Abstract The rotating scatter mask system is capable of determining the direction of a single point gamma or neutron source. However, the point source approximation does not hold for many realistic applications, requiring more detailed reconstructions with this system. This study is the first to characterize the rotating scatter mask as a gamma imager, or camera, through a detailed analysis of the relative error, precision, noise, and convergence time as a measure of reconstruction performance. Simulated 137Cs sources and detector responses were generated in MCNP v6.1.4 and v6.2 with high fidelity and low statistical uncertainty. An analysis of variance was applied to maximum-likelihood expectation–maximization algorithms to determine the most significant factors in reconstructing the image, focusing on the source’s shape, size, and direction relative to the detector. Parameters for a Median Root Prior smoothing function were optimized to balance performance over a variety of source distributions. The algorithm performed reasonably well for point sources and for sources that spanned less than 30 ° in size and were located near the equatorial region of the rotating system. In most other scenarios, the algorithm either oversmoothed the image, resulting in blurry images, or completely failed to reconstruct the image. Increasing the resolution improved the reconstruction quality, while increasing the neighborhood size for the Median Root Prior reduced the image’s noise, but at a significant cost to computational efficiency. These results demonstrate that rotating scatter mask imaging is possible and introduces a potential alternative to other imagers. However, they also demonstrate that new techniques must be developed to increase the system’s performance and robustness for gamma imaging applications.

中文翻译：

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旋转散射掩模成像的最大似然重建

摘要 旋转散射掩模系统能够确定单点伽马或中子源的方向。然而，点源近似并不适用于许多实际应用，需要使用该系统进行更详细的重建。这项研究首次通过详细分析相对误差、精度、噪声和收敛时间作为重建性能的衡量标准，将旋转散射掩模表征为伽马成像器或相机。模拟 137Cs 源和探测器响应是在 MCNP v6.1.4 和 v6.2 中生成的，具有高保真度和低统计不确定性。方差分析应用于最大似然期望最大化算法，以确定重建图像的最重要因素，重点是源的形状、大小、和相对于探测器的方向。中值根先验平滑函数的参数经过优化以平衡各种源分布的性能。对于点源和尺寸小于 30° 且位于旋转系统赤道区域附近的源，该算法执行得相当好。在大多数其他情况下，该算法要么过度平滑图像，导致图像模糊，要么完全无法重建图像。增加分辨率提高了重建质量，同时增加了中值根先验的邻域大小减少了图像的噪声，但会显着降低计算效率。这些结果表明旋转散射掩模成像是可能的，并引入了其他成像器的潜在替代方案。然而，