Evaluation of spatial distribution of skin blood flow using optical imaging

The utilization of optical imaging for the analysis and modeling of microcirculatory flow patterns is raising significant interest. This work focuses on the analysis of the alterations in the spatial distribution of blood flow caused by exposing the skin at a variable temperature. In optical imaging, the measurement of local perfusion at pixel level is not reliable because of the very low signal to noise ratio (SNR) of the resulting signal. To cope with this limitation, a reference signal of pulsatile blood flow is computed by averaging a large region of skin, thus obtaining an improved SNR. Then, for each pixel, we estimate the time shift between the local blood pulse wave and the reference signal, evaluating the peak of the correlation function between the two signals. An image representing the spatial distribution of the time delay is thus created.Textural parameters derived from cooccurrence matrices and from fractal analysis show that both skin heating and cooling produce alterations of the spatial distribution of blood perfusion.