Rentmeester M C M, van der Have F, Beekman F J
Department of Nuclear Medicine, Image Sciences Institute and Department of Pharmacology and Anatomy, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands.
Phys Med Biol. 2007 May 7;52(9):2567-81. doi: 10.1088/0031-9155/52/9/016. Epub 2007 Apr 17.
State-of-the-art multi-pinhole SPECT devices allow for sub-mm resolution imaging of radio-molecule distributions in small laboratory animals. The optimization of multi-pinhole and detector geometries using simulations based on ray-tracing or Monte Carlo algorithms is time-consuming, particularly because many system parameters need to be varied. As an efficient alternative we develop a continuous analytical model of a pinhole SPECT system with a stationary detector set-up, which we apply to focused imaging of a mouse. The model assumes that the multi-pinhole collimator and the detector both have the shape of a spherical layer, and uses analytical expressions for effective pinhole diameters, sensitivity and spatial resolution. For fixed fields-of-view, a pinhole-diameter adapting feedback loop allows for the comparison of the system resolution of different systems at equal system sensitivity, and vice versa. The model predicts that (i) for optimal resolution or sensitivity the collimator layer with pinholes should be placed as closely as possible around the animal given a fixed detector layer, (ii) with high-resolution detectors a resolution improvement up to 31% can be achieved compared to optimized systems, (iii) high-resolution detectors can be placed close to the collimator without significant resolution losses, (iv) interestingly, systems with a physical pinhole diameter of 0 mm can have an excellent resolution when high-resolution detectors are used.
最先进的多针孔单光子发射计算机断层扫描（SPECT）设备能够对小型实验动物体内放射性分子分布进行亚毫米级分辨率成像。使用基于光线追踪或蒙特卡罗算法的模拟来优化多针孔和探测器几何结构非常耗时，尤其是因为许多系统参数需要变化。作为一种有效的替代方法，我们开发了一种具有固定探测器设置的针孔SPECT系统的连续分析模型，并将其应用于小鼠的聚焦成像。该模型假设多针孔准直器和探测器均呈球形层状，并使用有效针孔直径、灵敏度和空间分辨率的解析表达式。对于固定的视野，针孔直径自适应反馈回路允许在相同系统灵敏度下比较不同系统的分辨率，反之亦然。该模型预测：（i）对于最佳分辨率或灵敏度，在给定固定探测器层的情况下，带针孔的准直器层应尽可能靠近动物放置；（ii）与优化系统相比，使用高分辨率探测器可实现高达31%的分辨率提升；（iii）高分辨率探测器可放置在靠近准直器的位置而不会有明显的分辨率损失；（iv）有趣的是，当使用高分辨率探测器时，物理针孔直径为0毫米的系统可具有出色的分辨率。
