Contrast Enhanced Superharmonic Imaging for Acoustic Angiography Using Reduced Form-Factor Lateral Mode Transmitters for Intravascular and Intracavity Applications

Abstract

Techniques to image the microvasculature may play an important role in imaging tumor-related angiogenesis and vasa vasorum associated with vulnerable atherosclerotic plaques. However, the microvasculature associated with these pathologies is difficult to detect using traditional B-mode ultrasound or even harmonic imaging due to small vessel size and poor differentiation from surrounding tissue. Acoustic angiography, a microvascular imaging technique which utilizes superharmonic imaging (detection of higher order harmonics of microbubble response), can yield a much higher contrast to tissue ratio (CTR) than second harmonic imaging methods. In this work, two dual-frequency transducers using lateral mode transmitters were developed for superharmonic detection and acoustic angiography imaging in intracavity applications. A single element dual-frequency IVUS transducer was developed for concept validation, which achieved larger signal amplitude, better contrast to noise ratio (CNR) and pulse length compared to the previous work. A dual-frequency PMN-PT array transducer was then developed for superharmonic imaging with dynamic focusing. The axial and lateral size of the microbubbles in a 200 μm tube were measured to be 269 μm and 200 μm, respectively. The maximum CNR was calculated to be 22 dB. These results show that superharmonic imaging with a low frequency lateral mode transmitter is a feasible alternative to thickness mode transmitters when final transducer size requirements dictate design choices.

Ultrasound-Stimulated Phase-Change Contrast Agents for Transepithelial Delivery of Macromolecules, Toward Gastrointestinal Drug Delivery

“…The prospect of highfrequency and therefore high-resolution image guidance may be particularly advantageous for small animal studies where anatomical features are difficult to resolve with relatively low-frequency imaging. Dual frequency transducers are currently under development for contrast-enhanced intravascular and intracavity imaging (Kim, et al 2015, Lindsey, et al 2017, Wang, et al 2017, which could be modified for image-guided therapy purposes. A dual frequency approach can also be employed to initiate PCCA phase change at high frequency and detect the unique acoustic signature of PCCA vaporization at low frequency .…”

A Review of Electric Impedance Matching Techniques for Piezoelectric Sensors, Actuators and Transducers

“…The electric impedance of the transducer is inversely proportional to the capacitance at resonance. Transmission line theory allows the coaxial cable to be modeled as an impedance transformer matching the impedance to the electronics [166]. This reduces the reflections and increases the power delivery.…”

A Micromachined Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystal Composite Circular Array for Intravascular Ultrasound Imaging

“…The primary results showed potential as a good candidate for receiving transducer array to the vasa vasorum assessment. The technique, as known as acoustic angiography, utilizes the ultrabroadband responses of contrast agents, exciting them near 2-5 MHz range, and receiving harmonics at >20 MHz [44,45]. This provides a very high signal to noise, highresolution contrast imaging, which enable us to acquire the exceptional sensitivity to microvessel structural mapping.…”