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Echocardiography has the long development history beginning with amplitude imaging. Nowadays, two- and three- dimensional imaging are standard tools available in almost every echocardiography machine. Myocardial deformation imaging is gaining popularity out of research projects. The future will bring new and sophisticated tools for echocardiographic analysis such intracardiac flow imaging and an automated 3D volume calculation.

In vivo characterization of intracardiac blood velocity vector fields may provide new clinical information but is currently not available for bedside evaluation. In this paper, 4-D vector flow imaging for intracardiac flow assessment is demonstrated using a clinical ultrasound (US) system and a matrix array transducer, without the use of contrast agent. Two acquisition schemes were developed, one for full volumetric coverage of the left ventricle (LA) at 50 vps and a 3-D thick-slice setup with continuous frame acquisition (4000 vps), both utilizing ECG-gating. The 3-D vector velocity estimates were obtained using a novel method combining phase and envelope information. In vitro validation in a rotating tissue-mimicking phantom revealed velocity estimates in compliance with the ground truth, with a linear regression slope of 0.80, 0.77, and 1.03 for the ${x}$ , ${y}$ , and ${z}$ velocity components, and with standard deviations of 2.53, 3.19, and 0.95 cm/s, respectively. In vivo measurements in a healthy LV showed good agreement with PC-MRI. Quantitative analysis of energy loss (EL) and kinetic energy (KE) further showed similar trends, with peak KE at 1.5 and 2.4 mJ during systole and 3.6 and 3.1 mJ for diastole for US and PC-MRI. Similar for EL, 0.15– 0.2 and 0.7 mW was found during systole and 0.6 and 0.7 mW during diastole, for US and PC-MRI, respectively. Overall, a potential for US as a future modality for 4D cardiac vector flow imaging was demonstrated, which will be further evaluated in clinical studies. [ABSTRACT FROM AUTHOR]

Objective . Intraventricular vector flow mapping ( i VFM) is a velocimetric technique for retrieving two-dimensional velocity vector fields of blood flow in the left ventricular cavity. This method is based on conventional color Doppler imaging, which makes i VFM compatible with the clinical setting. We have generalized the i VFM for a three-dimensional reconstruction (3D- i VFM). Approach. 3D- i VFM is able to recover three-component velocity vector fields in a full intraventricular volume by using a clinical echocardiographic triplane mode. The 3D- i VFM problem was written in the spherical (radial, polar, azimuthal) coordinate system associated to the six half-planes produced by the triplane mode. As with the 2D version, the method is based on the mass conservation, and free-slip boundary conditions on the endocardial wall. These mechanical constraints were imposed in a least-squares minimization problem that was solved through the method of Lagrange multipliers. We validated 3D- i VFM in silico in a patient-specific CFD (computational fluid dynamics) model of cardiac flow and tested its clinical feasibility in vivo in patients and in one volunteer. Main results. The radial and polar components of the velocity were recovered satisfactorily in the CFD setup (correlation coefficients,r = 0.99 and 0.78). The azimuthal components were estimated with larger errors (r = 0.57) as only six samples were available in this direction. In both in silico and in vivo investigations, the dynamics of the intraventricular vortex that forms during diastole was deciphered by 3D- i VFM. In particular, the CFD results showed that the mean vorticity can be estimated accurately by 3D- i VFM. Significance . Our results tend to indicate that 3D- i VFM could provide full-volume echocardiographic information on left intraventricular hemodynamics from the clinical modality of triplane color Doppler., (© 2022 Institute of Physics and Engineering in Medicine.)