EXPERIMENTAL EVALUATION OF VELOCITY AND POWER ESTIMATION FOR ULTRASOUND BLOOD-FLOW IMAGING, BY MEANS OF A 2-DIMENSIONAL AUTOCORRELATION APPROACH

This paper evaluates experimentally the performance of a novel axial v elocity estimator, originally introduced in [4] and referred to as the 2D autocorrelator, and its Doppler power estimation counterpart, the 2D zero-lag autocorrelator, in the context of ultrasound color Row map ping, The evaluation also encompasses the well-established 1D autocorr elation technique for velocity estimation and its corresponding power estimator (1D zero-lag autocorrelator), to allow performance compariso ns under identical conditions. Clutter-suppressed in vitro data sets f rom a steady-flow system are used to document the effect of the range gate and ensemble length, noise level and angle of insonation on the p recision of the velocity estimates, The same data sets are used to exa mine issues related to the estimation of the Doppler signal's power, T he first-order statistics of power estimates from regions correspondin g to flow and noise are determined experimentally and the ability of p ower-based thresholding to separate flow signals from noise is charact erized by means of ROC analysis, In summary, the results of the in vit ro evaluation show that the proposed 2D-autocorrelatlon form of proces sing is consistently better than the corresponding 1D-autocorrelation techniques, in terms of both velocity and power estimation, Therefore, given their relatively modest implementation requirements, the 2D aut ocorrelation algorithms for velocity and power estimation appear to re present a superior, yet realistic, alternative to conventional Doppler processing for color flow mapping.