Zhang Geoffrey G, Huang Tzung-Chi, Forster Ken M, Lin Kang-Ping, Stevens Craig, Harris Eleanor, Guerrero Thomas
H. Lee Moffitt Cancer Center & Research Institute at the University of South Florida, Radiation Oncology, Tampa, FL 33612, United States.
Comput Methods Programs Biomed. 2008 Apr;90(1):25-37. doi: 10.1016/j.cmpb.2007.11.015. Epub 2008 Feb 21.
The purpose of this paper is to validate a dose mapping program using optical flow method (OFM), and to demonstrate application of the program in radiotherapy follow-up evaluation. For the purpose of validation, the deformation matrices between four-dimensional (4D) CT data of different simulated respiration phases of a phantom were calculated using OFM. The matrices were then used to map doses of all phases to a single-phase image, and summed in equal time weighting. The calculated dose should closely represent the dose delivered to the moving phantom if the deformation matrices are accurately calculated. The measured point doses agreed with the OFM calculations better than 2% at isocenters, and dose distributions better than 1mm for the 50% isodose line. To demonstrate proof-of-concept for the use of deformable image registration in dose mapping for treatment evaluation, the treatment-planning CT was registered with the post-treatment CT image from the positron emission tomography (PET)/CT resulting in a deformation matrix. The dose distribution from the treatment plan was then mapped onto the restaging PET/CT using the deformation matrix. Two cases in which patients had thoracic malignancies are presented. Each patient had CT-based treatment planning for radiotherapy and restaging fluorodeoxy glucose (FDG)-PET/CT imaging 4-6 weeks after completion of treatments. Areas of pneumonitis and recurrence were identified radiographically on both PET and CT restaging images. Local dose and standard uptake values for pneumonitis and recurrence were studied as a demonstration of this method. By comparing the deformable mapped dose to measurement, the treatment evaluation method which is introduced in this manuscript proved to be accurate. It thus provides a more accurate analysis than other rigid or linear dose-image registration when used in studying treatment outcome versus dose.
本文的目的是验证一种使用光流法（OFM）的剂量映射程序，并展示该程序在放射治疗随访评估中的应用。为了进行验证，使用OFM计算了模体不同模拟呼吸阶段的四维（4D）CT数据之间的变形矩阵。然后使用这些矩阵将所有阶段的剂量映射到单相图像上，并以相等的时间权重进行求和。如果变形矩阵计算准确，计算出的剂量应能紧密代表传递到移动模体的剂量。在等中心处，测量的点剂量与OFM计算结果的一致性优于2%，对于50%等剂量线，剂量分布的一致性优于1mm。为了证明在治疗评估的剂量映射中使用可变形图像配准的概念验证，将治疗计划CT与正电子发射断层扫描（PET）/CT的治疗后CT图像进行配准，得到一个变形矩阵。然后使用该变形矩阵将治疗计划的剂量分布映射到再分期PET/CT上。本文展示了两例患有胸段恶性肿瘤的患者。每位患者都进行了基于CT的放射治疗计划，并在治疗完成后4 - 6周进行了再分期氟脱氧葡萄糖（FDG）-PET/CT成像。在PET和CT再分期图像上通过影像学方法识别了肺炎和复发区域。作为该方法的一个示例，研究了肺炎和复发区域的局部剂量和标准摄取值。通过将可变形映射剂量与测量值进行比较，本文介绍的治疗评估方法被证明是准确的。因此，在研究治疗结果与剂量的关系时，与其他刚性或线性剂量 - 图像配准方法相比，它能提供更准确的分析。
