ON THE PERFORMANCE OF REGRESSION AND STEP-INITIALIZED IIR CLUTTER FILTERS FOR COLOR DOPPLER SYSTEMS IN DIAGNOSTIC MEDICAL ULTRASOUND

One of the major issues in color Doppler ultrasound is the suppression of clutter that arises from stationary or slowly moving tissue. If no t adequately suppressed, clutter can severely affect the ability of co lor Doppler systems to accurately estimate the Doppler mean frequency and power of blood, resulting in a potentially misleading depiction of flow. In this study, the performances of two classes of clutter suppr ession techniques-step-initialized infinite impulse response (IIR) and regression filters-were evaluated and compared by means of extensive simulations. The performance indicators used were the accuracy and pre cision of the mean frequency and the power estimates after clutter fil tering. In summary, the ability of both filter classes to suppress clu tter was found to vary considerably depending on factors such as the c lutter-to-flow-signal ratio and the ensemble length. In particular, th e performance of step-initialized IIR filters was shown to be noticeab ly inferior to that predicted by their steady-state response. Regressi on filters were found to offer significantly better performance than s tep-initialized IIR filters under heavy clutter conditions acid, given their steeper roll off, appear to be more effective clutter suppresso rs for power Doppler imaging. However, it should be noted that, as dem onstrated by the simulations, the performance of IIR filters is severe ly degraded by their transient response which, in turn, is determined by the initialization scheme used. Therefore, more elaborate schemes-w ith superior transient characteristics than step-initialization-could significantly improve the effectiveness of IIR filtering under heavy c lutter conditions.