显微CT系统中的通用相位衬度
Universal Phase Contrast in Micro-CT Systems
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中文总结 AI 辅助
本研究指出传统显微CT系统无需可见菲涅耳条纹即可存在相位诱导分辨率增强，推导了硬件与探测器诱导相位检索的分析条件并通过实验验证，改变了对其成像机制的解读。
中文摘要 AI 辅助
传统高分辨率显微CT系统被视为基于衰减成像，除非可见的菲涅耳条纹表明存在基于传播的相位衬度。本文表明该解释并不完整：当传播诱导的相位转移相对于系统模糊不可忽略时，显微CT处于相位转移 regime，此时无论菲涅耳条纹是否可见，传播都会相对于仅由源和探测器模糊预期的情况提升空间分辨率。由于显微CT系统具有有限的源和探测器模糊，该相位转移伴随一定程度的硬件诱导相位检索（HIPR），范围从HIPR不足到匹配HIPR再到HIPR过度。我们进一步将探测器诱导相位检索（DIPR）确定为最优情况，此时探测器提供相位检索所需的全部滤波，从而保留相位诱导的分辨率增强，同时在探测光子间引入空间相关性以降低高频噪声。我们推导了HIPR和DIPR的分析条件，引入量化保留相位转移和探测器兼容性的频域指标，并通过模拟及定制和商用显微CT系统的实验数值验证了该框架。结果表明，传统显微CT系统即使在无可见菲涅耳条纹时也可出现相位诱导的分辨率增强，改变了对成像形成、空间分辨率及优化的解读方式。
英文摘要
Conventional high-resolution micro-CT systems are regarded as attenuation-based unless visible Fresnel fringes reveal the presence of propagation-based phase contrast. Here we show that this interpretation is incomplete. When propagation-induced phase transfer is non-negligible relative to the system blur, micro-CT operates in a phase-transfer regime in which propagation improves spatial resolution relative to that expected from source and detector blur alone, irrespective of whether Fresnel fringes remain visible. Because micro-CT systems possess finite source and detector blur, this phase transfer is accompanied by a degree of hardware-induced phase retrieval (HIPR), ranging from under-HIPR to matched-HIPR and over-HIPR. We further identify detector-induced phase retrieval (DIPR) as the optimal case in which the detector provides all of the filtering required for phase retrieval, thereby preserving the phase-induced resolution enhancement while introducing spatial correlations between detected photons that reduce high-spatial-frequency noise. We derive analytical conditions for HIPR and DIPR, introduce frequency-domain metrics quantifying preserved phase transfer and detector compatibility, and validate the framework numerically with simulations and experimentally using custom and commercial micro-CT systems. Our results demonstrate that phase-induced resolution enhancement can occur in conventional micro-CT systems even in the absence of visible Fresnel fringes, changing how image formation, spatial resolution, and optimization should be interpreted.
