title: Pressure modulation algorithm to separate cerebral hemodynamic signals from extracerebral artifacts.
abstract: We introduce and validate a pressure measurement paradigm that reduces extracerebral contamination from superficial tissues in optical monitoring of cerebral blood flow with diffuse correlation spectroscopy (DCS). The scheme determines subject-specific contributions of extracerebral and cerebral tissues to the DCS signal by utilizing probe pressure modulation to induce variations in extracerebral blood flow. For analysis, the head is modeled as a two-layer medium and is probed with long and short source-detector separations. Then a combination of pressure modulation and a modified Beer-Lambert law for flow enables experimenters to linearly relate differential DCS signals to cerebral and extracerebral blood flow variation without a priori anatomical information. We demonstrate the algorithm's ability to isolate cerebral blood flow during a finger-tapping task and during graded scalp ischemia in healthy adults. Finally, we adapt the pressure modulation algorithm to ameliorate extracerebral contamination in monitoring of cerebral blood oxygenation and blood volume by near-infrared spectroscopy.
authors: University of Pennsylvania , Department of Physics and Astronomy, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
authors: Wesley B
authors: WB
authors: Baker
authors: University of Pennsylvania , Department of Physics and Astronomy, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
authors: Ashwin B
authors: AB
authors: Parthasarathy
authors: University of Pennsylvania , Department of Physics and Astronomy, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
authors: Tiffany S
authors: TS
authors: Ko
authors: University of Pennsylvania , Department of Physics and Astronomy, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States ; Children's Hospital of Philadelphia , Division of Neurology, 3401 Civic Center Boulevard, Philadelphia, Pennsylvania 19104, United States.
authors: David R
authors: DR
authors: Busch
authors: University of Pennsylvania , Department of Physics and Astronomy, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
authors: Kenneth
authors: K
authors: Abramson
authors: University of Pennsylvania , Department of Physics and Astronomy, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States ; National Cheng Kung University , Department of Photonics, No. 1, University Road, Tainan City 701, Taiwan.
authors: Shih-Yu
authors: SY
authors: Tzeng
authors: University of Campinas , Institute of Physics, 777 R. Sergio Buarque de Holanda, Campinas 13083-859, Brazil.
authors: Rickson C
authors: RC
authors: Mesquita
authors: ICFO-Institut de Ciències Fotòniques , Mediterranean Technology Park, Av. Carl Friedrich Gauss 3, Castelldefels (Barcelona) 08860, Spain.
authors: Turgut
authors: T
authors: Durduran
authors: University of Pennsylvania , Department of Neurology, 3450 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States.
authors: Joel H
authors: JH
authors: Greenberg
authors: Hospital of the University of Pennsylvania , Department of Neurosurgery, 3400 Spruce Street, Philadelphia, Pennsylvania 19104, United States.
authors: David K
authors: DK
authors: Kung
authors: University of Pennsylvania , Department of Physics and Astronomy, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
authors: Arjun G
authors: AG
authors: Yodh
keywords: cerebral blood flow monitoring; diffuse correlation spectroscopy; functional brain imaging; near-infrared spectroscopy; stroke