Staggered Multiple-PRF Ultrafast Color Doppler

Abstract

Color Doppler imaging is an established pulsed ultrasound technique to visualize blood flow non-invasively. High-frame-rate (ultrafast) color Doppler, by emissions of plane or circular wavefronts, allows severalfold increase in frame rates. Conventional and ultrafast color Doppler are both limited by the range-velocity dilemma, which may result in velocity folding (aliasing) for large depths and/or large velocities. We investigated multiple pulse-repetition-frequency (PRF) emissions arranged in a series of staggered intervals to remove aliasing in ultrafast color Doppler. Staggered PRF is an emission process where time delays between successive pulse transmissions change in an alternating way. We tested staggered dual- and triple-PRF ultrafast color Doppler, 1) in vitro in a spinning disc and a free jet flow, and 2) in vivo in a human left ventricle. The in vitro results showed that the Nyquist velocity could be extended to up to 6 times the conventional limit. We found coefficients of determination r(2) ≥ 0.98 between the de-aliased and ground-truth velocities. Consistent de-aliased Doppler images were also obtained in the human left heart. Our results demonstrate that staggered multiple-PRF ultrafast color Doppler is efficient for high-velocity high-frame-rate blood flow imaging. This is particularly relevant for new developments in ultrasound imaging relying on accurate velocity measurements.

Extension of Fourier-Based Techniques for Ultrafast Imaging in Ultrasound With Diverging Waves

“…number of firing elements, steering angles or number of PW). Although ultrafast imaging based on coherent compounding using SPW is a recent technique, it has been already applied in many applications, such as transient elastography, pulse wave velocity imaging, flow imaging, shear wave imaging, ultrafast Doppler imaging and electromechanical wave imaging [10], [12]- [23].…”

Ultrasound Vector Flow Imaging: I: Sequential Systems

“…Another issue is the presence of aliasing in color Doppler. Range cross-correlation techniques [121], [96] or staggered transmit sequences [122] can provide solutions to this problem.…”

“…As mentioned above, these techniques are limited by their relatively low frame rates. Ongoing studies on transthoracic high-frame-rate echocardiography could change the situation in a near future [167], [122], [168]. This is the author's version of an article that has been published in this journal.…”

Ultrasonic Vascular Vector Flow Mapping for 2-D Flow Estimation

“…Understanding the 2-D flow patterns in the vasculature may be of great clinical importance, and an emerging interest is exploring novel ways of using ultrasound to quantitatively assess complex hemodynamic patterns under different pathologic conditions such as stenosis and plaque ulceration (Jensen et al 2016;Posada et al 2016). Hemodynamic parameters derived from a flow pattern enable highly atherosclerosis-susceptible endothelium to be distinguished from atherosclerosis-resistant endothelium (Gimbrone and Garcia-Cardena 2013).…”

“…Several echocardiographic and vascular 2-D flow measurement methods have recently been reported (Jensen et al 2016;Kim et al 2004;Posada et al 2016;Sengupta et al 2012). We have previously reported a vector flow mapping (VFM) method (Itatani et al 2013) that utilizes color Doppler velocities and tissue-tracking information of the cardiac wall to estimate the velocities of lateral directional flow by using the mass conservation equation assuming a planar flow (Garcia et al 2010;Ohtsuki and Tanaka 2006).…”