High resolution color flow—application of coded excitation in color flow imaging

Abstract

Color flow imaging has suffered from the trade off between resolution and sensitivity ever since it was introduced. The requirement of blood flow sensitivity results in application of narrow bandwidth, long time duration pulses. The problem associated with this type of pulse is the severely degraded spatial resolution, which causes wall overwriting, blobby flow aesthetics, loss of detail flow hemodynamics, etc. Coded Excitation has been applied in B mode imaging to solve the similar tradeoff between SNR and resolution, but has not been so successful in color flow imaging. This is due to the fact that current color flow pulses are already at the regulatory limit and the focus of delivering more power for more sensitivity with coded excitation in color flow imaging. High resolution color flow imaging is an effort to introduce Chirp Coded-Excitation to achieve B-mode-like spatial resolution in color flow without sacrificing sensitivity. Wide bandwidth pulse with time bandwidth product greater than 1 is employed to bring in sensitivity/penetration and resolution. As a result, better spatial definitions, less wall overwriting, and detailed flow hemodynamics are achieved with improved flow sensitivity. Corresponding practical application issues are discussed in this paper.