Sparse Doppler Sensing Based on Nested Arrays

TL;DR

This paper introduces a nested array-based non-uniform transmission scheme for spectral Doppler ultrasound that reduces the number of pulses needed for accurate blood spectrum recovery, enabling higher frame rates and simultaneous imaging.

Contribution

It proposes a novel nested array approach for spectral Doppler, deriving the minimal pulses required and providing two efficient spectrum recovery methods.

Findings

Accurate blood velocity spectrograms achieved with fewer transmissions.

The methods outperform traditional approaches in simulation and in vivo tests.

Time savings enable higher frame rate imaging and dual-mode display.

Abstract

Spectral Doppler ultrasound imaging allows visualizing blood flow by estimating its velocity distribution over time. Duplex ultrasound is a modality in which an ultrasound system is used for displaying simultaneously both B-mode images and spectral Doppler data. In B-mode imaging short wide-band pulses are used to achieve sufficient spatial resolution in the images. In contrast, for Doppler imaging, narrow-band pulses are preferred in order to attain increased spectral resolution. Thus, the acquisition time must be shared between the two sequences. In this work, we propose a non-uniform slow-time transmission scheme for spectral Doppler, based on nested arrays, which reduces the number of pulses needed for accurate spectrum recovery. We derive the minimal number of Doppler emissions needed, using this approach, for perfect reconstruction of the blood spectrum in a noise-free environment. Next, we provide two spectrum recovery techniques which achieve this minimal number. The first method performs efficient recovery based on the fast Fourier transform. The second allows for continuous recovery of the Doppler frequencies, thus avoiding off-grid error leakage, at the expense of increased complexity. The performance of the techniques is evaluated using realistic Field II simulations as well as in vivo measurements, producing accurate spectrograms of the blood velocities using a significant reduced number of transmissions. The time gained, where no Doppler pulses are sent, can be used to enable the display of both blood velocities and high quality B-mode images at a high frame rate.