THE EFFECT OF ECHO SUPPRESSION ON THE MEAN VELOCITY ESTIMATION RANGE OF THE RF CROSS-CORRELATION MODEL ESTIMATOR

Ultrasound systems are widely used to visualize in real-time internal structures and blood flow velocity distributions. The latter are estim ated from the received ultrasound radio frequency (RIF) signals using a mean frequency estimator, capable of estimating the temporal and spa tial mean frequency within a given depth and time window (estimation w indow), Since ultrasound RF-signals are composed of three major signal components (reflections, scattering and noise) it is necessary to sup press the power of the reflections or reverberations (stationary echo removal) to estimate the temporal mean frequency of the signal compone nt induced by scattering originating from red blood cells, However, th e stationary echo removal filter in front of the mean frequency estima tor will restrict the temporal mean frequency estimation range because the power of the signal component induced by the slowly moving blood is suppressed as well. This article describes a stationary echo remova l filter, acting in the RF-domain and adaptive to the temporal mean fr equency of the signal component induced by stationary or slowly moving reflections and reverberations, Furthermore, a comparison in performa nce of this adaptive stationary echo removal filter and several static stationary echo removal filters is presented. For direct comparison o f these filter algorithms as far as the effect on the temporal mean fr equency estimation range is concerned, the same signal conditions in c ombination with the same RF-domain mean frequency estimator were used in this comparison. It could be demonstrated that the adaptive echo re moval filter, in combination with the RF-domain mean frequency estimat or used, exhibits the best performance.