3D Myocardial Elastography <italic>In Vivo</italic>

Abstract

Strain evaluation is of major interest in clinical cardiology as it can quantify the cardiac function. Myocardial elastography, a radio-frequency (RF)-based cross-correlation method, has been developed to evaluate the local strain distribution in the heart in vivo. However, inhomogeneities such as RF ablation lesions or infarction require a three-dimensional approach to be measured accurately. In addition, acquisitions at high volume rate are essential to evaluate the cardiac strain in three dimensions. Conventional focused transmit schemes using 2D matrix arrays, trade off sufficient volume rate for beam density or sector size to image rapid moving structure such as the heart, which lowers accuracy and precision in the strain estimation. In this study, we developed 3D myocardial elastography at high volume rates using diverging wave transmits to evaluate the local axial strain distribution in three dimensions in three open-chest canines before and after radio-frequency ablation. Acquisitions were performed with a 2.5 MHz 2D matrix array fully programmable used to emit 2000 diverging waves at 2000 volumes/s. Incremental displacements and strains enabled the visualization of rapid events during the QRS complex along with the different phases of the cardiac cycle in entire volumes. Cumulative displacement and strain volumes depict high contrast between non-ablated and ablated myocardium at the lesion location, mapping the tissue coagulation. 3D myocardial strain elastography could thus become an important technique to measure the regional strain distribution in three dimensions in humans.

Author Correction: Impact of imaging cross-section on visualization of thyroid microvessels using ultrasound: Pilot study

“…An important question is: What are the disastrous consequences of imaging thyroid microvasculature with increased out-of-plane motion? Three obvious consequences are that this could (i) substantially hamper any efforts in motion tracking and correction, in the absence of 3D ultrasound imaging that is currently at a very nascent stage of development and implementation 7 ; (ii) would require advanced performance metrics for real-time assessment of the coherence of the acquired data to identify frames subjected to out-of-plane motion, which must be discarded prior to slow-time PD integration 6 , 8 . Further, discarding frames from the Doppler ensemble will inadvertently hamper the quality of the PD image, especially since flow signal in ultrasound images are only marginally higher than the noise floor 1 ; (iii) would complicate implementation of real-time imaging—a crucial feature of 2D ultrasound—for comprehensive assessment of the thyroid microvasculature in the entire nodule 9 .…”

Reproducibility and Angle Independence of Electromechanical Wave Imaging for the Measurement of Electromechanical Activation during Sinus Rhythm in Healthy Humans

“…Three-dimensional echocardiography in a single cardiac cycle would require additional hardware and processing methods, but has been shown to be feasible using plane waves (Papadacci et al 2017a) or diverging waves for a wider field of view. Our group recently showed initial feasibility of 3D strain imaging in the heart at very high volume rates (Papadacci et al 2017b). Further optimization will be conducted to perform 3D Electromechanical Wave Imaging.…”

“…Initial results on premature ventricular contractions (PVCs) and Wolff Parkinson White (WPW) syndrome patients have been reported (Costet 2016a) for potential applications in radiofrequency (RF) ablation treatment planning (Papadacci et al 2017b, Bunting et al 2016). Accordingly, it is essential that the arrhythmic focus or re-entry pathway locations identified with EWI remain consistent, no matter the position and orientation of the ultrasound probe.…”

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

“…The former was already demonstrated capable to reduce MLT/MLA artifacts [50] by exploiting the coherence of received echoes in the beamforming; however, it involves additional computational load that might impact on the maximum achievable frame rates in real-time. The transmission of several diverging waves with compounding in reception is gaining increasing interest for HFR imaging and was shown effective for several cardiac applications [26], [51], [27], [53], [29], [54]; even if it generates strong artifacts, due to the transmission of defocused beams, it is hard to predict their (either positive or negative) impact on TDI artifacts. Finally, second harmonic imaging inherently reduces artifacts due to grating lobes and was also shown, in a simulation study, to be effective on MLT imaging artifacts [52].…”