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Cardiac function has traditionally been studied using pressure-volume (PV) loop analysis. PV loops can be used to derive functional indices such as end-systolic pressure volume relationship (ESPVR)—a measure of myocardial contractility, end-diastolic pressure volume relationship (EDPVR) — a measure of myocardial compliance and relaxation time constant (τ) — a measure of left ventricular relaxation...
Myocardial strain imaging has been shown to add significant prognostic and diagnostic value to echocardiography. While the reliability of ultrasound-based strain measurement techniques has improved considerably in terms of regional consistency and inter-reader, inter-vendor agreement; most state-of-the-art strain imaging packages constrain their analyses to individual cardiac cycles. This limitation...
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...
Although 3D ultrasound plays an increasingly important role, 2D echocardiography remains the main clinical imaging modality for cardiac function assessment in daily practice. This requires precise delineation of the myocardium at end diastole (ED) and systole (ES). Because of intrinsic high variability in image quality, manual interactions are still needed. In this study, we investigate a machine...
Microembolization during PCI for acute myocardial infarction can cause microvascular obstruction (MVO). MVO severely limits the success of reperfusion therapies and is linked to worse prognosis, including death. A recent clinical trial showed that adjunct short pulse MB+US therapy prior to and following PCI in first STEMI patients, improved angiographic recanalization prior to PCI and ejection fraction...
Time delay estimation using cross correlation between successive RF lines is an established method to estimate tissue velocity. We have applied this method on our system using 10 MHz transducers sutured to the epicardium to measure the myocardial contraction pattern at high spatial and temporal resolution. In this setup, the myocardial tissue velocity will generally increase with the depth, as the...
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...
Myocardial deformation imaging at a high frame rate (HFR) has the potential to gain new insights in cardiac mechanics by resolving short-lived mechanical events during the cardiac cycle. In order to achieve such high frame rate, our lab recently proposed to combine multi-line transmit with ‘anatomical imaging’ i.e. imaging only the anatomically relevant spatial domain (e.g. the myocardium). Although...
Tissue Doppler Imaging (TDI) is an excellent tool for early detection of myocardial dysfunction, as well as for prognosis and follow-up of the myocardial function after surgical treatment. However, since it exploits the same principles of color flow imaging, TDI requires to balance frame rate with field of view. A novel TDI technique based on multiline transmission (MLT), i.e. the simultaneous transmission...
Tissue Doppler Imaging (TDI) is an excellent tool for early detection of myocardial dysfunction, as well as for prognosis and follow-up of myocardial function after surgical treatment. However, since it exploits the same principles of color flow imaging, TDI requires to balance frame rate with field of view. A novel TDI technique, based on multi-line transmission and multi-line acquisition, was shown...
Abnormal biomechanical properties of the myocardium, such as increased passive stiffness, prevent the heart of patients with diastolic heart failure to completely relax during diastole. Therefore, non-invasively measuring the stiffness is of importance. In this study, we used shear wave propagation velocities as a measure of stiffness of a thin plate phantom. We tested the applicability of a spatio-temporal...
ARFI displacements have been shown to share an inverse relationship with shear wave speed — based estimates of tissue elasticity. Both ARFI and shear wave elasticity imaging (SWEI) have been used to track the stiffening and softening of myocardium through the cardiac cycle in open-chest, intracardiac, and Langendorff preparations. In transthoracic imaging, induced shear waves have been observed during...
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...
Strain imaging is gaining traction as a means to assess cardiac function by tracking the cyclic deformation of the myocardium. Compared to traditional measures such as ejection fraction, global myocardial strain has been shown to be an earlier and more sensitive measure of overall ventricular function. Similarly, regional myocardial strain has been shown to be useful for identifying ischemia and myocardial...
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...
Myocardial elastance, derived from pressure-volume (PV) loops in the left ventricle (LV), can be used to assess LV function and myocardial performance. This method requires an invasive intracardiac pressure-volume catheter to be inserted in the LV, limiting the method's utility in clinical screening and monitoring. Strain echocardiography and cardiac acoustic radiation force impulse (ARFI) imaging...
Investigating myocardial dynamics through the assessment of mechanical properties of heart is a challenging problem in a murine model as the heart rate is high. The objective of this study was to compare displacements estimated using radiofrequency (RF) signals with Cardiac Elastography (CE) and Speckle Tracking Echocardiography (STE) for quantifying myocardial dynamics.
Left intraventricular blood flow follows a range of patterns that are mostly overlooked when using conventional ultrasound Doppler techniques. Vortices, in particular, as a blood redirection mechanism, could provide important information on a patient's cardiovascular health. They are not usually visualized, however, due to the need for 2D velocity vector visualization, and their transient nature,...
High speed ultrasound imaging is a new imaging method particularly applicable to cardiology. At Duke we have developed a real time high speed imaging system capable of producing up to 2500 images per second while maintaining the live imaging feature so essential in clinical scanning. For high speed 2D the Duke system, T5, uses 96 transmitters and 96 receivers at 32:1 parallel processing in conjunction...
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