3D打印个体化模体在胸部调强治疗计划中的剂量学研究

A dosimetric study of 3D-printed individual phantom in intensity modulated radiation therapy plan for chest

目的:利用3D打印技术制作反映患者真实情况的3D打印个体化模体,分析3D打印个体化模体内各器官CT值及放射治疗剂量分布。方法:根据患者定位CT图像重建并3D打印出各器官的三维立体结构空壳,以CT值为依据选择各器官的等效材料进行填充,即得到体现患者结构特征的个体化胸部模体。将患者治疗计划纳入患者图像组,将患者治疗计划移植到3D打印个体化模体上的计划纳入模体图像组,比较两组计划的剂量学参数。结果:模体图像组患者图像的左右肺脏、软组织、骨松质、骨密质和心脏的平均CT值分别为-709、-737、14、144、760和28 HU。模体图像CT值与患者定位图像CT值比较,误差均<16.7%。两组图像上放射治疗计划的正常组织受量均能满足临床要求;靶区剂量学参数最小剂量(Dmin)、平均剂量(Dmean)、98%、50%和2%的靶区体积对应的剂量(D98%、D50%和D2%)、适形指数(CI)、均匀指数(HI)、机器跳数(MU)均能满足临床要求,且均无统计学差异;靶区最大剂量(Dmax)差异有统计学意义(t=2.678,P<0.05),其中模体图像组Dmax偏大,为(56.97±0.32)Gy。结论:最终设计的模体在放射治疗中的CT值、组织结构、空间分布上均可以仿真人体胸部,验证了3D打印模体在放射治疗质量保证中用于剂量测量的可行性。

Objective:To make an individual phantom that was printed by using three dimension(3D)technique,which could reflect the real situation of patient,and to analyze the computed tomography(CT)value and dose distribution of radiotherapy on each organ of the inside of the 3D-printed individual phantom.Methods:According to the localization of CT image of the patient,the empty shell of 3D structure of each organ were reconstructed and printed by using 3D technique.The CT value was used as basis to select the equivalent material of each organ to perform fill,which could obtain the individual phantom of chest that could appear the structural characteristics of patient.The treatment plan of patients were included in treatment plan group,and the plans which were transplanted to 3D-printed individual phantom from treatment plan of patients were included in phantom plan group.The dosimetric parameters of the plans of two groups were compared.Results:The average CT values of left and right lung,soft tissue,cancellous bone,compact bone and heart of the phantom plan group were respectively-709,-737,14,144,760 and 28 HU.The errors of the all CT values between phantom images and located images of patients were less than 16.7%.The exposure doses of normal tissues of radiotherapy plans on the images of two groups could meet the clinical requirements.The minimum dose(Dmin),mean dose(Dmean),the corresponding doses of 98%,50%and 2%target volumes(D98%,D50%and D2%),conformity index(CI),homogeneity index(HI),monitor unit(MU)of dosimetric parameters of the target region could meet the clinical requirements without statistically significant differences.There was significant differences in the maximum dose(Dmax)of the target region(t=2.678,P<0.05).Among of these Dmax values,the Dmax value of phantom plan group was larger,which was(56.97±0.32)Gy.Conclusion:The CT value,tissue structure and spatial distribution of the phantom,which is finally designed,can emulate the chest of human body in radiotherapy.It has verified the feasibility that 3D-printed phantom is applied in measuring dose in the quality assurance of radiotherapy.