Significance: Deep-tissue penetration by x-rays to induce optical responses of specific molecular reporters is a new way to sense and image features of tissue function in vivo. Advances in this field are emerging, as biocompatible probes are invented along with innovations in how to optimally utilize x-ray sources. Aim: A comprehensive review is provided of the many tools and techniques developed for x-ray-induced optical molecular sensing, covering topics ranging from foundations of x-ray fluorescence imaging and x-ray tomography to the adaptation of these methods for sensing and imaging in vivo. Approach: The ways in which x-rays can interact with molecules and lead to their optical luminescence are reviewed, including temporal methods based on gated acquisition and multipoint scanning for improved lateral or axial resolution. Results: While some known probes can generate light upon x-ray scintillation, there has been an emergent recognition that excitation of molecular probes by x-ray-induced Cherenkov light is also possible. Emission of Cherenkov radiation requires a threshold energy of x-rays in the high kV or MV range, but has the advantage of being able to excite a broad range of optical molecular probes. In comparison, most scintillating agents are more readily activated by lower keV x-ray energies but are composed of crystalline inorganic constituents, although some organic biocompatible agents have been designed as well. Methods to create high-resolution structured x-ray-optical images are now available, based upon unique scanning approaches and/or a priori knowledge of the scanned x-ray beam geometry. Further improvements in spatial resolution can be achieved by careful system design and algorithm optimization. Current applications of these hybrid x-ray-optical approaches include imaging of tissue oxygenation and pH as well as of certain fluorescent proteins. Conclusions: Discovery of x-ray-excited reporters combined with optimized x-ray scan sequences can improve imaging resolution and sensitivity.

中文翻译：

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X 射线激发体内光学分子成像和传感综述

意义：通过 X 射线穿透深层组织来诱导特定分子报道分子的光学响应，是一种感知和成像体内组织功能特征的新方法。随着生物相容性探针的发明以及如何最佳利用 X 射线源的创新，该领域正在取得进展。目的：对为 X 射线诱导光学分子传感开发的许多工具和技术进行全面回顾，涵盖从 X 射线荧光成像和 X 射线断层扫描的基础到这些传感和成像方法的适应等主题体内。方法：回顾了 X 射线与分子相互作用并导致其光学发光的方式，包括基于门控采集和多点扫描的时间方法，以提高横向或轴向分辨率。结果：虽然一些已知的探针可以在 X 射线闪烁时产生光，但人们逐渐认识到通过 X 射线诱导的切伦科夫光激发分子探针也是可能的。切伦科夫辐射的发射需要高 kV 或 MV 范围内的 X 射线阈值能量，但具有能够激发多种光学分子探针的优点。相比之下，大多数闪烁剂更容易被较低keV X射线能量激活，但由结晶无机成分组成，尽管也设计了一些有机生物相容剂。基于独特的扫描方法和/或扫描的 X 射线束几何形状的先验知识，现在可以使用创建高分辨率结构化 X 射线光学图像的方法。通过仔细的系统设计和算法优化可以实现空间分辨率的进一步提高。这些混合 X 射线光学方法的当前应用包括组织氧合和 pH 以及某些荧光蛋白的成像。结论：X 射线激发报告基因的发现与优化的 X 射线扫描序列相结合可以提高成像分辨率和灵敏度。