Anti-matching design for wave isolation in dual frequency transducer for intravascular super-harmonic imaging

Intravascular super-harmonic imaging of microvessels is expected to assist understanding of atherosclerotic cardiovascular disease. A dual frequency intravascular (IVUS) ultrasound transducer is a core component transmitting at low frequency and receiving high order harmonics. A significant challenge in developing high performance dual frequency IVUS transducers is the isolation of the high frequency ultrasound echoes from the low frequency element while keeping the low frequency transmission pressure. An anti-matching layer with low impedance and quarter wavelength thickness was designed based on wave propagation theory. In both KLM modeling and prototype validation, the anti-matching layer successfully suppressed the aliasing echo to less than-20 dB. Transmission pressure of the prototype transducer was still high enough for microbubble nonlinear responses. High resolution (<0.2 mm) and high CTR (>12 dB) image was generated from superharmonic imaging, which elucidated the capability of the transducer for intravascular microvessel detection.