Dual-frequency transducer for nonlinear contrast agent imaging

Abstract

A new transducer for superharmonic and subharmonic contrast imaging was designed. This transducer was constituted of two elements: the outer low frequency (LF) element was centered at 4 MHz while a high frequency element (HF) was centered at 14 MHz. The center element was pad printed using InSensor™ TF2100 PZT paste. The outer element was mould with Ferroperm™ Pz26 and a curved porous Ferroperm™ Pz37 was used as backing. Each piezoelectric element was characterized to deduce electromechanical performance with thickness coupling factor around 45%. After the assembly of the transducer, pulse echo and hydrophone measurements were performed showing a large bandwidth (70% at -3dB) of the HF element. Finally, experiments with BR14 ® microbubbles were performed. Both superharmonic and subharmonic components were successfully observed from microbubble responses. The wide bandwidth of HF allows the detection of five harmonics with a good sensitivity.

Optimization of Contrast-to-Tissue Ratio Through Pulse Windowing in Dual-Frequency “Acoustic Angiography” Imaging

“…Previously, Kruse and Ferrara used single-cycle and 10-cycle excitation pulses (Kruse and Ferrara 2005) while Bouakaz et al used two-cycle excitation pulses for superharmonic imaging (Bouakaz et al 2002). Alternatively, other researchers have used many-cycle pulses for imaging approaches relying on narrowband harmonics (Tang and Eckersley 2006; Guiroy et al 2013). …”

Visualization of Microvascular Angiogenesis Using Dual-Frequency Contrast-Enhanced Acoustic Angiography: A Review

“…Using one such transducer with 0.8 MHz transmit and 2.9 MHz receive, Bouakaz et al (2003) demonstrated high CTR with superharmonic imaging compared to second harmonic imaging in human contrast-enhanced echocardiography. Others have implemented confocal dual-element transducers in vitro (Guiroy et al 2013;Kruse and Ferrara 2005). Kruse and Ferrara (2005) performed superharmonic M-mode imaging with confocal pistons at 2.25 and 15 MHz for transmit and receive, respectively, while Guiroy et al (2013) designed a confocal device with 4 MHz transmit and 14 MHz receive and imaged in 2D by raster-scanning the transducer over the imaging target.…”

“…Others have implemented confocal dual-element transducers in vitro (Guiroy et al 2013;Kruse and Ferrara 2005). Kruse and Ferrara (2005) performed superharmonic M-mode imaging with confocal pistons at 2.25 and 15 MHz for transmit and receive, respectively, while Guiroy et al (2013) designed a confocal device with 4 MHz transmit and 14 MHz receive and imaged in 2D by raster-scanning the transducer over the imaging target.…”

A Dual-Frequency Colinear Array for Acoustic Angiography in Prostate Cancer Evaluation

“…Microbubbles are micron-sized gas bubbles that provide enhanced contrast of blood due to the large mismatch in acoustic impedance between the gas core and the surrounding medium, aiding in the identification of blood vessels. During the past decades, a variety of methods have been proposed for contrast agent-specific imaging including, but not limited to, harmonic imaging [15-17], pulse inversion [18, 19], subharmonic imaging [20], chirp reversal [19] and radial modulation [21]. Although some techniques use the second harmonic signal, it has been noted that the second harmonic can be non-specific to MCAs because tissues also generate second harmonics through nonlinear wave propagation.…”