A 20-40 MHz ultrasound transducer for intravascular harmonic imaging

Abstract

Recent studies have suggested the feasibility of tissue harmonic imaging (THI) with intravascular ultrasound (IVUS). This paper describes the design, fabrication and characterization of a piezo-electric transducer optimized for tissue harmonic IVUS. Ideally, such a transducer should efficiently transmit a short acoustic pulse at the fundamental transmission frequency and should be sensitive to its second harmonic echo, for which we have chosen 20 MHz and 40 MHz, respectively. The intravascular application limits the transducer dimensions to 0.75 mm by 1 mm. The transducer comprises of a single piezoelectric layer design with additional passive layers for tuning and efficiency improvement, and the Krimholtz-Leedom-Matthaei (KLM) model was used to find iteratively optimal material properties of the different layers. Based on the optimized design a prototype of the transducer was built. The transducer was characterized by water-tank hydrophone measurements and pulse-echo measurements. These measurements showed the transducer to have two frequency bands around 20 MHz and 40 MHz with -6dB fractional bandwidths of 30 % and 25 %, and round-trip insertion losses of -19 dB and -34 dB, respectively.

Nonlinear intravascular ultrasound contrast imaging

“…Such transducers may enable improvements in axial resolution and improve SNR, and have been previously investigated at lower frequencies (e.g., Bouakaz et al 2003;Forsberg et al 2004). A prototype IVUS transducer element has been developed for this purpose (Vos et al 2005), and its application to nonlinear contrast studies is currently being investigated. Alternatively, it may also be possible to employ detection strategies that detect nonlinear bubble behavior within the transmit frequency band (e.g., Brock-Fisher et al 1996;Shen and Li 2003).…”

High‐Frequency Surface Dynamics at an Electroactive Polymer Producing Underwater Soundwaves

“…The results indicate that the coatings indeed have the capability to transmit and detect sound waves underwater. Still, the performance is about 10 times lower than typical underwater transducers, [ 30–33 ] although there are some practical measures to improve this further. For instance, the receive transfer function could be increased by reducing the gap height and coating thickness, which will increase the electrostatic effect.…”

Intravascular ultrasound tissue harmonic imaging in vivo

“…We recently reported the development of an IVUS transducer element designed for 20-40 MHz harmonic imaging [24]. The element combines improved transmit efficiency at 20 MHz and a high sensitivity at 40 MHz, and it is anticipated to result in an increased SNR in harmonic acquisitions.…”