4D-CT重建及其应用研究新进展

New Advance on 4D-CT Reconstruction and It's Application

概述了不同4D—CT重建方法的优缺点及其改进方法，4D—CT在放疗中主要用于研究靶区和正常组织的运动规律、探讨胸腹肿瘤靶区与腹压的关系、分析靶区与内外标记的相关性、勾画肿瘤靶区、设计精确的4D放疗计划、比较剂量分布和进行图像引导放疗。4D放疗计划设计大多采用单相位CT、平均密度投影CT、最大密度投影CT进行，4D—CT数据量约1000张～1500张，使靶区勾画成为4D放疗的首要难题，基于呼吸运动的B一样条拟合模型和迭代模型重建的连续4D—CT可实现靶区自动勾画和计划设计自动化，在4D放疗计划制定的各个环节都需要进行变形图像的配准，4D-4D图像配准能提高4D图像引导放疗的精度。

Various 4D-CT systems with different advantages or disadvantages and the improving methods have been surmmarized in this article. 4D-CT data are mainly used to characterize the anatomy movement of patients, outline the contoures of gross tumor volumes （GTVs） or normal structures, analyze the relationship between target motion and abdominal compression level, study the correlation between tumor motion and internal ftducial or external marker motion, create 4D radiotherapy planning, compare the dose distributions between 3D and 4D treatment plans and deliver image guided radiation thcrapy（IGRT）.4D radiation therapy plans are usually based on single phase or average density projection or maximum density projection CT data. A complete 4D-CT dataset usually contains 1000-1500 slices which result in a great difficult when manually delineate the contours of the anatomy structures on so many slices. The continuous 4D motion model based on approximating B-spline fitting of multiple respiratory cycles and iterative 4D model based on internal anatomy motion are efficacious approaches in automatically outlining the anatomy structures on 4D-CT slices. The registration of deformation images have great importance during 4D radiotherapy planning. 4D--4D image registrations may improve the accuracy of image guided radiation therapy.