Real-Time High-Frame-Rate Cardiac B-Mode and Tissue Doppler Imaging Based on Multiline Transmission and Multiline Acquisition

Abstract

Cardiovascular diseases, the leading cause of death in the world, are often associated with the dysfunction of the left ventricle. Even if, in clinical practice, the myocardial function is often assessed through visual wall motion scoring on B-mode images, quantitative techniques have been introduced, e.g. ultrasound tissue Doppler imaging (TDI). However, this technique suffers from the limited frame rate of currently available imaging techniques that needs to be balanced with the field of view. High frame rate (HFR) cardiac imaging has been recently tested off-line by simultaneously transmitting multiple focused beams into different directions and acquiring raw channel data into a PC. Several image lines were then reconstructed from the echoes of each transmission event. The same approach has been used to increase the TDI frame rate without restricting the field of view. This paper demonstrates the real-time feasibility of multiline transmission and acquisition methods for both HFR cardiac B-Mode and tissue Doppler imaging. These approaches have been implemented on the ULA-OP 256 research scanner, by taking care that the related resources were optimally exploited for these new applications. The obtainable performance in terms of image quality and frame rate has also been investigated. Experiments performed with a 128-element phased array probe show, for the first time, that real-time B-mode imaging is feasible at up to 1150 Hz without significant reduction in image quality or field-of-view. The implementation of a real-time TDI algorithm allowed obtaining TDI images with a frame rate of 288 Hz for a 90°-wide field-of view. Finally, in-vivo examples demonstrate the feasibility and the suitability of the method in clinical studies.

High-Frame-Rate Tri-Plane Echocardiography With Spiral Arrays: From Simulation to Real-Time Implementation

“…Instead, it would be preferable implementing smarter imaging modes that could achieve, in real-time, the same FRMax but with an improved quality of images. For example, since the current architecture of the ULA-OP 256 system allows reconstructing up to 32 lines per transmission event, when being limited by PRFMax [43] in real-time cardiac applications, SPT is too much demanding (100 lines per transmission event) and a different transmission scheme should be implemented. An option could be the transmission of diverging waves having narrower aperture angles to scan each plane in several (e.g.…”

“…In general, continuous real-time HFR imaging is beneficial when subsequent processing is applied to produce additional information in real-time, e.g. tissue-motion [43] or color flow imaging [69]. For example, through the implementation of a speckle tracking technique, the frame rate achieved in this work with SPT and MPT (250 Hz) might enable real-time functional analysis of all left ventricular segments of the heart.…”

“…where ⌊•⌉ is the round to the closest integer operator and % is the modulus operator. Assuming a linear system, in order to simultaneously transmit nMLT beams into the ( ) directions, the excitation waveform for a given element is given by the sum of the pulses, each properly delayed, that would be used on that element to generate conventional SLT beams along the ( ) directions [43]. In tri-plane MLT imaging the theoretical final frame rate results:…”

Coded Excitation for Crosstalk Suppression in Multi-line Transmit Beamforming: Simulation Study and Experimental Validation

“…Intrinsically, crosstalk artifacts are the results of the interference between MLT beams in different directions. It has been demonstrated that such crosstalk artifacts can be largely suppressed by using a Tukey (α = 0.5)-Tukey (α = 0.5) (TT) transmit and receive apodization scheme; so that the resulting MLT images look competitive to the conventional single line transmit beamforming (SLT) ( Figure 2b) [8,9,11]. Nonetheless, despite these promising results, residual crosstalk artifacts can sometimes be detected [9].…”

Comparison Between Multiline Transmission and Diverging Wave Imaging: Assessment of Image Quality and Motion Estimation Accuracy

“…Since MLT is prone to cross-talks, many studies focused on reducing the image artifacts [16], [17], [14]. Although tissue Doppler imaging (TDI) has been applied to MLT images [18], [19] this beamforming method has received little attention in motion estimation.…”