Photon counting detection is a promising approach toward dose reduction in X-ray computed tomography (CT). Full CT reconstruction from a fraction of the detected photons required by energy-integrating detectors has been demonstrated. In medical and industrial CT applications, projection truncation to the region-of-interest (ROI) is another effective way of dose reduction, as information from the ROI is usually sufficient for diagnostic purposes. Truncated projections pose an ill-conditioned inverse problem, which can be improved by including measurements from the exterior region. However, this tradeoff between the interior reconstruction quality and the additional exterior measurement (extra dose) has not been studied. In this paper, we explore the number of detected X-ray photons as a new dimension for measurement engineering. Specifically, we design a flexible, photon-efficient measurement strategy for ROI reconstruction by incorporating the photon statistics at extremely low flux level (16 photons per pixel). The optimized photon-allocation strategy shows a 10- to 15-fold lower normalized mean square error (NMSE) in ROI than truncated projections, and a 2-fold lower NMSE in ROI than whole-volume CT scan. Our analysis in few-photon interior tomography could serve as a new framework for dose-efficient, task-specific X-ray image acquisition design.

中文翻译：

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感兴趣区域断层成像中的光子分配策略

光子计数检测是减少 X 射线计算机断层扫描 (CT) 剂量的一种很有前景的方法。已经证明了从能量积分探测器所需的一小部分探测到的光子进行完整的 CT 重建。在医疗和工业 CT 应用中，将投影截断到感兴趣区域 (ROI) 是另一种降低剂量的有效方法，因为来自 ROI 的信息通常足以用于诊断目的。截断投影会导致病态逆问题，可以通过包括外部区域的测量来改善该问题。然而，尚未研究内部重建质量和额外的外部测量（额外剂量）之间的这种权衡。在本文中，我们探索检测到的 X 射线光子数量作为测量工程的一个新维度。具体来说，我们通过在极低通量水平（每像素 16 个光子）下结合光子统计数据，为 ROI 重建设计了一种灵活、光子高效的测量策略。优化的光子分配策略显示 ROI 中归一化均方误差 (NMSE) 比截断投影低 10 到 15 倍，并且 ROI 中的 NMSE 比全体积 CT 扫描低 2 倍。我们在少光子内部断层扫描中的分析可以作为剂量效率、任务特定的 X 射线图像采集设计的新框架。ROI 中的 NMSE 比全体积 CT 扫描低 2 倍。我们在少光子内部断层扫描中的分析可以作为剂量效率、任务特定的 X 射线图像采集设计的新框架。ROI 中的 NMSE 比全体积 CT 扫描低 2 倍。我们在少光子内部断层扫描中的分析可以作为剂量效率、任务特定的 X 射线图像采集设计的新框架。