Non-invasive carotid artery elastography using multi-element synthetic aperture and plane wave imaging: Phantom and in vivo evaluation

Vascular elastography can visualize the strain distribution in the carotid artery, which governs plaque rupture. In this study, we hypothesize that multi-element synthetic aperture (MSA) imaging, which produces divergent transmit beams can overcome the grating lobes issues associated with compounded plane wave (CPW) imaging, and produce more reliable strain elastograms. To corroborate this hypothesis, we conducted phantom and in vivo studies using both the techniques, and determined the most optimal imaging configuration for carotid elastography. The phantom studies were conducted using cryogel vessel phantoms. We validated the phantom study results in vivo, on healthy volunteers. These studies were performed using a commercially ultrasound scanner (Sonix RP, Ultrasonix Medical Corp., Richmond, BC, Canada), operating at a transmit frequency of 5 MHz. The phantom results demonstrated that the plaque was visible in elastograms from both techniques; however, MSA elastograms had fewer artifacts, with a 12 dB improvement in elastographic contrast to noise ratio relative to CPW imaging. Further, the results from the in vivo study agreed with the phantom results. These results suggest that MSA imaging can produce useful strain elastograms. Our future work will involve further development and more in vivo validation.