磁场对鼻咽癌放射治疗剂量学的影响

The Dosimetric Effect of Magnetic Field in Nasopharyngeal Cancer Radiation Therapy

目的:比较1.5T与0T磁场下鼻咽癌治疗计划的剂量学差异。方法:对7例鼻咽癌患者制定0T磁场下的治疗计划,分别计算0T和1.5T磁场下的剂量分布,比较两者的PTV的D2%、D95%、D50%与危及器官的最大剂量与平均剂量。结果:1.5T磁场下,PTVnd的D95%和D50%分别降低了4.4%(P=0.005)和1.1%(P=0.005);PTV2的D95%和D50%分别降低了2.6%(P=0.007)和2.0%(P=0.021),D2%增加了2.4%;皮肤和左侧晶体的最大剂量分别增加11.1%(P=0.016)和4.9%(P=0.028);皮肤,左侧腮腺和右侧腮腺的平均剂量分别增加3.5%(P=0.005),15.1%(P=0.005)和12.8%(P=0.005);其余靶区和危及器官的剂量学参数均无显著性差异(P>0.05)。结论:1.5T磁场对鼻咽癌计划的剂量学参数影响较小,但不可忽略,尤其是皮肤和腮腺,在计划优化过程中应加入磁场因素。

Purpose:To compare the dosimetric difference in the treatment plans of nasopharyngeal cancer under1.5 T and 0 T magnetic field.Methods:Treatment plans of seven patients under 0 T and 1.5 T magnetic field with nasopharyngeal cancer were used in this study.The dose distribution parameters including D2%,D95%,D50%of target volume,Dmax and Dmean of organs at risk were calculated and compared respectively.Results:Compared with the results of 0 T magnetic field,the D95%and D50%of PTVnd under 1.5 T magnetic field decreased by 4.4%(P=0.005)and 1.1%(P=0.005),respectively,and the D95%and D50%of PTV2 decreased by 2.6%(P=0.007)and2.0%(P=0.021),respectively,D2%was increased by 2.4%;the maximum dose of skin and lens increased by 11.1%(P=0.016)and 4.9%(P=0.028),respectively;the Dmean of skin,left and right parotid gland increased by 3.5%(P=0.005),15.1%(P=0.005)and 12.8%(P=0.005),respectively.Other dosimetric parameters of planning target volume and OARs under 0 T and 1.5 T magnetic field were with no significant difference(P>0.05).Conclusions:The dosimetric effect of 1.5 T magnetic field on the nasopharyngeal cancer plans is small but not negligible,especially in the skin and parotid gland.Thus,the magnetic field should be included in the plan optimization process.