Dual-Frequency Piezoelectric Endoscopic Transducer for Imaging Vascular Invasion in Pancreatic Cancer

Abstract

Cancers of the pancreas have the poorest prognosis among all cancers, as many tumors are not detected until surgery is no longer a viable option. Surgical viability is typically determined via endoscopic ultrasound imaging. However, many patients who may be eligible for resection are not offered surgery due to diagnostic challenges in determining vascular or lymphatic invasion. In this article, we describe the development of a dual-frequency piezoelectric transducer for rotational endoscopic imaging designed to transmit at 4 MHz and receive at 20 MHz in order to image microbubble-specific superharmonic signals. Imaging performance is assessed in a tissue-mimicking phantom at depths from 1.0 cm (CTR = 21.6 dB) to 2.5 cm (CTR = 11.4 dB), in ex vivo porcine vessels, and in vivo in a rodent. The prototyped 1.1 mm-aperture transducer demonstrates contrast-specific imaging of microbubbles in a 200 μm-diameter tube through the wall of a ~1 cm-diameter porcine artery, suggesting such a device may enable direct visualization of small vessels from within the lumen of larger vessels such as the portal vein or superior mesenteric vein.

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 .…”

First-in-Human Study of Acoustic Angiography in the Breast and Peripheral Vasculature

“…Though it is estimated that 30% of breast lesions are located within 1 cm of the skin surface, a larger imaging depth will be necessary to make superharmonic contrast imaging feasible relevant to a greater number of patients (Feig, et al 1977). Acoustic angiography can be performed with greater depth of penetration by selecting a lower receive frequency, and we have demonstrated superharmonic contrast imaging as deep as 4 cm using an endoscopic transducer designed to transmit at 4 MHz and receive at 20 MHz (Lindsey, et al 2017). Axial resolution at this frequency combination is expected to be better than 200 μm (Lindsey, et al 2014).…”

Functional micro/nanobubbles for ultrasound medicine and visualizable guidance

“…Surgical viability typically relies on endoscopic ultrasound. Jiang [110] described the development of a dual-frequency piezoelectric transducer for rotational endoscopic imaging and the visualization of MBs-specific superharmonic signals. It may enable direct visualization of small vessels from within the lumen of larger vessels such as the portal vein or superior mesenteric vein (Figure 13).…”

“…Combined 3D rendering of Bmode (grayscale) and dual-frequency (red) imaging volumes shows contrast-specific signal originates only from MBs within the tube in (e) short and (f) long-axis views (Scale bar=2 mm). (Reproduced from Ref [110]. with the permission of Medscape Ltd.) (color online).…”