Floyd C E, Jaszczak R J, Greer K L, Coleman R E
J Nucl Med. 1986 Oct;27(10):1577-85.
Tomographic reconstruction for single photon emission computed tomography (SPECT) with simultaneous compensation for attenuation, scatter, and distance dependent collimator resolution is provided by an Inverse Monte Carlo (IMOC) reconstruction algorithm. A detection probability matrix is formed by Monte Carlo solution to the photon transport equation for SPECT acquisition from a unit source activity in each reconstruction source voxel. The measured projection vector will equal the product of this detection probability matrix with the unknown source distribution vector. The resulting large, nonsparse system of equations is solved for the source distribution using an iterative Maximum Likelihood EM estimator. Reconstruction of experimentally acquired projections from phantoms shows quantitative compensation for scatter and attenuation. Comparison with filtered backprojection (FBP) reconstruction shows an improvement in resolution recovery, contrast, and signal-to-noise for the IMOC algorithm. Reconstruction of clinical studies shows improved contrast, structural resolution, and noise characteristics.
逆蒙特卡罗（IMOC）重建算法可实现单光子发射计算机断层扫描（SPECT）的断层重建，同时对衰减、散射和距离相关的准直器分辨率进行补偿。通过蒙特卡罗方法求解光子输运方程，为每个重建源体素中的单位源活度进行SPECT采集，从而形成检测概率矩阵。测量得到的投影向量将等于该检测概率矩阵与未知源分布向量的乘积。使用迭代最大似然期望最大化（EM）估计器求解由此产生的大型非稀疏方程组，以得到源分布。对体模实验采集投影的重建显示了对散射和衰减的定量补偿。与滤波反投影（FBP）重建的比较表明，IMOC算法在分辨率恢复、对比度和信噪比方面有所改善。临床研究的重建显示出对比度、结构分辨率和噪声特性的改善。
