Comparison of narrowband and wideband color flow estimators in the presence of intervening tissue

In the presence of intervening tissue and frequency dependent scattering, and in the context of color flow mapping, the performance of color flow estimation strategies is compared. Wideband signal tranmission is desired in color flow mapping to improve two-dimensional spatial resolution. Since narrowband Doppler estimation strategies suffer from a bias that increases with signal bandwidth and the depth of the intervening tissue, wideband estimation strategies should be combined with wideband signal transmission. A wideband maximum likelihood strategy (WMLE), a cross correlation estimator, and the autocorrelator are considered. The cross correlation estimator and WMLE are unbiased in the presence of intervening tissue, whereas the traditional Doppler estimator and autocorrelator have a bias which increases with the depth of the intervening tissue. Both wideband estimation techniques provide similar local and global accuracy, with the position and height of subsidiary peaks actually changing in the presence of intervening tissue