LASCA system calibration for single exposure time measurements

The Laser Speckle Contrast Analysis (LASCA) is a relatively simple method for blood flow monitoring in tissues. Although it is widely used for cerebral and retinal blood flow measurements, in case of skin the intensive light scattering from its surface is a considerable drawback of the method when using single exposure time measurements and the results can be only used for qualitative perfusion comparison in the course of one experiment. A wide exposure time range sampling procedure has been proposed to determine the real correlation time of the speckle intensity fluctuations (inversely proportional with the blood velocity), independently of the applied setup. This correlation time determination is based on completion of the theoretical exposure time-contrast function with two additional parameters and fitting of the so-obtained function to the contrast values measured for different exposure values. Since the recording and processing time is longer than that of single exposure measurements, our aim was to demonstrate that after an initial determination of the fitting parameters, these values can further be used for single exposure monitoring independently of the flow velocity.