High-frequency ultrasound imaging of left-ventricle vortex flow in a mouse model

Abstract

Vector flow (VF) ultrasound is available for human cardiac imaging to quantify advanced flow parameters such as vorticity, an important component of healthy cardiac function. Similar methods have yet to translate to murine models because of the need for fine temporal and spatial resolution. We evaluate the ability of a 30-MHz high-frequency probe to quantify vorticity in the murine left ventricle (LV) using a Verasonics Vantage 256. Acoustic beam properties were characterized with an 18-um wire. A 1-cm diameter rotation phantom and a flow channel were used to validate vector estimates. Transthoracic LV image data were acquired from wild-type mice. Flow parameters were obtained with custom software that implemented a multi-angle least-squares VF method. Data were processed to obtain VF estimates and local time histories of vorticity. Velocity and vorticity estimates had more bias as the axial velocity component decreased. Aliasing was observed and a basic dealiasing approach was implemented prior to final velocity estimates. Vorticity peaked during diastole at roughly 300 rad/s, consistent with past measurements at lower frequency. Results show VF can be implemented in murine models with HF probes, but that aliasing must be addressed to obtain reliable estimates. [Work supported by NIH EB032082.]