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Research Papers

Measurement of layer-like hemodynamic trends in scalp and cortex: implications for physiological baseline suppression in functional near-infrared spectroscopy

[+] Author Affiliations
Rolf Saager, Andrew Berger

University of Rochester, The Institute of Optics, Goergen Hall 405, Rochester, New York 14627

J. Biomed. Opt. 13(3), 034017 (June 24, 2008). doi:10.1117/1.2940587
History: Received July 19, 2007; Revised November 13, 2007; Accepted December 17, 2007; Published June 24, 2008
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A multidetector, continuous wave, near-infrared spectroscopy (NIRS) system is developed to examine whether the hemodynamics of the scalp and brain in adults contain significant layer-like hemodynamic trends. NIRS measurements are made using contrasting geometries, one with four detectors equidistant from a source 33mm away, and one with detectors collinear with the source (5 to 33mm away). When NIRS time series are acquired over the prefrontal cortex from resting adults using both geometries, variations among the time series are consistent with a substantially homogeneous two-layer model (p<0.001) and inconsistent with one dominated by heterogeneities. Additionally, when time series measured 5mm from the source are subtracted from corresponding 33-mm signals via a least-squares algorithm, 60% of the hemoglobin changes are on average removed. These results suggest that hemodynamic trends present in the scalp can contribute significantly to NIRS measurements, and that attempts to reduce this noise by subtracting a simultaneous near-channel measurement using a two-layer model are justified. Such subtractions are then performed on NIRS measurements from two stimulus protocols. For systemic stimulations (Valsalva maneuver), the subtraction cancels the hemodynamic response, as desired. For localized stimulation of the occipital lobe (viewing a flickering pattern), the subtraction isolated a stimulus-correlated hemodynamic feature from background noise.

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© 2008 Society of Photo-Optical Instrumentation Engineers

Citation

Rolf Saager and Andrew Berger
"Measurement of layer-like hemodynamic trends in scalp and cortex: implications for physiological baseline suppression in functional near-infrared spectroscopy", J. Biomed. Opt. 13(3), 034017 (June 24, 2008). ; http://dx.doi.org/10.1117/1.2940587


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