Spatial Coregistration of Functional Near-Infrared Spectroscopy to Brain MRI

Traditional neuroimaging techniques restrict movement and make it difficult to study the processes that require oral, upper limb, or lower limb motor execution. Functional near-infrared spectroscopy (fNIRS) is an optical neuroimaging modality that measures brain oxygenation and permits movement during data acquisition. A key limitation of fNIRS, however, is the lack of a standard method to coregister quantitative fNIRS measurements to structural images such as magnetic resonance imaging (MRI). Additionally, fNIRS-MRI coregistration studies have not been reported in older adults.

fNIRS and structural MRI were acquired from 30 nondemented older adults. Sixteen fNIRS channels that assess hemodynamic changes in the prefrontal cortex (PFC; an area crucial in various age-related processes) were coregistered to structural MRI. Vitamin E capsules were used to mark the locations of fNIRS detectors and light sources on the scalp. We used the balloon-inflation algorithm to project fNIRS channel locations on the scalp to underlying cortical surface.

We provide coordinates for the 16 fNIRS channels in the PFC on the cortical surface in both MNI and Talairach spaces, with minimal variability that is within the spatial resolution of our fNIRS system.

Our study provides useful spatial information for stand-alone fNIRS data in future studies, particularly investigations in age-related processes.