Department of Medical Radiation Physics, Lund University, Lund, Sweden. Author to whom any correspondence should be addressed.
Phys Med Biol. 2018 Dec 12;63(24):245012. doi: 10.1088/1361-6560/aaf0f1.
This paper presents the development and validation of a Monte Carlo-based singe photon emission computed tomography reconstruction program for parallel-hole collimation contained within the SIMIND Monte Carlo framework. The Monte Carlo code is used as an accurate forward-projector and is combined with a simplified back-projector to perform iterative tomographic reconstruction using the Maximum Likelihood Expectation Maximization and Ordered Subsets Expectation Maximization algorithms, together forming a program called SIMREC. The Monte Carlo simulation transforms the estimated source distribution directly from activity to counts in its projections. Hence, the reconstructed image is expressed in activity without reference to an external calibration. The program is tested using phantom measurements of spheres filled with Tc, Lu and I placed in air and centrally and peripherally in a water-filled elliptical phantom. The feasibility of applying the reconstruction to patients is also demonstrated for a range of radiopharmaceuticals. The deviation in total activity in the spheres ranged between -4.1% and 6.2% compared with the activity determined when preparing the phantom. The SIMREC program was found to be accurate with respect to activity estimation and to reconstruct visually acceptable images within a few hours when applied to patient examples.
本文提出了一种基于蒙特卡罗的单光子发射计算机断层扫描重建程序，用于 SIMIND 蒙特卡罗框架内的平行孔准直。蒙特卡罗代码用作精确的正向投影器，并与简化的反向投影器结合使用，使用最大似然期望最大化和有序子集期望最大化算法进行迭代层析重建，共同形成一个称为 SIMREC 的程序。蒙特卡罗模拟将估计的源分布直接从活动转换为其投影中的计数。因此，重建图像以活动表示，而无需参考外部校准。该程序使用充满 Tc、Lu 和 I 的球体的球形测量值进行测试，这些球体位于空气中和充满水的椭圆形体的中心和外围。还展示了将重建应用于患者的可行性，适用于一系列放射性药物。与制备体模时确定的活性相比，球体中的总活性偏差在-4.1%至 6.2%之间。当应用于患者示例时，SIMREC 程序在几小时内即可准确估计活性并重建视觉上可接受的图像。
