Ultrasound Imaging Technology Enhanced with Golden Nanorods Encased in Polymer

Ultrasound technology could soon undergo a significant enhancement that would enable it to generate high quality, high-resolution images, due to the development of a new key material.

The material, which converts ultrasound waves into optical signals that can be used to produce an image, is the result of a collaborative effort by Prof. Vladislav Yakovlev, a professor in the department of biomedical engineering at Texas A&M University (College Station, USA), and researchers from King’s College London (UK), The Queen’s University Belfast (Ireland), and the University of Massachusetts Lowell (USA). Their study findings appear in the March 1, 2013, issue of the journal Advanced Materials.

The modified substance, known as a “metamaterial,” offers substantial advantages over traditional ultrasound technology, which generates images by transforming ultrasound waves into electrical signals, Prof. Yakovlev explained. Although that technology has advanced throughout the years similar to the improvement in sonogram images, it is still mostly constrained by bandwidth and sensitivity limitations, he noted. These limitations, he added, have been the chief obstacle when it comes to producing high-quality images that can serve as powerful diagnostic tools.

The metamaterial developed by Prof. Yakovlev and his colleagues 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), which is vital for generating very detailed images, Prof. Yakovlev said. “A high bandwidth allows you to sample the change of distance of the acoustic waves with a high precision,” Prof. Yakovlev noted. “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.”

Meaning, this new material may enable ultrasound devices to see what they have not yet been able to see. That advancement could significantly boost a technology that is utilized in a range of biomedical applications. In addition to being used for visualizing fetuses during regular and emergency care, ultrasound is used for diagnostic purposes in events of trauma and even as a means of breaking up tissue and accelerating the effects of drugs therapies.
Whereas this research is not yet ready for incorporation into ultrasound technology, it has effectively shown how conventional technology can be substantially enhanced by using the newly engineering material created by his team, Prof. Yakovlev reported. The substance, he noted, is comprised of golden nanorods embedded in a polymer called a polypyrrole. An optical signal is sent into this compound where it interacts with and is changed by incoming ultrasound waves before passing through the material. A detection device would then read the changed optical signal, analyzing the changes in its optical characteristics to process a higher resolution image, he clarified.

“We developed a material that would enable optical signal processing of ultrasound,” Prof. Yakovlev concluded. “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 restricting the bandwidth of the transducer, and its potential biomedical applications represent the first practical implementation of this metamaterial.”

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Texas A&M University
King’s College London
Queen’s University Belfast