New technique allows ultrasound to pass through metal and bone

Ultrasound imaging is one of the most commonly used methods of medical diagnosis and treatment. It works by emitting high frequency audio waves; when these waves bounce off an object, they return to the ultrasound equipment. This equipment then translates the waves into an image. However, certain materials, such as bone or metal, have particular characteristics that block or distort ultrasound waves. The presence of these materials, known as aberrating layers, can decrease the accuracy and effectiveness of ultrasound imaging.

A new technique developed by researchers in the College solves this problem by using customized structures that compensate for the distortion usually caused by aberrating layers.

"In effect, it's as if the aberrating layer isn't even there," says Dr. Yun Jing, an assistant professor of mechanical and aerospace engineering.

In order to address the problem of aberrating layers, the researchers designed customized metamaterial structures that can account for and offset the acoustic properties of the aberrating layer. These metamaterial structures use a series of membranes and small tubes to achieve the desired acoustic characteristics.

This new technique has been tested by the researchers using computer simulations with impressive results. In these simulations, only about 28 percent of sound wave energy makes it past an aberrating layer of bone without the metamaterial structure in place. With the metamaterial structure, however, 88 percent of ultrasound wave energy passes through the aberrating layer.

This technique is a significant development for the use of ultrasound imaging in both medical and industrial settings.

"… (This) will make it easier for medical professionals to use ultrasound imaging for diagnostic or therapeutic applications, such as monitoring blood flow in the brain or to treat brain tumors. This has been difficult in the past because the skull distorts the ultrasound's acoustic field." - says Tarry Chen Shen, a Ph.D. student in the Department of Mechanical and Aerospace Engineering and lead author of a paper on the work.

According to Jing, the technique can also be used in industrial settings by allowing for the detection of cracks in airplane wings under the wing's outer layer of metal.

SOURCE

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