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Journal of Biomedical Optics • Open Access

Phasor representation of oxy- and deoxyhemoglobin concentrations: what is the meaning of out-of-phase oscillations as measured by near-infrared spectroscopy?
Author(s): Feng Zheng; Angelo Sassaroli; Sergio Fantini

Paper Abstract

We propose a phasor representation for oscillations at a given frequency (or relatively narrow frequency band) of hemoglobin concentrations in tissue, as well as hemoglobin concentrations measured by near-infrared spectroscopy. This representation provides a straightforward visualization of the phase relationships between oscillations of oxy-, deoxy-, and total hemoglobin concentrations ([HbO], [Hb], and [HbT], respectively). We observe that measured oscillations of [Hb] and [HbO] with a phase difference that is neither 0 nor must result from the combination of different physiological processes that are out of phase (or time shifted) with respect to each other. Finally, we propose the use of cross-correlation phasors to map phase relationships and correlation levels among hemoglobin oscillations measured at spatially distinct locations at a given frequency. Such a representation may find a natural application in the study of functional connectivity networks in the brain.

Paper Details

Date Published: 1 July 2010
PDF: 3 pages
J. Biomed. Opt. 15(4) 040512 doi: 10.1117/1.3483466
Published in: Journal of Biomedical Optics Volume 15, Issue 4
Show Author Affiliations
Feng Zheng, Tufts Univ. (United States)
Angelo Sassaroli, Tufts Univ. (United States)
Sergio Fantini, Tufts Univ. (United States)

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