Multispectral imaging of absorption and scattering properties ofin vivoexposed rat brain using a digital red-green-blue camera

Abstract

Abstract. In order to estimate multispectral images of the absorption and scattering properties in the cerebral cortex of in vivo rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital RGB camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentrations of oxygenated hemoglobin and that of deoxygenated hemoglobin were estimated as the absorption parameters, whereas the coefficient a and the exponent b of the reduced scattering coefficient spectrum approximated by a power law function were estimated as the scattering parameters. The spectra of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters, and the spectral images of absorption and reduced scattering coefficients were then estimated. In order to confirm the feasibility of this method, we performed in vivo experiments on exposed rat brain. The estimated images of the absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. The changes in the estimated absorption and scattering parameters during normoxia, hyperoxia, and anoxia indicate the potential applicability of the method by which to evaluate the pathophysiological conditions of in vivo brain due to the loss of tissue viability. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Multispectral imaging of cortical vascular and hemodynamic responses to a shock wave: observation of spreading depolarization and oxygen supply-demand mismatch

“…The method is basically the same as that used in our previous study. 19,21 Figure 2 shows the flow diagram of the method. Absorbance spectrum AðλÞ was calculated from diffuse reflectance rðλÞ based on the following equation:…”

“…In this study, we performed multispectral imaging of the cortex of the rat brain that was transcranially exposed to an LISW and quantified two-dimensional cerebral hemodynamics and tissue scattering parameters using multiple regression analysis aided by Monte Carlo simulation for the spectral data obtained. 18,19 We assessed morphological changes of vessels and visualized distributions of regional hemoglobin concentration (rC Hb ) and tissue oxygen saturation (StO 2 ) for three time regimes: (i) just after LISW application (before the start of CSD), (ii) during CSD propagation, and (iii) after CSD propagation. Importantly, vascular type-dependent behaviors were observed, and the results were therefore analyzed for each vascular type (arteriolar, venular, and capillaries).…”

Near‐infrared diffuse reflectance signals for monitoring spreading depolarizations and progression of the lesion in a male rat focal cerebral ischemia model

“…As for the related cellular morphological changes in response to NIR reflectance signal changes, the microstructure of the cortex will be observed by electron microscopy, which enables estimation of scatterer size and, hence, light-scattering properties in the cortex. For estimation of the related light-scattering properties, we will use simulationbased quantitative analysis of both light absorption and scattering properties in the tissue (Yoshida et al, 2015), for which the recent advanced interferometric NIR spectroscopic technique is also applicable (Borycki, Kholiqov, & Srinivasan, 2017). The stroke model used in this study is for permanent focal ischemia, and we will perform experiments with an ischemia-reperfusion model to reveal the reversibility of the NIR reflectance signal and tissue viability, especially in the peripheral region of the ischemic center (penumbra).…”

Three‐dimensional microvascular network reconstruction from in vivo images with adaptation of the regional inhomogeneity in the signal‐to‐noise ratio

“…Specifically, for 2PLSM angiograms, this limitation is exaggerated due to the anatomical features of the vasculature, which runs three-dimensionally (3D) with different sizes of the vessels through tissue whose optical properties vary depending on regional scattering and absorption effects. [22][23][24][25][26] Therefore, application of conventional methods for region of interest-based segmentation to brain cells to adapt images with variable signal-to-noise ratios (SNRs) is not beneficial for accurately extracting a whole network of the vasculature in a consistent manner.…”