Spatially weighted BOLD signal for comparison of functional magnetic resonance imaging and near-infrared imaging of the brain

We introduce a weighted spatial average of the functional magnetic resonance imaging (fMRI) BOLD signal (blood oxygen level-dependent) that is appropriate for comparison with the changes in oxy- and deoxy-hemoglobin concentrations measured with near-infrared spectroscopy (NIRS) during brain activati...

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Bibliographic Details
Published inNeuroImage (Orlando, Fla.) Vol. 33; no. 2; pp. 505 - 514
Main Authors Sassaroli, Angelo, Frederick, Blaise deB, Tong, Yunjie, Renshaw, Perry F., Fantini, Sergio
Format Journal Article
LanguageEnglish
Published United States Elsevier Inc 01.11.2006
Elsevier Limited
Subjects
Brain
Brain - anatomy & histology
Brain Mapping
Cerebrovascular Circulation
Functional Laterality
Hand - innervation
Humans
Magnetic Resonance Imaging - methods
NMR
Nuclear magnetic resonance
Oxygen - blood
Photons
Spectrophotometry, Infrared - methods
Studies
Veins & arteries
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Summary:We introduce a weighted spatial average of the functional magnetic resonance imaging (fMRI) BOLD signal (blood oxygen level-dependent) that is appropriate for comparison with the changes in oxy- and deoxy-hemoglobin concentrations measured with near-infrared spectroscopy (NIRS) during brain activation. Because the BOLD signal shows a spatial dependence (both in shape and amplitude) within the region of activation, the location of the optical probe with respect to the region of BOLD activation should be taken into account for comparison of the BOLD and NIRS signals. Our new method is based on combining weighted contributions of the BOLD signal from each activated voxel, with a weight given by a hitting density function for photons migrating between a given pair of illumination and collection points. We present a case study where we have found that the new spatially weighted BOLD signal shows a high spatial and temporal correlation with the oxy- and deoxy-hemoglobin concentration changes measured with NIRS during a hand-tapping protocol. These findings reinforce the idea that fMRI and NIRS are sensitive to similar underlying hemodynamic changes, and indicate that the proposed weighted BOLD signal is needed for a quantitative comparison of BOLD and NIRS signals.
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ISSN:1053-8119
1095-9572
DOI:10.1016/j.neuroimage.2006.07.006