Spectral analysis of near-infrared spectroscopy signals measured from prefrontal lobe in subjects at risk for stroke
Schematics of tissue oxygenation detection with two detectors.
(a) Raw [HbO2] data, (b) the corresponding wavelet transform in the time-frequency plane and (c) the averaged spectrum of NIR signal shown on a log scale. The vertical lines indicate the outer limits of the frequency interval: (I) 0.005–0.02 Hz, (II) 0.02–0.06 Hz, (III) 0.06–0.15 Hz, (IV) 0.15–0.4 Hz, and (V) 0.4–2 Hz, which correspond to endothelial-related metabolic, neurogenic, myogenic, respiratory and cardiac activities, respectively.
Comparison of the amplitudes of cerebral NIR signal (a) [Hb], (b) [HbO2] and (c) [tHb] in the five frequency intervals between the normal subjects and the subjects at risk for stroke. (I) 0.005–0.02 Hz, (II) 0.02–0.06 Hz, (III) 0.06–0.15 Hz, (IV) 0.15–0.4 Hz, (V) 0.4–2 Hz. Significant differences are labelled between normal and risk *p < 0.05, **p < 0.01.
Characteristics of participants.
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