title: In vivo cerebrovascular measurement combining diffuse near-infrared absorption and correlation spectroscopies.
abstract: We combine two near-infrared diffuse optical techniques to study variations of blood flow, haemoglobin concentration, and blood oxygen saturation in the functioning rat brain. Diffuse correlation spectroscopy (or flowmetry) monitors changes in the cerebral blood flow, without the use of the principles of tracer clearance, by measuring the optical phase-shifts caused by moving blood cells. Near-infrared absorption spectroscopy concurrently measures tissue absorption at two wavelengths to determine haemoglobin concentration and blood oxygen saturation in this same tissue volume. This optical probe is non-invasive and was employed through the intact skull. The utility of the technique is demonstrated in vivo by measuring the temporal changes in the regional vascular dynamics of rat brain during hypercapnia. Temporal and spatial variations of cerebral blood flow, haemoglobin concentration and blood oxygen saturation during hypercapnia are compared with other measurements in the literature, and a quantitative analysis demonstrating the self-consistency of our combined observations of vascular response is presented.
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: C
authors.initials: C
authors.lastname: Cheung
authors.forename: J P
authors.initials: JP
authors.lastname: Culver
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: J H
authors.initials: JH
authors.lastname: Greenberg
authors.forename: A G
authors.initials: AG
authors.lastname: Yodh
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D002540:Cerebral Cortex / Q000098:blood supply; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004912:Erythrocytes / Q000502:physiology; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007834:Lasers; D009412:Nerve Fibers / Q000502:physiology; D010100:Oxygen / Q000097:blood; D017785:Photons; D051381:Rats; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: D006454:Hemoglobins; D002245:Carbon Dioxide; D010100:Oxygen