Gated Volumetric Ultrasound Imaging of Cardiac and Vascular Dynamics

Conventional ultrasound measurements are commonly based on geometric assumptions from 2D images, often yielding inaccurate results with large variability. In this study, we developed a respiratory- and cardiac-gated 3D... [ view full abstract ]

Conventional ultrasound measurements are commonly based on geometric assumptions from 2D images, often yielding inaccurate results with large variability. In this study, we developed a respiratory- and cardiac-gated 3D echocardiography technique to reconstruct ultrasound volumes. We imaged 1) the left ventricles of healthy wild-type C57Bl/6 mice (n=5) and 2) the abdominal aortas of hyperlipidemic mice with angiotensin II-induced aneurysms (n=5) using a position-controlled 40MHz transducer. ECG-gated cine loops at 1000 frames-per-second were acquired at sequential positions and temporally concatenated, generating 4D datasets. Nonlinear image registration was then utilized to calculate deformation fields and project segmented masks across the cardiac cycle (Figure 1) and from aneurysmal vessels (Figure 2). Volume renderings of left-ventricular masks yielded ejection fractions of 68±6% and stroke volumes of 28±7μL. In the abdominal aorta, Green-Lagrange circumferential cyclic strain decreased significantly between healthy and aneurysmal regions (9.3±5.3% vs. 1.1±0.2%; p<0.01). The presented technique demonstrates an innovative approach to studying cardiac and vascular dynamics and allows for visualization of complex geometries. Future work can use this technique to study animal disease models of myocardial infarction, aortic stenosis, or other dynamic imaging applications to learn more about hemodynamics and biomechanics in small animals.