Blaney Giles, Sassaroli Angelo, Fantini Sergio
Department of Biomedical Engineering, Tufts University, Medford, Massachusetts 02155, USA.
Rev Sci Instrum. 2020 Sep 1;91(9):093702. doi: 10.1063/5.0015512.
We recently proposed a dual-slope technique for diffuse optical spectroscopy and imaging of scattering media. This technique requires a special configuration of light sources and optical detectors to create dual-slope sets. Here, we present methods for designing, optimizing, and building an optical imaging array that features m dual-slope sets to image n voxels. After defining the m × n matrix (S) that describes the sensitivity of the m dual-slope measurements to absorption perturbations in each of the n voxels, we formulate the inverse imaging problem in terms of the Moore-Penrose pseudoinverse matrix of S (S). This approach allows us to introduce several measures of imaging performance: reconstruction accuracy (correct spatial mapping), crosstalk (incorrect spatial mapping), resolution (point spread function), and localization (offset between actual and reconstructed point perturbations). Furthermore, by considering the singular value decomposition formulation, we show the significance of visualizing the first m right singular vectors of S, whose linear combination generates the reconstructed map. We also describe methods to build a physical array using a three-layer mesh structure (two polyethylene films and polypropylene hook-and-loop fabric) embedded in silicone (PDMS). Finally, we apply these methods to design two arrays and choose one to construct. The chosen array consists of 16 illumination fibers, 10 detection fibers, and 27 dual-slope sets for dual-slope imaging optimized for the size of field of view and localization of absorption perturbations. This particular array is aimed at functional near-infrared spectroscopy of the human brain, but the methods presented here are of general applicability to a variety of devices and imaging scenarios.
我们最近提出了一种用于散射介质的漫射光学光谱和成像的双斜率技术。该技术需要光源和光学探测器的特殊配置来创建双斜率集。在此，我们介绍设计、优化和构建具有(m)个双斜率集以对(n)个体素进行成像的光学成像阵列的方法。在定义了描述(m)次双斜率测量对(n)个体素中每个体素吸收扰动的灵敏度的(m×n)矩阵((S))之后，我们根据(S)的摩尔 - 彭罗斯伪逆矩阵((S))来表述逆成像问题。这种方法使我们能够引入几种成像性能度量：重建精度（正确的空间映射）、串扰（错误的空间映射）、分辨率（点扩散函数）和定位（实际和重建点扰动之间的偏移）。此外，通过考虑奇异值分解公式，我们展示了可视化(S)的前(m)个右奇异向量的重要性，其线性组合生成重建图。我们还描述了使用嵌入硅酮（PDMS）中的三层网格结构（两层聚乙烯薄膜和聚丙烯钩环织物）构建物理阵列的方法。最后，我们应用这些方法设计两个阵列并选择一个进行构建。所选阵列由16根照明光纤、10根检测光纤和27个双斜率集组成，用于针对视野大小和吸收扰动定位进行优化的双斜率成像。这个特定的阵列旨在用于人类大脑的功能近红外光谱，但这里介绍 的方法普遍适用于各种设备和成像场景。
