In vivo tomographic imaging of fluorescence protein

描述(申请人提供)：该荧光蛋白已被证明是研究体内细胞和生物体功能的强大探针。使用稳定表达荧光蛋白的肿瘤动物模型使直接观察活动物的细胞行为和生物相互作用成为可能。荧光蛋白成像可以在分子水平上监测肿瘤的生理和病理活动，特别是对原发肿瘤的生长、肿瘤细胞的转移以及肿瘤与其微环境的关系进行可视化。目前的平面荧光蛋白质成像只能在皮肤表面附近提供良好的分辨率，不能分辨深度和量化特征。荧光蛋白层析成像有望提供优越的成像性能来定位和定量体内的荧光蛋白，并显著提高荧光蛋白在动物和人类研究中的应用。然而，荧光蛋白质在可见光光谱中发射光子，生物组织在可见光光谱中对光子的吸收比近红外范围强得多。目前流行的扩散近似模型不适用于描述荧光光子在生物组织中的传播。物理模型失配将严重影响荧光断层扫描重建的质量。此外，荧光蛋白质层析成像是一个典型的欠定问题。重建的独特性和稳定性仍然是重大的技术挑战。为了解决目前荧光断层成像的主要局限性，本项目的总体目标是开发一种新的光子传播模型、相关的重建方法和成像系统来定位和定量活着的小鼠体内的荧光细胞。具体目标是(1)设计一种新型的基于三镜的多视角光子信号同时采集成像系统。该系统结合了透照和表照两种成像模式，具有较强的探测深层探针和浅层目标的能力；(2)发展了一种新的相位近似模型来精确描述组织中的光子在可见光光谱范围内的传播，而不是使用流行的扩散近似模型；(3)建立了描述小鼠解剖和组织光学特性的最佳数值模型；(4)提出了一种差分进化(DE)方法来重建荧光源。该DE算法能够以较快的收敛速度找到真正的全局最优解，使得荧光层析成像更加准确和稳定。(5)在数值模拟、模型实验和小鼠实验中验证了所提出的荧光蛋白质层析成像系统和方法。该项目完成后，该系统将经过验证，荧光源定位的精度为0.7 mm，光能估计误差为15%，与当前系统的性能相比，这意味着&gt；30%的改进。与公众健康相关：在这个项目中，我们提出了一种新的光子传播模型、相关的重建方法和成像系统，以解决目前荧光层析成像的主要局限性，这将显著提高荧光蛋白质层析成像的准确性和稳定性。这将对研究活体动物和患者的各种生理和病理过程，监测原发肿瘤的生长、肿瘤细胞转移、药代动力学和治疗反应具有重要意义。

DESCRIPTION (provided by applicant): The fluorescence protein has proven to be a powerful probe for investigating the functionalities of cells and organisms in vivo. The animal models of tumors that use a stable expression of fluorescent proteins have made it possible to observe directly cellular behaviors and biological interactions in living animals. Fluorescence protein imaging can be used to monitor physiological and pathological activities at molecular levels, specially visualize primary tumor growth, tumor cell metastasis, and the relationship between the tumor and its microenvironment. Current planar fluorescence protein imaging only provides good resolution near the skin surface, and cannot resolve depth and quantify features. Fluorescence protein tomography promises to offer a superior imaging performance to localize and quantify fluorescence proteins in vivo, and significantly enhance the utilities of fluorescent proteins in animal and human studies. However, the fluorescence proteins emit photons in the visible light spectrum, where the biological tissue absorbs photons much more strongly than in the near-infrared range. The popular diffusion approximation model is not suitable to describe the fluorescent photon propagation in biological tissues. The physical model mismatch would significantly compromise the quality of fluorescent tomographic reconstruction. Moreover, fluorescence protein tomography is a typical underdetermined problem. The uniqueness and stability of reconstruction remain major technical challenges. To solve the current major limitations of fluorescence tomographic imaging, the overall goal of this project is to develop a novel photon propagation model, associated reconstruction methods and an imaging system to localize and quantify the fluorescence cells in a living mouse. The specific aims are to (1) design a novel three-mirror-based imaging system for simultaneous acquisition of multi-view photon signals. The system unifies the transillumination and epi-illumination imaging modes, and offers a notable capability of probing both deeply-seated probes and superficial targets in the mouse; (2) develop a novel phase approximation model to describe photon propagation accurately in the tissues over the visible light spectral range instead of using the popular diffusion approximation model; (3) establish an optimal numerical model to describe the mouse anatomy and tissue optical properties; (4) present a differential evolution (DE) approach for the fluorescent source reconstruction. This DE algorithm is able to find the true global optimization solution at a fast convergence rate, making the fluorescence tomographic imaging more accurate and stable, and (5) validate the proposed fluorescence protein tomography system and methods in numerical simulation, phantom experiments and mouse studies. Upon the completion of this project, the system will have been validated with <0.7mm accuracy in fluorescent source localization and <15% error in light energy estimation, which represent >30% improvement as compared to the performance of the current systems. PUBLIC HEALTH RELEVANCE: In this project, we propose a novel photon propagation model, associated reconstruction methods and an imaging system to solve the current major limitations of fluorescence tomographic imaging, which would significantly enhance the accuracy and stability of tomographic imaging of fluorescence proteins. This would be important to study a variety of physiological and pathological processes in living animals and patients, and monitor primary tumor growth, tumor cell metastasis, pharmacokinetics and therapeutic responses.