Signal and Image Processing Institute, Department of Electrical Engineering-Systems, University of Southern California, Los Angeles, CA 90089, USA.
Phys Med Biol. 2010 May 21;55(10):2961-82. doi: 10.1088/0031-9155/55/10/011. Epub 2010 Apr 30.
Fluorescence molecular tomography is a powerful tool for 3D visualization of molecular targets and pathways in vivo in small animals. Owing to the high degrees of absorption and scattering of light through tissue, the fluorescence tomographic inverse problem is inherently ill-posed. In order to improve source localization and the conditioning of the light propagation model, multiple sets of data are acquired by illuminating the animal surface with different spatial patterns of near-infrared light. However, the choice of these patterns in most experimental setups is ad hoc and suboptimal. This paper presents a systematic approach for designing efficient illumination patterns for fluorescence tomography. Our objective here is to determine how to optimally illuminate the animal surface so as to maximize the information content in the acquired data. We achieve this by improving the conditioning of the Fisher information matrix. We parameterize the spatial illumination patterns and formulate our problem as a constrained optimization problem that, for a fixed number of illumination patterns, yields the optimal set of patterns. For geometric insight, we used our method to generate a set of three optimal patterns for an optically homogeneous, regular geometrical shape and observed expected symmetries in the result. We also generated a set of six optimal patterns for an optically homogeneous cuboidal phantom set up in the transillumination mode. Finally, we computed optimal illumination patterns for an optically inhomogeneous realistically shaped mouse atlas for different given numbers of patterns. The regularized pseudoinverse matrix, generated using the singular value decomposition, was employed to reconstruct the point spread function for each set of patterns in the presence of a sample fluorescent point source deep inside the mouse atlas. We have evaluated the performance of our method by examining the singular value spectra as well as plots of average spatial resolution versus estimator variance corresponding to different illumination schemes.
荧光分子断层成像是一种强大的工具，可用于在小动物体内对分子靶标和途径进行 3D 可视化。由于光在组织中的高度吸收和散射，荧光断层成像逆问题本质上是不适定的。为了提高源定位和光传播模型的条件，通过用不同的近红外光空间模式照射动物表面来获取多组数据。然而，在大多数实验设置中，这些模式的选择是特定的和次优的。本文提出了一种用于设计荧光断层成像有效照明模式的系统方法。我们的目标是确定如何最佳地照射动物表面，以便最大限度地提高所获取数据的信息量。我们通过改进 Fisher 信息矩阵的条件来实现这一点。我们参数化空间照明模式，并将我们的问题表述为一个约束优化问题，对于固定数量的照明模式，该问题产生最佳的模式集。为了获得几何洞察力，我们使用我们的方法为具有光学均匀、规则几何形状的物体生成了一组三个最佳模式，并观察到结果中的预期对称性。我们还为设置在透射模式下的光学均匀立方体模型生成了一组六个最佳模式。最后，我们为具有不同给定模式数量的光学不均匀的真实形状的老鼠图谱计算了最佳照明模式。使用奇异值分解生成正则化伪逆矩阵，用于在老鼠图谱深处的荧光点源样本存在的情况下，对每组模式的点扩散函数进行重建。我们通过检查奇异值谱以及对应于不同照明方案的平均空间分辨率与估计器方差的图，评估了我们方法的性能。
