Ultraharmonic intravascular ultrasound imaging with commercial 40 MHz catheter: A feasibility study

Abstract

The abnormal growth of the vasa vasorum is characteristic of life-threatening atherosclerotic plaques. Intravascular ultraharmonic imaging is an emerging technique that could visualize the vasa vasorum and help clinicians identify life-threatening plaques. Implementing this technique on commercial intravascular ultrasound (IVUS) systems could to accelerate its clinical translation. Our previous work has demonstrated ultraharmonic IVUS imaging with a modified clinical system that was equipped with a commercial 15 MHz peripheral imaging catheter. In the present study, we investigated the feasibility of ultraharmonic imaging with a commercially available 40 MHz coronary imaging catheter. We imaged a flow phantom that had contrast agent microbubbles (Targestar-P-HF, Targeson Inc., CA) perfused in side channels parallel to its main lumen. The transducer was excited at 30 MHz using 10% bandwidth chirp-coded pulses. The ultraharmonic response at 45 MHz was isolated and preferentially visualized using pulse inversion and digital filtering. Side channels with 900 μm and 500 μm diameter were detected with contrast-to-tissue ratios approaching 10 dB for clinically relevant microbubble concentrations. The results of this study indicate that ultraharmonic imaging is feasible with commercially available coronary IVUS catheters, which may facilitate its widespread application in preclinical research and clinical imaging.