Model-based image reconstruction for four-dimensional PET
Model-based image reconstruction for four-dimensional PET
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DOI：
10.1118/1.2192581
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发表时间：
2006-05-01
期刊：
影响因子：
3.8
通讯作者：
Xing, Lei
中科院分区：
文献类型：
--
作者：
Li, Tianfang;Thorndyke, Brian;Xing, Lei
正电子放射性成像（PET）可用于多种癌症的诊断和放射治疗计划。对于胸部或上腹部的癌症患者，呼吸运动会使肿瘤的形状和大小产生较大的失真，影响诊断和治疗的准确性。四维（4D）（门控）PET旨在减少运动伪影，并提供肿瘤体积和示踪剂浓度的准确测量。4D PET的一个主要问题是缺乏统计数据。由于收集的光子在4D PET扫描中被分成若干帧，因此每个重建帧的质量随着帧数量的增加而降低。每帧中增加的噪声严重降低PET成像的定量准确性。在这项工作中，我们提出了一种方法来提高4D PET的性能，通过开发一种新的4D PET重建技术，结合来自4D-CT图像的器官运动模型。该方法是基于著名的最大似然期望最大化（ML-EM）算法。在ML-EM迭代的前向投影和后向投影过程中，将不同阶段采集的投影数据结合在一起，借助变形模型更新发射图，从而大大改善了统计特性。所提出的算法首先进行了评估与计算机模拟使用的数学动态幻影。然后进行了实验与移动的物理体模，以证明所提出的方法的准确性和增加的信噪比比三维PET。最后，将4D PET重建应用于患者病例。(c)2006年美国医学物理学家协会。
Positron emission tonography (PET) is useful in diagnosis and radiation treatment planning for a variety of cancers. For patients with cancers in thoracic or upper abdominal region, the respiratory motion produces large distortions in the tumor shape and size, affecting the accuracy in both diagnosis and treatment. Four-dimensional (4D) (gated) PET aims to reduce the motion artifacts and to provide accurate measurement of the tumor volume and the tracer concentration. A major issue in 4D PET is the lack of statistics. Since the collected photons are divided into several frames in the 4D PET scan, the quality of each reconstructed frame degrades as the number of frames increases. The increased noise in each frame heavily degrades the quantitative accuracy of the PET imaging. In this work, we propose a method to enhance the performance of 4D PET by developing a new technique of 4D PET reconstruction with incorporation of an organ motion model derived from 4D-CT images. The method is based on the well-known maximum-likelihood expectation-maximization (ML-EM) algorithm. During the processes of forward- and backward-projection in the ML-EM iterations, all projection data acquired at different phases are combined together to update the emission map with the aid of deformable model, the statistics is therefore greatly improved. The proposed algorithm was first evaluated with computer simulations using a mathematical dynamic phantom. Experiment with a moving physical phantom was then carried out to demonstrate the accuracy of the proposed method and the increase of signal-to-noise ratio over three-dimensional PET. Finally, the 4D PET reconstruction was applied to a patient case. (c) 2006 American Association of Physicists in Medicine.