A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy

Abstract

Continuous measurement of local brain oxygen saturation (SO ) can be used to monitor the status of brain trauma patients in the neurocritical care unit. Currently, micro-oxygen-electrodes are considered as the "gold standard" in measuring cerebral oxygen pressure (pO ), which is closely related to SO through the oxygen dissociation curve (ODC) of hemoglobin, but with the drawback of slow in response time. The present study suggests estimation of SO in brain tissue using diffuse reflectance spectroscopy (DRS) for finding an analytical relation between measured spectra and the SO for different blood concentrations. The P diffusion approximation is used to generate a set of spectra simulating brain tissue for various levels of blood concentrations in order to estimate SO . The algorithm is evaluated on optical phantoms mimicking white brain matter (blood volume of 0.5-2%) where pO and temperature is controlled and on clinical data collected during brain surgery. The suggested method is capable of estimating the blood fraction and oxygen saturation changes from the spectroscopic signal and the hemoglobin absorption profile.

Quantitative in vivo detection of adipose tissue browning using diffuse reflectance spectroscopy in near‐infrared II window

“…Diffuse reflectance spectroscopy (DRS) has been used for a number of biomedical applications including epithelial tissue characterization, brain study, breast cancer detection and surgical margin assessment, skin pigmentation research etc. [20][21][22][23][24][25][26][27][28] DRS has been preferred technique for its application in blood perfusion and tissue oxygenation studies within ultraviolet-visible wavelength range and researchers have extended these spectroscopic measurements range up to NIR (400-1600 nm) to include absorption from lipid and water chromophores. [29,30] It has been reported that extended NIR wavelength region measurement renders a better discrimination between benign and tumor sites as well as accurate estimation of chromophores present in the tissue.…”

Optical monitoring of cerebral microcirculation in neurointensive care

“…Software modules were in-house programmed in LabVIEW® (National Instruments Inc., USA) for recording and real-time display of signals generated by each system in the NICU [ 29 , 31 ]. The LDF software module contains features such as trend monitoring of the perfusion and TLI signals by averaging over a preselected time interval (e.g., 10, 20, 30, 60 s) and calculation of the heart rate (HR) as well as the pulsativity index (PI) (Fig.…”

“…The HR was estimated using a systolic peak finding algorithm with the LDF-generated perfusion signal and PI as the amplitude difference of the flow pulsations divided by the average signal over the selected interval [ 31 ]. The SO 2 in the tissue was estimated using an algorithm previously developed for use in human cerebral white matter [ 29 ] and evaluated using clinical data [ 28 ].…”

“…In this study, DRS was preferred over near-infrared spectroscopy (NIRS) in terms of its localized sampling volume through small optical fiber separations in the sensing probe and use of a wide wavelength range in the visible spectrum compared to only using a few wavelengths in the NIR region [ 6 ]. Examples of work for assessing human brain circulation with optics are Martini et al and Klein et al using white light spectroscopy and NIRS [ 18 , 21 ] or recent work using DRS [ 29 , 30 ].…”

Optical Monitoring Techniques for Navigation during Stereotactic Neurosurgery

“…(49) With the help of the oxygenated hemoglobin (HbO 2 ) and deoxygenated hemoglobin (Hb) spectra from brain tissue, an estimation of the oxygen saturation (SO 2 ) can be achieved by curve fitting to known absorption spectra. The present work in the Linköping group focuses on improving the oxygen saturation algorithm for in vivo on line recording in brain tissue (50) in relation to, for example, traumatic brain injury in the neuro-intensive care unit, and thus also adaptation and implementation of the methods for monitoring of both microcirculation (12) and tissue oxygenation during brain surgery. …”