Using NIR spatial illumination for detection and mapping chromophore changes during cerebral edema

Abstract

We used spatially-modulated near-infrared (NIR) light to detect and map chromophore changes during cerebral edema in the rat neocortex. Cerebral edema was induced by intraperitoneal injections of free water (35% of body weight). Intracranial pressure (ICP) was measured with an optical fiber based Fabry-Perot interferometer sensor inserted into the parenchyma of the right frontal lobe during water administration. Increase in ICP from a baseline value of 10 cm-water to 145 cm-water was observed. Following induction of cerebral edema, there was a 26±1.7% increase in tissue concentration of deoxyhemoglobin and a 47±4.7%, 17±3% and 37±3.7% decrease in oxyhemoglobin, total hemoglobin concentration and cerebral tissue oxygen saturation levels, respectively. To the best of our knowledge, this is the first report describing the use of NIR spatial modulation of light for detecting and mapping changes in tissue concentrations of physiologic chromophores over time in response to cerebral edema.

Closed head injury-induced changes in brain pathophysiology assessed with near-infrared structured illumination in a mouse model

“…As stated above, this behavior demonstrates the morphologic changes that occurred in the brain during CHI and highlights the presence of cellular swelling within brain parenchyma. 10,43,[56][57][58] For completeness of scattering processing, we next present qualitative image maps of both A and sp. At this point, we have a spectral cube with dimensions of 200 × 200 × 6, where 200 × 200 is the 2-D image pixel size and 6 stands for the number of the wavelengths used.…”

“…28 As will be detailed in Secs. 2.3 to 2.5, the present study differs from previous reported structured illumination methods [9][10][11][12][13][14]27,28 in the simplicity in the way the optical properties were obtained (using high-and low-spatial frequencies) and in the calibration procedure. Out of these, for the reader's knowledge, the use of sinusoidal pattern is also popular as a super-resolution platform, 29 in machine vision, 30 and in the area of optical image processing, specifically when three-dimensional (3-D) object surfaces measuring (profilometery) is on-demand.…”

“…The present work is part of a series of studies applying projection of near-infrared (NIR) structured illumination to study brain pathophysiology during brain injury in anesthetized rodents. [9][10][11][12][13][14] This, a relatively new large field-of-view optical imaging modality, uses a sinusoidal grid pattern to separately map tissue absorption (μ a ) and reduced light scattering (μ 0 s ) properties of turbid medium such as biological samples in a noncontact and scan-free manner. 15 This separation enables accurate quantification of tissue's biochemical compositions (related to light absorption) and structural properties (related to light scattering) and thus provides a better comprehensive understanding and characterization of the corresponding tissue properties.…”

Noninvasive assessment of hemodynamic and brain metabolism parameters following closed head injury in a mouse model by comparative diffuse optical reflectance approaches

“…35 Over recent decades, several studies have described the instrumentation of spatially modulated illumination and its use in noncontact and scan-free imaging in a variety of biomedical applications [36][37][38][39][40][41][42] and in the clinic. 43 Spatially modulated illumination is a multispectral wide-field imaging modality that utilizes NIR periodic illumination patterns with sinusoidal frequencies of up to 0.5 mm −1 to separately derive and spatially map the absolute values of the optical properties of tissue, i.e., absorption (μ a ) and reduced light scattering (μ 0 s ) coefficients of turbid media.…”

Effect of Spatial Modulated Light on Position of Self-Calibration Point

“…Optimization of the frequency parameter was reported by Bodenschatz [6] and Hu [12] for spatial frequency imaging of biological materials. The widespread use of spatial modulation for mapping turbid media in different optical techniques, with its potential applications in human disease (ischemic stroke [10], Alzheimer's disease [11] and cerebral edema [13], etc. ), led us to examine the modulation effect on our method.…”