title: Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy.
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 (μa), 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 (μ'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 μM, 4 ± 3 μM, 14 ± 5 μM, 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.
authors.affiliation: Tufts University, Department of Biomedical Engineering, 4 Colby St, Medford, MA 02155, USA. bertan.hallacoglu@tufts.edu
authors.forename: Bertan
authors.initials: B
authors.lastname: Hallacoglu
authors.forename: Angelo
authors.initials: A
authors.lastname: Sassaroli
authors.forename: Michael
authors.initials: M
authors.lastname: Wysocki
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Guerrero-Berroa
authors.forename: Michal
authors.initials: M
authors.lastname: Schnaider Beeri
authors.forename: Vahram
authors.initials: V
authors.lastname: Haroutunian
authors.forename: Merav
authors.initials: M
authors.lastname: Shaul
authors.forename: Irwin H
authors.initials: IH
authors.lastname: Rosenberg
authors.forename: Aron M
authors.initials: AM
authors.lastname: Troen
authors.forename: Sergio
authors.initials: S
authors.lastname: Fantini
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D000465:Algorithms; D001921:Brain / Q000378:metabolism*; D005260:Female; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D008297:Male; D010100:Oxygen / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D006454:Hemoglobins; D010100:Oxygen