensional Conformal and Intensity-modulated Radiotherapy for Cervicothoracic Spine Metastases

目的:比较颈胸段脊椎骨转移癌的三维适形(3DCRT)和调强放疗(IMRT)的剂量学参数,研究靶区形状对临床方案选择的影响。方法:选择颈胸段脊椎骨转移癌患者10例,分为两类:椎体3例(A组)和椎体+附件7例(B组)。在靶区剂量60Gy,脊髓Dmax≤50Gy且D1(1%体积的剂量)≤45Gy的限制条件下,每病例以4野箱式加上颈段两侧补野设计3DCRT计划一个,5、7、9野共面等机架角静态(Step and shoot)IMRT计划3个。比较和评估DVH、适形指数(CI)、均匀指数(HI)及危及器官剂量学参数等。结果:(1)A组靶区,3DCRT的CI比IMRT小,但是靶区HI优于IMRT;IMRT以5野为佳。(2)B组靶区,IMRT PTV的D80、Dmean均高于3DCRT。5、7、9野IMRT脊髓Dmax分别为<50Gy、49Gy-51Gy、和>50Gy,PTV的CI均值5、7、9野IMRT分别为0.69、0.66、0.69,3DCRT为0.53,IMRT的CI好于3DCRT(P<0.05);5、7、9野IMRT的子野均值分别为83、104、160,总Mu数均值分别为727、755、953。结论:与3DCRT相比,IMRT计划的靶区剂量和CI更好,对OAR的保护也更优。综合来看,5野IMRT为最优选择。

Objective： To compare the dosimetric parameters between three-dimensional conformal and intensity-modulated ra- diotherapy for cervicothoracic spine metastases. Methods： Totally 10 cases of patients with cervicothoracic spine metastases were devided into 2 groups： 3 patients with vertebral metastases; the other 7 patients with vertebral＋annex metastases. The pre- scription dose for gross target was 60 Gy, D~ of spinal cord ~〈50 Gy, D~ ~〈45 Gy. Each patient was designed. One set of 3DCRT plan and three sets of IIVlRT plan were designed for each patient. We used 6 beams for 3DCRT plan, including 2 beams for the upper neck. 3 sets of Step and shoot IMRT plans were consisted of 5-fields, 7-fields and 9-fields, respectively, with e- qual angle and coplanar. DVH. CI and HI dose distributions of PTV and OARs were compared between 3DCRT and different set oflMRT plans. Results： （1）When the gross target included only vertebral, the CI of 3DCRT plan was lower than that oflM- RT plan, but the HI of 3DCRT plan was higher than that of IMRT plan. Moreover, 5-fields IMRT plan was better than other plans. （2） When the gross target included vertebral and annex, the D80,Dmax of IMRT PTV were higher than that of 3DCRT. As for spinal cord, 5-fields Dmax〈50 Gy, 7-fields Dmax=49 Gy-51 Gy, 9-fields Dmax〉50 Gy. The CI of 3 sets of IMRT plans were 0.69, 0.66, 0.69, respectively. The CI of 3DCRT PTV was 0.53, worse than that of IMRT（P〈0.05）. The average segments of 3 sets of IMRT plans were 83, 104, 160, and the average Mu of IMRT plans were 727, 755, 953, respectively. Conclusion： Compared with 3DCRT plan, the dose distribution, OAR and CI of IMRT plans were better. 5-fields IMRT plan is recommended strongly.