Wang Guobao, Qi Jinyi
Department of Biomedical Engineering, University of California, Davis, CA 95616, USA.
IEEE Trans Med Imaging. 2009 Apr;28(4):608-20. doi: 10.1109/TMI.2008.2008971. Epub 2009 Feb 10.
Quantification of tracer kinetics using dynamic positron emission tomography (PET) provides important information for understanding the physiological and biochemical processes in humans and animals. A common procedure is to reconstruct a sequence of dynamic images first, and then apply kinetic analysis to the time activity curve of a region of interest derived from the reconstructed images. Obviously, the choice of image reconstruction method and its parameters affect the accuracy of the time activity curve and hence the estimated kinetic parameters. This paper analyzes the effects of penalized likelihood image reconstruction on tracer kinetic parameter estimation. Approximate theoretical expressions are derived to study the bias, variance, and ensemble mean squared error of the estimated kinetic parameters. Computer simulations show that these formulae predict correctly the changes of these statistics as functions of the regularization parameter. It is found that the choice of the regularization parameter has a significant impact on kinetic parameter estimation, indicating proper selection of image reconstruction parameters is important for dynamic PET. A practical method has been developed to use the theoretical formulae to guide the selection of the regularization parameter in dynamic PET image reconstruction.
使用动态正电子发射断层扫描（PET）对示踪剂动力学进行定量分析可为理解人类和动物的生理及生化过程提供重要信息。一种常见的做法是先重建一系列动态图像，然后对从重建图像中获取的感兴趣区域的时间-活度曲线进行动力学分析。显然，图像重建方法及其参数的选择会影响时间-活度曲线的准确性，进而影响估计的动力学参数。本文分析了惩罚似然图像重建对示踪剂动力学参数估计的影响。推导了近似理论表达式，以研究估计动力学参数的偏差、方差和总体均方误差。计算机模拟表明，这些公式能正确预测这些统计量随正则化参数的变化。研究发现，正则化参数的选择对动力学参数估计有显著影响，这表明在动态PET中正确选择图像重建参数很重要。已开发出一种实用方法，利用理论公式指导动态PET图像重建中正则化参数的选择。
