Metamaterial brings extra clarity to ultrasound images

2 min read

Scientists at King’s College London have developed a new material that could lead to considerable improvements in ultrasound technology, enabling the production of high-quality, high-resolution images in biomedical applications.

The researchers have engineered a metamaterial which converts ultrasound waves into optical signals and is claimed to offer significant advantages over conventional ultrasound technology, which itself relies on generating images by converting ultrasound waves into electrical signals.

The research, published in Advanced Materials, is led by Dr Wayne Dickson in the Department of Physics at King’s in collaboration with fellow King’s physicist Prof Anatoly Zayats and colleagues at Texas A&M, Queen’s University Belfast and University Massachusetts Lowell.

In a statement Dr Dickson said, ‘The high bandwidth allows you to sample the change of distance of the acoustic waves with high precision. Greater sensitivity enables you to see deeper in tissue, producing visuals in much greater detail than is currently possible.

‘The greater sensitivity and broader bandwidth means we can go from 0-150MHz without sacrificing sensitivity. Current technology typically experiences a substantial decline in sensitivity around 50MHz. This means the metamaterial can efficiently convert an acoustic wave into an optical signal without limiting the bandwidth of the transducer, offering exciting potential in biomedical applications.’

The continued development of existing ultrasound technology is said to have been constrained by bandwith restrictions and sensitivity limitations, which have up until now been the primary obstacle when it comes to producing high-quality images that can serve as powerful diagnostic tools.

The metamaterial developed by Dr Dickson 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) – an important concept for producing highly detailed images.

This means that this new metamaterial may enable ultrasound devices to see previously undetectable detail, an advancement that could significantly bolster a technology that is employed in a variety of biomedical applications. It is well known in visualising foetuses during routine and emergency care and for diagnostic purposes in incidents of trauma. It can also be a means of breaking up tissue and accelerating the effects of drugs therapies.

While these advances are not yet ready for integration into ultrasound technology, Dr Dickson and his team have successfully demonstrated how conventional technology can be substantially improved by using the newly engineered material created by the team.

The metamaterial consists of gold nanorods embedded in Polypyrrole (PPy).  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, analysing the changes in its optical properties to process a higher resolution image.

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The paper, published in Advanced Materials, is available here.