Color Doppler and spectral Doppler with high frame-rate imaging

Color Doppler imaging (CDI) produces qualitative blood flow information in a 2D region of interest (ROI) but has low temporal resolution, while spectral Doppler can provide quantitative information, but its measurements are limited along a single scanline. These are inherent limitations associated with the conventional focused pulse-echo method. The unfocused transmit method has the potential to overcome these limitations by providing quantitative data in a 2D ROI with high temporal resolution. However, it is known that the unfocused method has poor spatial resolution with low SNR and the generated images contain strong side-lobe artifacts. In this paper, we present the preliminary results from comparing the focused and unfocused methods on CDI and spectral Doppler. For this study, we used a Verasonics Ultrasound Engine, which can support both focused and unfocused transmit methods. Pre-beamformed RF data were acquired from the carotid arteries of healthy volunteers. The comparison shows that the unfocused method can generate CDIs and Doppler spectra similar to those generated by the focused method. Compared to the conventional focused method, high frame rates offered by the unfocused method could be advantageous in some clinical applications, e.g., pulse-wave velocity measurement.