Abstract
Diffuse correlation spectroscopy (DCS) is a non-invasive optical technique capable of monitoring tissue perfusion. The normalized temporal intensity autocorrelation function generated by DCS is typically characterized by assuming that the movement of erythrocytes can be modeled as a Brownian diffusion-like process instead of by the expected random flow model. Recently, a hybrid model, referred to as the hydrodynamic diffusion model, was proposed, which combines the random and Brownian flow models. The purpose of this study was to investigate the best model to describe autocorrelation functions acquired directly on the brain in order to avoid confounding effects of extracerebral tissues. Data were acquired from 11 pigs during normocapnia and hypocapnia, and flow changes were verified by computed tomography perfusion (CTP). The hydrodynamic diffusion model was found to provide the best fit to the autocorrelation functions; however, no significant difference for relative flow changes measured by the Brownian and hydrodynamic diffusion models was observed.
Highlights
Near-infrared spectroscopy (NIRS) methods based on the quantification of light absorption at specific wavelengths have been developed for measuring key physiological parameters, such as tissue perfusion, blood volume and oxygenation [1,2,3]
The isoflurane was reduced to 3-4% and the animal was transported to the computed tomography (CT) suite where the experiments were conducted using a portable NIRS/diffuse correlation spectroscopy (DCS) system
Eleven juvenile pigs were used in the study with an average weight of 16.0 ± 0.7 kg; only nine animals were scanned by computed tomography perfusion (CTP) due to limited access to the CT scanner for the first two experiments
Summary
Near-infrared spectroscopy (NIRS) methods based on the quantification of light absorption at specific wavelengths have been developed for measuring key physiological parameters, such as tissue perfusion, blood volume and oxygenation [1,2,3]. An alternative approach that provides continuous blood flow monitoring is diffuse correlation spectroscopy (DCS) [3]. This method indirectly measures changes in blood flow by monitoring light intensity fluctuations caused by the movement of erythrocytes in tissue [7,8]. Blood flow is assessed by characterizing light intensity decorrelation using a model that describes the movement of erythrocytes
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