Estimation of the correlation amplitude of rf signals: application to microcirculation study

For the measurement of blood flow, signal processing based on temporal shift evaluation by cross-correlation of the RF signals is now widely used. The estimation of the normalized correlation coefficient is becoming a complementary tool. In the case of microcirculation (low flow rate, low SNR), the amplitude of the correlation peak can be used to detect the presence of blood flow and to discriminate between false and true detections (reliability index). We have numerically evaluated some statistical performances (bias and variance) of the cross-correlation algorithm used as a correlation peak amplitude estimator in severe conditions (short correlation window length, low SNR). Some of these results have been verified with in-vitro experimentation on a microcirculatory phantom and with in-vivo experimentation on the auriculares candales vein of the external ear of a rabbit.