An explanation for the effectiveness of the ‘Draijer’ algorithm for high speed laser Doppler perfusion imaging

Laser Doppler flowmetry relies upon the use of the first moment of the power spectrum of the photocurrent and numerous methods of providing an estimate of this have been implemented. One, operating in the time domain and using only a few, simple processing steps, is claimed to be both fast and accurate (Draijer et al. in Med Biol Eng Comput 47(10):1103–1109, 2009 ). However, it is acknowledged that the theory underpinning its operation is intuitive. Here it is shown that this algorithm mimics the use of the analytic representation of the photocurrent and although capable of approximating the required value is certainly not equivalent mathematically.