目的:构建可同时预测多个器官三维剂量分布的统一模型,自动学习多器官间几何解剖结构对其沉积剂量的影响.方法:收集同一肿瘤类型临床放疗计划,以多个危及器官的各体素为研究对象,其沉积剂量为剂量学特征,采用可学习不同任务间关系的正则化多任务学习方法,建立器官间的任务关系矩阵,构建器官间几何结构与剂量分布的关联.实验以15例鼻咽癌病例的IMRT计划所涉及的危及器官脊髓、脑干和左右腮腺为研究对象建立单模多器官关联,计算其体素预测剂量与临床计划剂量的相对百分误差,研究方法的可行性.结果:10例鼻咽癌IMRT计划用于训练,5例用于测试.测试结果:显示单模多器官方法预测精度较高、数据量需求少,其中脊髓、脑干、左右腮腺的平均体素相对处方剂量百分误差分别为(2.01±0.02)％、(2.65±0.02)％、(2.45±0.02)％和(2.55±0.02)％.结论:提出一种可在同一模型中预测多个器官剂量的单模多器官模型,该模型在提高预测精度的同时避免多次的单器官建模,为实现智能计划设计奠定良好基础.%Objective To establish a three-dimensional (3D) dose prediction model,which can predict multiple organs simultaneously in a single model and automatically learn the effect of the geometric anatomical structure on dose distribution.Methods Clinical radiotherapy plans of patients diagnosed with the same type of tumors were collected and retrospectively analyzed.For every plan,each organs at risk (OAR) voxel was regarded as the study sample and its deposited dose was considered as the dosimetric feature.A regularized multi-task learning method than could learn the relationship among different tasks was employed to establish the relationship matrix among tasks and the correlation between geometric structure and dose distribution among organs.In this experiment,the spinal cord,brainstem and bilateral parotids involved in the intensity-modulated radiotherapy (IMRT) plan of 15 nasopharyngeal cancer patients were utilized to establish the multi-organ prediction model.The relative percentage error between the predicted dose of voxel and the clinical planning dose was calculated to assess the feasibility of the model.Results Ten cases receiving IMRT plans were utilized as the training data,and the remaining five cases were used as the test data.The test results demonstrated a higher prediction accuracy and less data demand.And the average voxel dose errors among the spinal cord,brainstem and the left and right parotids were (2.01±0.02)％,(2.65± 0.02) ％,(2.45± 0.02) ％ and (2.55± 0.02) ％,respectively.Conclusion The proposed model can accurately predict the dose of multiple organs in a single model and avoid the establishment of multiple single-organ prediction models,laying a solid foundation for patient-specific plan quality control and knowledge-based treatment planning.
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