This fNIRS method involves acquiringmultiple measurements of light at differing source-detector separationspositioned over a large area of tissue simultaneously or in rapid succession. Consequently, as the different separations penetrate tissue at differentdepths, optical tomography can measure cortical activation in 3-D space. Tomeasure the whole brain, this method is inherently restricted by thepenetration depth and reflectance of the light from source to detector. Therefore, a full 3-D image can only be measured in preterm or neonate infants with a smallhead and relatively transparent tissue properties of near-infrared light.
See Functional near-red infrared spectroscopy, Newborn, Optical imaging, Preterm infant