On velocity estimation using speckle decorrelation

Quantitative estimation of blood velocity using Doppler techniques is funda mentally limited because only the axial component can be detected. Speckle decorrelation resulting from scatterer motion may be used to compute non-ax ial components and to obtain quantitative flow information. Based on both s imulations and experimental results, it is shown that the decorrelation tec hnique is feasible only for constant flows. If flow gradients are present, the correlation between two signals along the same line of observation may be significantly affected by the gradients. Therefore, the decorrelation me thod cannot be used for quantitative flow estimation if flow gradients are not accurately measured and effects on signal correlation are not fully com pensated. Results in this paper show that accurate estimation of flow gradi ents is practically difficult. It is further shown that effects of signal-t o-noise ratio (SNR) on the correlation must also be taken into account for quantitative flow analysis.