Graves Edward E, Ripoll Jorge, Weissleder Ralph, Ntziachristos Vasilis
Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Med Phys. 2003 May;30(5):901-11. doi: 10.1118/1.1568977.
Most current imaging systems developed for tomographic investigations of intact tissues using diffuse photons suffer from a limited number of sources and detectors. In this paper we describe the construction and evaluation of a large dataset, low noise tomographic system for fluorescence imaging in small animals. The system consists of a parallel plate-imaging chamber and a lens coupled CCD camera, which enables conventional planar imaging as well as fluorescence tomography. The planar imaging data are used to guide the acquisition of a Fluorescence Molecular Tomography (FMT) dataset containing more than 106 measurements, and to superimpose anatomical features with tomographic results for improved visual representation. Experimental measurements exhibited good agreement with the diffusion theory models used to predict light propagation within the chamber. Tests of the instrument's capacity to quantitatively reconstruct fluorochrome distributions in three dimensions showed less than 5% errors between actual fluorochrome concentrations and FMT findings, and suggested a detection threshold of approximately 100 femptomoles for small localized objects. Experiments to assess the instrument's spatial resolution demonstrated the ability of the system to resolve objects placed at clear distances of less than 1 mm. This is a significant resolution increase over previously developed systems for animal imaging, and is primarily due to the large dataset employed and the use of inversion methods. Finally, the in vivo imaging capacity is showcased. It is expected that the large dataset collected can enable superior imaging of molecular probes in vivo and improve quantification of fluorescence signatures.
目前大多数为使用漫射光子对完整组织进行断层扫描研究而开发的成像系统，都存在光源和探测器数量有限的问题。在本文中，我们描述了一种用于小动物荧光成像的大数据集、低噪声断层扫描系统的构建与评估。该系统由一个平行板成像室和一个镜头耦合电荷耦合器件（CCD）相机组成，既能够进行传统的平面成像，也能够进行荧光断层扫描。平面成像数据用于指导获取包含超过106次测量的荧光分子断层扫描（FMT）数据集，并将解剖特征与断层扫描结果叠加，以改善视觉呈现效果。实验测量结果与用于预测光在成像室内传播的扩散理论模型吻合良好。对该仪器在三维空间中定量重建荧光染料分布能力的测试表明，实际荧光染料浓度与FMT结果之间的误差小于5%，并表明对于小的局部物体，检测阈值约为100飞摩尔。评估该仪器空间分辨率的实验证明，该系统能够分辨放置在小于1毫米清晰距离处的物体。这比之前开发的动物成像系统的分辨率有了显著提高，这主要归功于所采用的大数据集和反演方法的使用。最后，展示了其体内成像能力。预计所收集的大数据集能够实现对体内分子探针的卓越成像，并改善荧光信号的定量分析。
