1 May 2008 Measurement of layer-like hemodynamic trends in scalp and cortex: implications for physiological baseline suppression in functional near-infrared spectroscopy
Author Affiliations +
J. of Biomedical Optics, 13(3), 034017 (2008). doi:10.1117/1.2940587
Abstract
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 33 mm away, and one with detectors collinear with the source (5 to 33 mm 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 5 mm 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.
Rolf B. Saager, Andrew J. Berger, "Measurement of layer-like hemodynamic trends in scalp and cortex: implications for physiological baseline suppression in functional near-infrared spectroscopy," Journal of Biomedical Optics 13(3), 034017 (1 May 2008). http://dx.doi.org/10.1117/1.2940587
JOURNAL ARTICLE
10 PAGES


SHARE
KEYWORDS
Hemodynamics

Near infrared spectroscopy

Sensors

Brain

Signal detection

Head

Visualization

Back to Top