80 MHz Intravascular Ultrasound (IVUS) transducer

[Pb(Mg_1/3Nb_2/3)O₃]0.63[PbTiO₃]0.37 (PMN-PT) free-standing film of comparable piezoelectric properties to bulk material with thickness of 30 μm has been fabricated using a modified precursor coating approach. At 1 kHz, the dielectric permittivity and loss were 4,364 and 0.033, respectively. The remnant polarization and coercive field were 28 μC/cm² and 18.43 kV/cm. The electromechanical coupling coefficient k_t was measured to be 0.55, which was close to that of bulk PMN-PT single crystal material. Based on this film, high frequency (82 MHz) miniature ultrasonic transducers were fabricated with 65% bandwidth and 23 dB insertion loss. Axial and lateral resolutions were determined to be as high as 35 μm and 176 μm. In vitro intravascular imaging on healthy rabbit aorta and human coronary artery was performed from the thin film transducers. In comparison with a 35 MHz IVUS transducer, the 80 MHz one showed superior resolution and contrast with satisfactory penetration depth. The imaging results suggest that PMN-PT free-standing thin film technology is a feasible and efficient way in fabricating very high frequency ultrasonic transducers.