King's College London

Material may let ultrasound ‘see’ like never before

TEXAS A&M (US) — Ultrasound technology could get a significant upgrade from a new material that converts ultrasound waves into optical signals to produce high-quality, high-resolution images.

The technology offers significant advantages over conventional ultrasound technology, which generates images by converting ultrasound waves into electrical signals.

Although that technology has advanced throughout the years—think of the improvement in sonogram images—it is still largely constrained by bandwidth and sensitivity limitations. These limitations have been the chief obstacle when it comes to producing high-quality images that can serve as powerful diagnostic tools, researchers say.


An optical signal, represented by the red arrow, comes into contact with the metamaterial and interprets the ultrasound waves, resulting in an altered optical signal that is processed to produce a high-quality image. (Credit: Texas A&M University)

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The new “metamaterial” is not subject to those limitations, primarily because it converts ultrasound waves into optical signals rather than electrical ones. The optical processing of the signal does not limit the bandwidth or sensitivity of the transducer (converter)—and that’s important for producing highly detailed images, says Vladislav Yakovlev, professor at Texas A&M University.

“A high bandwidth allows you to sample the change of distance of the acoustic waves with a high precision. This translates into an image that shows greater detail. Greater sensitivity enables you to see deeper in tissue, suggesting we have the potential to generate images that might have previously not been possible with conventional ultrasound technology.”

In other words, the new material may let ultrasound devices to see what they haven’t yet been able to see. That advancement could significantly bolster a technology that is employed in a variety of biomedical applications.

In addition to being used for visualizing fetuses during routine and emergency care, ultrasound is used for diagnostic purposes in incidents of trauma and even as a means of breaking up tissue and accelerating the effects of drugs therapies.

While the research, published in the journal Advanced Materials, is not yet ready for integration into ultrasound technology, Yakovlev says it successfully demonstrates how conventional technology can be substantially improved.

The material consists of golden nanorods embedded in a polymer known as polypyrrole. An optical signal is sent into this material where it interacts with and is altered by incoming ultrasound waves before passing through the material. A detection device would then read the altered optical signal, analyzing the changes in its optical properties to process a higher resolution image, Yakovlev explains.

“We developed a material that would enable optical signal processing of ultrasound,” he says. “Nothing like this material exists in nature so we engineered a material that would provide the properties we needed. It has greater sensitivity and broader bandwidth. We can go from 0-150 MHz without sacrificing the sensitivity. Current technology typically experiences a substantial decline in sensitivity around 50 MHz.

“This metamaterial can efficiently convert an acoustic wave into an optical signal without limiting the bandwidth of the transducer, and its potential biomedical applications represent the first practical implementation of this metamaterial.”

Researchers from King’s College London, the Queen’s University of Belfast, and the University of Massachusetts Lowell contributed to the study.

Source: Texas A&M University

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