Commercial laser Doppler perfusion monitors are calibrated using the perfusion value, i.e. the first order moment of the
Doppler power spectrum, from a measurement in a standardized microsphere colloidal suspension under Brownian
motion. The calibration perfusion value depends on several parameters of the suspension that are difficult to keep
constant with adequate accuracy, such as the concentration, temperature and the microsphere size distribution. The
calibration procedure itself may therefore introduce significant errors in the measured values.
An altered calibration procedure, where the zero order moment is used is described and demonstrated in this paper. Since
the above mentioned parameters only affect the frequency content of the Doppler power spectrum and not the total
power, the zero order moment will be independent of those parameters. It is shown that the variation in the calibration
value, as given by measurements on different scattering liquids with a wide range of scattering properties and
temperatures, is only a few percent using the proposed method. For the conventional calibration procedure, this variation
corresponds to an error introduced by merely a 1°C variation in the reference liquid temperature. The proposed
calibration method also enables absolute level comparisons between measured and simulated Doppler power spectra.