80-MHz intravascular ultrasound transducer using PMN-PT free-standing film

Abstract

[Pb(Mg1/3Nb2/3)O3]0.63[PbTiO3]0.37 (PMN-PT) free standing film of comparable piezoelectric property to bulk PMN-PT with a thickness of 33 μm has been fabricated using a modified precursor coating approach. At 1 KHz, the dielectric constant and loss were 4,160 and 0.0291, respectively. The remnant polarization and coercive field were 28 μC/cm2 and 18.43 kV/cm. The electromechanical coupling coefficient kt was measured to be 0.55, which was close to that of bulk PMN-PT single crystal material. A high frequency (80 MHz) miniature ultrasonic transducer with high sensitivity was fabricated from this film. In vitro imaging of a rabbit aorta was performed to demonstrate the application of this material to intravascular ultrasound imaging at 80 MHz. Compared to a 35 MHz ultrasonic image, the 80 MHz image showed superior resolution and contrast.

Multi-frequency intravascular ultrasound (IVUS) imaging

“…Electromechanical coupling coefficient ( k t ), piezoelectric coefficient ( d 33 ) and dielectric permittivity ( ${\epsilon }_{33}^{\mathrm{s}}/{\epsilon }_0$), listed in Table I, are the major parameters that determine the performance of a transducer [23]. Because the transducer aperture size is already determined in this study, the effects caused by dielectric permittivity should be carefully taken into account during the material selection because the dielectric permittivity, together with the surface area of piezoelectric material, determines the electrical impedance of a transducer [22]. An electrical impedance of 50 Ω properly matched to the electronics will result in an optimized sensitivity in both transmitting and receiving.…”

“…Given the fact that OCT is the optical analog of ultrasound, a question is then raised: can ultra-high frequency ultrasonic imaging be considered as an alternative and cost-effective solution to replace OCT? Ultra-high frequency IVUS at 80 MHz has been previously investigated and proved to be able to improve artery characterization with much higher axial resolution [22]. Even though there is a foreseeable drawback that higher frequency ultrasound will have stronger attenuation in the blood and vascular tissue, such transducers at 80 MHz center frequency can still provide an imaging depth of 2 mm, which is comparable to the penetration depth of OCT.…”

An IVUS transducer for microbubble therapies

“…Both ceramics demonstrated superior performance in the desired frequency range of 1 to 2 MHz, although PZT5H has a higher bandwidth and more distinct resonance. Ultimately, PZT5H was selected instead of PMN-PT because of its higher Curie temperature and easier machinability [49], [50]. …”

Intravascular Ultrasound Imaging With Virtual Source Synthetic Aperture Focusing and Coherence Factor Weighting

“…1000 scan lines were acquired with a 3.6 μm step size to form the wire phantom image. During rotational scanning, the transducer tip remained stationary within the water-filled lumen of the imaged sample (wire phantom, agar phantom, and human artery) and cross-sectional images were achieved by rotating the sample using an integrated servo motor (Moog Animatics, Milpitas, CA, USA) [40]. 1000 scan lines were acquired with a 0.36° angular step size corresponding to around λ /12 step size at the transducer surface to ensure enough beam overlap between adjacent scan lines.…”