Department of Biomedical Engineering, University of California, Davis, CA 95616, USA.
IEEE Trans Med Imaging. 2009 Nov;28(11):1717-26. doi: 10.1109/TMI.2009.2021851. Epub 2009 May 12.
Indirect and direct methods have been developed for reconstructing parametric images from dynamic positron emission tomography (PET) data. Indirect methods are simple and easy to implement because reconstruction and kinetic modeling are performed in two separate steps. Direct methods estimate parametric images directly from dynamic PET sinograms and, in theory, can be statistically more efficient, but the algorithms are often difficult to implement and are very specific to the kinetic model being used. This paper presents a class of generalized algorithms for direct reconstruction of parametric images that are relatively easy to implement and can be adapted to different kinetic models. The proposed algorithms use optimization transfer principle to convert the maximization of a penalized likelihood into a pixel-wise weighted least squares (WLS) kinetic fitting problem at each iteration. Thus, it can employ existing WLS algorithms developed for kinetic models. The proposed algorithms resemble the empirical iterative implementation of the indirect approach, but converge to a solution of the direct formulation. Computer simulations showed that the proposed direct reconstruction algorithms are flexible and achieve a better bias-variance tradeoff than indirect reconstruction methods.
已经开发出了从动态正电子发射断层扫描（PET）数据重建参数图像的间接和直接方法。间接方法简单易用，因为重建和动力学建模是在两个单独的步骤中进行的。直接方法直接从动态 PET 正弦图估计参数图像，从理论上讲，在统计学上可以更有效，但算法通常难以实现，并且非常特定于正在使用的动力学模型。本文提出了一类用于直接重建参数图像的广义算法，这些算法相对容易实现，可以适应不同的动力学模型。所提出的算法使用优化传递原理将惩罚似然函数的最大化转换为每次迭代时的像素加权最小二乘（WLS）动力学拟合问题。因此，它可以采用为动力学模型开发的现有 WLS 算法。所提出的算法类似于间接方法的经验迭代实现，但收敛于直接公式的解。计算机模拟表明，所提出的直接重建算法具有灵活性，并且比间接重建方法实现了更好的偏差方差权衡。
