Helped by Metamaterial, Ultrasound Makes it Through Bone with Little Distortion
 

Helped by Metamaterial, Ultrasound Makes it Through Bone with Little Distortion
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Ultrasound is a great imaging modality that’s also used in a number of therapeutic applications. Its advantages include being able to penetrate tissue without using ionizing radiation, as well as the ability to see moving objects in real-time. A serious limitation, though, is that ultrasound waves*are dispersed when they meet a hard object on the way to their real target. This, for example, makes **n-invasive monitoring of blood flow in the brain and ultrasound targeting of brain tumors particularly difficult. Researchers from***rth Carolina State University and*Massachusetts Institute of Tech**logy have seemingly overcome this limitation that may open new doors for ultrasound in clinical use.

The technique relies on a special metamaterial that restores the sound waves that have been affected by the dense material in the way of the target. The technique has only been tested in a computer simulation so far, but the researchers are already building a prototype that will take advantage of the metamaterial. In the simulation, 28% of energy was able to make it past a layer of bone, while 88% made it through when taking advantage of the metamaterial.

Details from the study abstract:

In this paper, we investigate a type of anisotropic, acoustic complementary metamaterial (CMM) and its application in restoring acoustic fields distorted by aberrating layers. The proposed quasi two-dimensional (2D), **nresonant CMM consists of unit cells formed by membranes and side branches with open ends. Simultaneously, anisotropic and negative density is achieved by assigning membranes facing each direction (x and y directions) different thicknesses, while the compressibility is tuned by the side branches. Numerical examples demonstrate that the CMM, when placed adjacent to a strongly aberrating layer, could acoustically cancel out that aberrating layer. This leads to dramatically reduced acoustic field distortion and enhanced sound transmission, therefore virtually removing the layer in a **ninvasive manner. In the example where a focused beam is studied, using the CMM, the acoustic intensity at the focus is increased from 28% to 88% of the intensity in the control case (in the absence of the aberrating layer and the CMM). The proposed acoustic CMM has a wide realm of potential applications, such as cloaking, all-angle antireflection layers, ultrasound imaging, detection, and treatment through aberrating layers.

Study in Physical Review X:*Anisotropic Complementary Acoustic Metamaterial for Canceling out Aberrating Layers…

NC State:*New Technique Allows Ultrasound To Penetrate Bone, Metal…

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