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Noninvasive imaging of physiologic currents in the body is limited by poor spatial resolution due to the ambiguous conductivity distribution between the current sources and recording electrodes. Acoustoelectric imaging (AEI), based on the interaction between pressure and resistivity, provides higher spatial resolution. Although we have demonstrated AEI of the cardiac activation wave in the live rabbit...
Acoustic Angiography enables high resolution and high SNR imaging of microbubble contrast agents. The technique relies on pulsing and receiving at two widely separated acoustic bandwidths to reject signal from the tissue. To date this technique has been used to evaluate microvasculature within tumors and kidneys, but has not been used to visualize in vivo blood flow within heart, or liver. These targets...
Fast cardiac imaging requires a reduction of the number of transmit events. This is typically achieved through multi-line-transmission (MLT) and/or multi-line-acquisition (MLA) techniques. However, restricting the field-of-view (FOV) to the anatomically relevant domain, e.g. the myocardium, can increase frame rate (FR) further. Using computer simulations, we previously proposed an anatomical scan...
Cardiac pathologies are often characterized by important changes of myocardial properties such as the myocardial stiffness, re-organization of muscle fiber structure, modification of the microcirculation flow, all of which remain challenging to assess quantitatively and non-invasively in vivo. Over the last decade, the advent of software-based systems has enabled the implementation of ultrafast ultrasound...
Assessing the response of heart failure (HF) patients to Cardiac Resynchronization Therapy (CRT) currently relies on the ECG and left ventricular (LV) ejection fraction. Electromechanical Wave Imaging (EWI) is a high frame-rate (2000 Hz) ultrasound-based technique capable of non-invasively mapping the electromechanical activation in all four cardiac chambers in vivo. In this study, we aim to show...
Direct access to the electrical activation in the heart is crucial for understanding and diagnosing cardiac activation diseases such as arrhythmias. We have recently presented a fully integrated Ultrafast Acoustoelectric Imaging (UAI) system based on the acoustoelectric effect1 i.e., the modulation of the electrical impedance of a tissue by an ultrasound wave, which uses plane wave emissions to provide...
Dysfunctions on the coronary circulation can lead to adverse and severe clinical outcomes, e.g., ischemic heart failure (IHF) or coronary artery disease (CAD). The evaluation of coronary vasculature is consequently of extreme importance to the diagnosis of these conditions. However, intramyocardial coronary vasculature cannot yet be imaged in-vivo in humans with current angiography techniques or transthoracic...
Increased myocardial stiffness is characteristic of many diseases, leads to a loss of diastolic function, and is a cause of diastolic heart failure (DHF). Methods to estimate myocardial stiffness include Shear Wave Elastography (SWE). Currently, ultrasound-based cardiac SWE includes acoustic radiation force (ARF)-based methods; however, the in vivo generation and detection of the shear waves in myocardium...
Arrhythmias can be treated by ablating the heart tissue in the regions of abnormal conduction, e.g. activating too early or with a different speed. The key of the treatment then lies in the location of these areas. In current clinical practice, 3-D electroanatomic maps can be created during the procedure by probing the heart with a specific catheter. However, it is a time-consuming and invasive procedure...
Plane-wave imaging has been demonstrated in humans for cardiovascular (CV) studies, but its use in mouse embryo models has received minimal attention even though the mouse is the most common experimental organism to study gene function and human disease, including CV disease (CVD). While high-frequency ultrasound Doppler modes have been used to study mouse embryo models, traditional linear-array imaging...
Atrial fibrillation and ventricular tachycardia are currently treated with catheter ablation using radiofrequency or cryoenergy. These endocardiac approaches are invasive and not fully satisfactory as the treatments are often incomplete and can be associated with side effects. HIFU were proposed as an alternative strategy, by using the excellent acoustic window between heart and esophagus. The present...
Patients with chronic heart failure have reduced cardiac output and capacity for exercise-induced capillary vasodilation. Clinicians use left ventricular assist device (LVAD) therapy to improve physical function, but LVAD devices are designed to provide continuous blood flow and cannot increase blood flow in response to demand (i.e., exercise). Hence, this study investigated whether skeletal muscle...
3D Ultrasound Backscatter Tensor Imaging (3D-BTI) is a novel approach based on 3D Ultrafast Ultrasound Imaging to map fiber orientation in tissues such as the human heart in vivo [1]. Fiber orientations are obtained in entire volumes at high frame rate by computing and analyzing a voxel-wise coherence function relying on the synthetic focusing of multiple tilted plane waves. However, in rapidly moving...
Cardiac conduction abnormalities and arrhythmias are linked to stroke, heart failure, and sudden cardiac death and continue to be a major cause of death and disability worldwide. However, the evaluation of cardiac conduction remains challenging in the clinical setting. Electromechanical Wave Imaging (EWI) [1] was recently developed to map the transient displacements [1] and deformations [2] of the...
Physiologically important pressures in the heart and aorta are currently assessed with invasive pressure catheters. The subharmonic signal from ultrasound contrast agents, however, may be exploited to estimate pressures non-invasively. The objective of this work was (i) to develop a static phantom from commercially-available components for easy replication across different laboratories, and (ii) to...
Fast mechanical waves following e.g. electromechanical activation and aortic valve closure (AVC) have been imaged using 2D diverging waves (DW). However, their full characterization requires multiple 2D recordings in subsequent heartbeats. Given the heart cycle variability and short-lived nature of these waves, temporal alignment is challenging. Moreover, clinical matrix arrays hinder the straightforward...
Electromechanical wave imaging (EWI) is an ultrasound-based methodology that can map the electromechanical activation of the heart at high temporal resolution. Previous reports have shown strong correlation between EWI-based and electrical activation times. However, EWI has been performed only with 2D echocardiography, which cannot map the full cardiac volume in a single heartbeat. Our objective in...
Chronic and advanced heart failure patients experience reduced capacity for exercise, likely due to reduced cardiac output and exercise-induced capillary vasodilation. To address these symptoms, clinicians implant a left ventricular assist device (LVAD) to improve physical function for this patient population. However, most LVADs, including the HeartMateII investigated in this study, are designed...
Increased myocardial stiffness is characteristic of many diseases, leads to a loss of diastolic function, and is a cause of diastolic heart failure (DHF). Methods to estimate myocardial stiffness include Shear Wave Elastography (SWE). Currently, ultrasound-based cardiac SWE includes acoustic radiation force (ARF)-based methods; however, the in vivo generation and detection of shear waves in myocardium...
ARFI displacements have been shown to share an inverse relationship with shear wave speed — based estimates of tissue elasticity. In transthoracic imaging, induced shear waves have been observed during diastole, but only ARFI displacements have been accurately measured through both diastole and systole. We propose here a method for using diastolic shear wave speeds to calibrate ARFI displacement magnitudes,...
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