Optical methods for blood perfusion measurement - Theoretical comparison among four different modalities

Blood perfusion in human tissue can be measured in vivo by means of various optical methods, which seem to be very different from one another. The most prominent examples of them are laser Doppler flowmetry, laser speckle contrast imaging, diffuse correlation spectroscopy, and the most recently developed diffuse speckle contrast analysis. In this paper, we claim that these four seemingly different modalities are examining different aspects of the same entity - the temporal autocorrelation function of scattered photons. We will show how the observables in each modality can be theoretically derived from the temporal autocorrelation function, and will discuss the merits and drawbacks of each modality in its practical use.