Comparison of multiple beam sequences in arterial ARFI imaging, ex vivo

Acoustic Radiation Force Impulse (ARFI) has been demonstrated for differentiating mechanical properties in a variety of tissues. To fully maximize the potential of ARFI imaging in the context of material characterization of atherosclerosis it is important to understand the benefits and drawbacks of various radiation force excitation and tracking methods. We investigated the impact of five excitation methods and two tracking methods of radiation force beam sequences in a pig model of hypercholesterolemic atherosclerosis. The pigs were either familial hypercholesterolemic (FH) or dietary hypercholesterolemic (DH). First, we compared two methods of A-line receiving: single receive (SRX) and parallel receive (ParRX) in a FH female pig. Second, ARFI excitations with varying F/#'s of F/1, F/1.5, F/2, and F/3, were examined in another FH female. Lastly, to compare the utility of multiple ARFI excitations, both single excitation pulse ARFI (SP) and double excitation pulse ARFI (DP) were compared in a DH female. Comparing A-line receiving methods, SP-ParRX was observed to have lower spatial sensitivity to local variation of mechanical property than SP-SRX. Large excitation pulse F/#'s were observed to yield more variability in measured ARFI parameters in the location of a large calcification and better differentiation of local variations in material content. DP ARFI provided useful insights that were supplemental to those provided by SP ARFI alone.