Callaghan Innovation Research Papers

Back to Research Papers

TitleMeasuring Doppler-like power spectra and dermal perfusion using laser speckle contrast with multiple exposures
Publication TypeConference Paper
Year of Publication2010
AuthorsThompson, O.B., and Andrews M.K.
Conference NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Date Published2010
KeywordsArterial occlusions, Autocorrelation, Autocorrelation functions, Blood flow, Brownian motion, Brownian movement, Classifiers, Clinical application, computer simulation, Doppler, Doppler effect, Experimental measurements, Human tissues, Laser doppler, Laser Doppler systems, Laser speckle, Laser speckle contrast, Light, Light fluctuation, Light intensity, Multiple exposure, Optical systems, Perfusion images, Power spectrum, Power-spectra, Regression analysis, Scanning lasers, Speckle, Spectral density, Spectral information
AbstractLaser speckle contrast measurements provide effectively instantaneous maps of dermal perfusion, using easily obtainable hardware, but such maps are qualitative. Clinical applications of these techniques require a good theoretical and experimental foundation of understanding before relating them to a physiologically significant, quantitative perfusion value. We have confirmed that multiple-exposure laser speckle methods produce the same spectral information as laser Doppler measurements when applied to targets such as human tissue with embedded moving scatterers. This confirmation is based on both computer simulation of laser speckle data and experimental measurements on Brownian motion and skin perfusion using a laser Doppler system and a multiple-exposure laser speckle system. The Power Spectral Density (PSD) measurements of the light fluctuations derived using both techniques are equivalent. Dermal perfusion images can therefore be measured in exactly equivalent terms by either laser speckle contrast or more laborious scanning laser Doppler methods. Most analyses relating laser speckle contrast to perfusion depend on assuming a particular temporal autocorrelation function for the light intensity fluctuations in biospeckle. Using multiple-exposure laser speckle allows the autocorrelation function to be measured rather than assumed. Measured autocorrelation functions and their related power spectra for dermal perfusion are presented, including measurements under arterial occlusion to investigate a 'biological zero': the speckle blur relating to the remaining movement of tissue constituents when there is no net blood flow. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Back to top