Analysis of rapid multi-focal-zone ARFI imaging.

Acoustic radiation force impulse (ARFI) imaging has shown promise for visualizing structure and pathology within multiple organs; however, because the contrast depends on the push beam excitation width, image quality suffers outside of the region of excitation. Multi-focal-zone ARFI imaging has previously been used to extend the region of excitation (ROE), but the increased acquisition duration and acoustic exposure have limited its utility. Supersonic shear wave imaging has previously demonstrated that through technological improvements in ultrasound scanners and power supplies, it is possible to rapidly push at multiple locations before tracking displacements, facilitating extended depth of field shear wave sources. Similarly, ARFI imaging can utilize these same radiation force excitations to achieve tight pushing beams with a large depth of field. Finite element method simulations and experimental data are presented, demonstrating that single- and rapid multi-focal-zone ARFI have comparable image quality (less than 20% loss in contrast), but the multi-focal-zone approach has an extended axial region of excitation. Additionally, as compared with single-push sequences, the rapid multi-focalzone acquisitions improve the contrast-to-noise ratio by up to 40% in an example 4-mm-diameter lesion.