Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy

Authors: HALLACOGLU, BERTAN - Tufts University; SASSAROLI, ANGELO - Tufts University; WYSOCKI, MICHAEL - Mount Sinai School Of Medicine; GUERRERO-BERROA, ELIZABETH - Mount Sinai School Of Medicine; SCHNAIDER BEERI, MICHAL - Mount Sinai School Of Medicine; HAROUTUNIAN, VAHRAM - Mount Sinai School Of Medicine; SHAUL, MERAV - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; ROSENBERG, IRWIN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; TROEN, ARON - Hebrew University Of Jerusalem; FANTINIA, SERGIO - Tufts University

Submitted to: Journal of Biomedical Optics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2012
Publication Date: 8/17/2012
Citation: Hallacoglu, B., Sassaroli, A., Wysocki, M., Guerrero-Berroa, E., Schnaider Beeri, M., Haroutunian, V., Shaul, M., Rosenberg, I.H., Troen, A.M., Fantinia, S. 2012. Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy. Journal of Biomedical Optics . 17(8):081406-1.

Interpretive Summary: Age remains the strongest risk factor for developing cognitive decline and dementia. Changes in the anatomy of the brain’s blood vessels are common in dementia and have been suggested to contribute to the development, and affect the severity of, age-related cognitive decline. Near Infrared Spectroscopy (NIRS) is a technique measuring the amount of blood and oxygen supplied to tissues such as the brain. Our study included measurements on 36 healthy elderly and 19 young adults , and recorded a significant decrease in the amount of blood and oxygen levels supplied to the brain between the two age groups, providing interesting insight into physiological changes in the brain that occur over time. Also, measurements taken five months apart in 16 of the elderly volunteers demonstrated the reliability and reproducibility of these measurements. This is one of the few studies to describe absolute amounts of blood and oxygen delivered to the brain in young vs. elderly subjects using cerebral NIRS measurements. This represents a significant advance toward the application of NIRS to monitor long-term changes in cerebrovascular health.

Technical Abstract: We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85 ± 6 years) and 19 young adults (mean age, 28 ± 4 years). Non-invasive measurements were obtained on the forehead using a commercially available multi-distance frequency-domain system and analyzed using a diffusion theory model for a semi-infinite, homogeneous medium with semi-infinite boundary conditions. Our study included repeat measurements, taken five months apart, on 16 elderly volunteers that demonstrate intra-subject reproducibility of the absolute measurements with cross-correlation coefficients of 0.9 for absorption coefficient (ua), oxy-hemoglobin concentration ([HbO2]), and total hemoglobin concentration ([HbT]), 0.7 for deoxy-hemoglobin concentration ([Hb]), 0.8 for hemoglobin oxygen saturation (StO2), and 0.7 for reduced scattering coefficient (u's). We found significant differences between the two age groups. Compared to young subjects, elderly subjects had lower cerebral [HbO2], [Hb], [HbT], and StO2 by 10 ± 4 uM, 4 ± 3 uM, 14 ± 5 uM, and 6%±5%, respectively. Our results demonstrate the reliability and robustness of multi-distance near-infrared spectroscopy measurements based on a homogeneous model in the human forehead on a large sample of human subjects. Absolute, non-invasive optical measurements on the brain, such as those presented here, can significantly advance the development of NIRS technology as a tool for monitoring resting/basal cerebral perfusion, hemodynamics, oxygenation, and metabolism.