Efficient fully 3-D iterative SPECT reconstruction with Monte Carlo-based scatter compensation
Efficient fully 3-D iterative SPECT reconstruction with Monte Carlo-based scatter compensation
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DOI：
10.1109/tmi.2002.803130
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发表时间：
2002-08-01
影响因子：
10.6
通讯作者：
van Geloven, S
中科院分区：
文献类型：
--
作者：
Beekman, FJ;de Jong, HWAM;van Geloven, S
单光子发射计算机断层扫描 (SPECT) 图像的定量精度高度依赖于用于图像重建的光子散射模型。蒙特卡罗模拟 (MCS) 是散射详细建模的最通用方法，但迄今为止，由于计算时间过长和计算机内存需求过多，完全基于三维 (3-D) MCS 的统计 SPECT 重建方法尚未实现。基于 MCS 的重建以前仅限于二维方法，远不如完全 3D 重建。有时，全 3D SPECT 重建算法中会采用基于简化但不太准确的模型的散射计算来代替 MCS。我们通过结合以下方法开发了计算高效的全 3D MCS 重建架构：1）双矩阵有序子集（DM-OS）重建算法，以加速重建并避免大量过渡矩阵预计算和存储； 2) MCS 中的随机光子传输计算与分析探测器建模步骤相结合，以减少仅跟踪少量光子历史后基于蒙特卡罗 (MC) 的重投影中的噪声； 3)在早期迭代中模拟的光子历史的数量减少一个数量级，或者重用早期迭代中计算的光子历史。对于 64 x 64 x 64 图像阵列，在双处理器 (AMD 1.4 GHz) PC 上十次 DM-OS 迭代所需的重建时间约为 30 分钟，在这种情况下，MCS 建模的随机性质对重建中的噪声影响可以忽略不计。由于 MCS 可以计算任何临床使用的光子能量和患者衰减分布的光子传输，因此所提出的方法预计将有助于在临床可接受的计算时间内获得高度准确的定量 SPECT 图像。
Quantitative accuracy of single photon emission computed tomography (SPECT) images is highly dependent on the photon scatter model used for image reconstruction. Monte Carlo simulation (MCS) is the most general method for detailed modeling of scatter, but to date, fully three-dimensional (3-D) MCS-based statistical SPECT reconstruction approaches have not been realized, due to prohibitively long computation times and excessive computer memory requirements. MCS-based reconstruction has previously been restricted to two-dimensional approaches that are vastly inferior to fully 3-D reconstruction. Instead of MCS, scatter calculations based on simplified but less accurate models are sometimes incorporated in fully 3-D SPECT reconstruction algorithms.We developed a computationally efficient fully 3-D MCS-based reconstruction architecture by combining the following methods: 1) a dual matrix ordered subset (DM-OS) reconstruction algorithm to accelerate the reconstruction and avoid massive transition matrix precalculation and storage; 2) a stochastic photon transport calculation in MCS is combined with an analytic detector modeling step to reduce noise in the Monte Carlo (MC)-based reprojection after only a small number of photon histories have been tracked; and 3) the number of photon histories simulated is reduced by an order of magnitude in early iterations, or photon histories calculated in an early iteration are reused. For a 64 x 64 x 64 image array, the reconstruction time required for ten DM-OS iterations is approximately 30 min on a dual processor (AMD 1.4 GHz) PC, in which case the stochastic nature of MCS modeling is found to have a negligible effect on noise in reconstructions. Since MCS can calculate photon transport for any clinically used photon energy and patient attenuation distribution, the proposed methodology is expected to be useful for obtaining highly accurate quantitative SPECT images within clinically acceptable computation times.