Atherosclerosis is associated with the formation of microvessels in the arterial wall, referred to as vasa vasorum (VV). VV imaging may constitute a new intravascular ultrasound (IVUS) metric of coronary artery plaque vulnerability. The potential of nonlinear contrast IVUS to detect VV in vivo was demonstrated using a prototype transducer with dual-peak frequency response. In this study, we report the feasibility of pulse-inversion ultraharmonic IVUS contrast imaging and6 chirp reversal contrast IVUS imaging. Their performance is compared for VV detection. Both sequences operate with limited transducer bandwidths (<60%), and are therefore implementable on clinical IVUS catheters.@en

We demonstrate the feasibility of intravascular ultrasound (IVUS) chirp imaging as well as chirp reversal ultrasound contrast imaging at intravascular ultrasound frequency. Chirp excitations were emitted with a 34 MHz single crystal intravascular transducer and compared to conventional Gaussian-shaped pulses of equal acoustic pressure. The signal to noise ratio of the chirp images was increased by up to 9 dB relative to the conventional images. Imaging of contrast microbubbles was implemented by chirp reversal, achieving a contrast to tissue ratio of 12 dB. The method shows potential for intravascular imaging of structures in and beyond coronary atherosclerotic plaques including vasa vasorum.@en