Ardekani B A, Braun M, Hutton B F, Kanno I, Iida H
Department of Radiology and Nuclear Medicine, Research Institute for Brain and Blood Vessels, Akita, Japan.
Phys Med Biol. 1996 Nov;41(11):2497-517. doi: 10.1088/0031-9155/41/11/018.
An algorithm is presented for the reconstruction of PET images using prior anatomical information derived from MR images of the same subject. The cross-entropy or Kullback-Leiber distance is a measure of dissimilarity between two images. We propose to reconstruct PET images by minimizing a weighted sum of two cross-entropy terms. The first is the cross-entropy between the measured emission data and the forward projection of the current estimate of the PET image. Minimizing this term alone is equivalent to the ML-EM reconstruction. The second term is the cross-entropy between the current estimate of the PET image and a prior image model which incorporates anatomical information derived from registered MR images. A weighting parameter determines the relative emphasis given to the emission data and the prior model in the reconstruction. Details of this algorithm are presented as well as test reconstructions for real and simulated data. The performance of the algorithm was evaluated with respect to errors in prior anatomical information. The algorithm provided significant improvement in the quality of reconstructed images as compared with the ML-EM reconstruction technique. The reconstructed images had higher resolution as compared with the images obtained from MAP-like reconstructions which do not utilize anatomical information. The algorithm displayed robustness with respect to errors in prior anatomical information.
本文提出了一种利用同一受试者的磁共振图像获取的先验解剖学信息来重建正电子发射断层扫描（PET）图像的算法。交叉熵或库尔贝克 - 莱布勒散度是衡量两幅图像差异的一种度量。我们建议通过最小化两个交叉熵项的加权和来重建PET图像。第一个是测量的发射数据与PET图像当前估计值的前向投影之间的交叉熵。仅最小化该项等同于最大似然期望最大化（ML-EM）重建。第二项是PET图像当前估计值与一个先验图像模型之间的交叉熵，该先验图像模型包含从配准后的磁共振图像中获取的解剖学信息。一个加权参数决定了在重建过程中对发射数据和先验模型的相对重视程度。本文给出了该算法的详细内容以及对真实数据和模拟数据的测试重建结果。针对先验解剖学信息中的误差对该算法的性能进行了评估。与ML-EM重建技术相比，该算法在重建图像质量方面有显著提升。与未利用解剖学信息的类似最大后验概率（MAP）重建所获得的图像相比，重建图像具有更高的分辨率。该算法在先验解剖学信息存在误差的情况下表现出了鲁棒性。
