Abstract Details

Title Optical Properties and Oximetry Parameters of Cerebral Atrophic and Normal Regions in Healthy Volunteers

Topic Aging, Dementia, and Behavioral Neurology

Presentation(s) P5 - Poster Session 5 (5:30 PM-6:30 PM)

Poster/Presentation
Number 9-018

Objective It is not known if brain atrophy can affect optical properties and cerebral oximetry results as measured by Time-Domain Near Infrared Spectroscopy (TD-NIRS).

Background Cerebral Time-Domain Near Infrared Spectroscopy (TD-NIRS) provides reproducible absolute absorption and scattering coefficients, haemoglobin species’ concentration and tissue oxygen saturation (StO₂) in the cerebral outer layers.

Design/Methods TD-NIRS measurements were performed on healthy volunteers on multiple head regions. We measured absorption and scattering coefficients (μa, μ_s'), hemoglobin species concentration and oxygen saturation (StO₂). According to neuroimaging investigations with fiducial markers, we classified the brain area underlying each TD-NIRS probe as “atrophic” or “normal” region. Regional cerebral atrophy was defined according to Global Cortical Atrophy (GCA) rating scale.

Results We analyzed 50 healthy volunteers (age 64.0±14.9). The mean values of absorption coefficients, hemoglobin species and StO₂ were comparable between atrophic and normal cerebral regions. We observed significantly lower mean values of μ_s’ at 690 nm wavelength in atrophic areas compared to normal regions (7.374 (±1.232) vs. 8.279 (±0.974) cm^-1, p=0.008]. In binomial logistic regression analysis together with age, μ_s’(690) was independently associated with atrophy (beta=0.45, CI 95% 0.24-0.86, p=0.015). A cut-off of μ_s’(690) <7.5 cm^-1 had a sensitivity of 86% and specificity of 58% in correctly predicting atrophic areas (AUC 71.2%, CI 95% 54.2%-88.2%).

Conclusions In our cohort, atrophic and normal regions displayed comparable values of absorption coefficients, haemoglobin species and StO₂, but significantly lower scattering coefficient at 690 nm wavelength. These results might be consistent with the presence in atrophic region of a ticker layer of cerebrospinal fluid, which has a lower density compared to brain tissue, while the concentration of haemoglobin species in the microcirculation is not affected. This finding might suggest that reduced scattering coefficient might be explored as a surrogate marker of cerebral atrophy.

Authors/Disclosures
PRESENTER	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file

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