Dynamic mapping of the human brain by time-resolved nirs techniques

Abstract

Dynamic mapping of the human brain by time-resolved near-infraredspectroscopy (trNIRS), or functional NIRS (fNIRS), is based on the injection of picosecond or sub-nanosecond laser pulses into the head and the measurement of the pulse shape and the intensity after diffusion through the tissue. By analysing the pulse shape and the intensity of the signals at different detector and source positions and different wavelengths, changes in the oxy- and deoxy-haemoglobin concentration are obtained for extracerebral and intracerebral tissue layers and for different depth in the brain. The technique can by combined with the injection of a bolus of an exogenous absorber. By recording either absorption or fluorescence, the in- and outflow of the absorber in different brain compartments can be monitored. The inand outflow dynamics reveal differences in the blood flow caused by impaired