基于经验计划的VMAT和IMRT模型预测前列腺IMRT剂量分布的对比研究

目的 比较基于知识计划(KBP)的容积调强弧形治疗(VMAT)模型和固定野调强放疗(IMRT)模型预测前列腺IMRT计划的剂量学差异,探讨利用VMAT模型预测IMRT计划的可行性。方法 选取已完成放疗的前列腺癌病例50例,每个病例分别设计VMAT和IMRT计划。随机选取40个病例的VMAT计划和IMRT计划作为训练样本,分别训练得到VMAT模型和IMRT模型。剩余10个病例作为预测病例进行IMRT计划预测,得到VMAT模型下的IMRT计划(V-IMRT)和IMRT模型下的IMRT计划(I-IMRT)。对预测组人工计划(mIMRT)、V-IMRT和I-IMRT的计划靶区、危及器官进行统计学分析。结果 与mIMRT计划相比,I-IMRT对计划靶区的Dmax控制较好(P=0.039),V-IMRT和I-IMRT对膀胱和左右股骨头保护更好(P<0.05)。比较两组自动计划,V-IMRT计划对左股骨头的Dmax和右侧股骨头的D15%保护好于I-IMRT (P<0.05),其他均相近(P>0.05)。结论 和人工计划比,KBP的IMRT计划对危及器官保护有明显优势;用KBP的VMAT模型预测IMRT计划和IMRT模型预测IMRT计划相近,在临床上可行。

A comparative study of dose distribution of prostate IMRT between IMRT and VMAT models using knowledge-based planning

Objective To compare the dosimetric difference between knowledge-based planning (KBP) volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) models for predicting the dose distribution during IMRT, aiming to investigate the feasibility of VMAT model to predict the IMRT plans. Methods Fifty prostate cancer patients who had completed radiotherapy were selected. Manual planning was performed on each selected patient to generate the corresponding IMRT and VMAT plans. The IMRT and VMAT manual plans of the 40 randomly-selected patients were adopted to generate the KBP VMAT and IMRT models. The remaining 10 patients were utilized to predict IMRT plans. VMAT library-derived IMRT model (V-IMRT) and IMRT library-derived IMRT model (I-IMRT) were generated. Dosimetric parameters related to organ-at-risks (OARs) and planning target volume (PTV) were statistically compared among the manual IMRT (mIMRT), V-IMRT and I-IMRT plans. Results Compared with the mIMRT plan, I-IMRT could significantly better control Dmax of the PTV (P=0.039), whereas V-IMRT and I-IMRT plans could better protect the bladder and bilateral femoral heads (both P<0.05). V-IMRT plan could better protect the Dmax of bilateral femoral heads and the D15% of the right femoral head (both P<0.05), whereas no significant difference was observed in other OARs and PTV (all P>0.05). Conclusions Compared with the manual plans, KBP IMRT plan has significant advantages in protecting the OARs. KBP VMAT and IMRT models are both feasible in clinical practice, which yield equivalent accuracy for predicting IMRT plan.