Sound bullets could treat cancers and replace ultrasound (w/ Video)

Apr 07, 2010 by Lin Edwards report
Newton's cradle

(PhysOrg.com) -- Acoustic devices are used in a range of applications such as ultrasound scanners, but their performance is limited for some uses by their inaccurate focusing and low focal power. Now a group of scientists in the US have developed an acoustic lens that can focus acoustic waves with greater energy than ever before possible to produce "sound bullets" that could find many uses, including effective, nonintrusive sonic scalpels for destroying tumors or kidney stones.

Researchers, Alessandro Spadoni, from Graduate Aerospace Laboratories, and Chiara Daraio of Applied Physics, at the California Institute of Technology, at Pasadena, California, designed the new acoustic lens for use in medical applications. The high pressure induced by the compact acoustic pulses, or sound bullets, causes the temperature at the focal point to rise, so the bullets could be used to burn tissue without affecting surrounding tissues. If modulated differently, it could also be used to produce near photo-quality images of the inside of the body, but without the radiation risks of X-rays.

The new acoustic lens is made of a metamaterial and uses the Newton’s cradle principle, which is familiar to many people from a toy with identical metal balls suspended on strings, designed to demonstrate the conservation of energy. When the ball at one end is pulled out and released, the ball at the other end swings out at the same speed. The metamaterial comprises 21 parallel chains, each containing 21 stainless steel spheres, but instead of channeling motion, the balls channel , which are converted to a shock wave called a “solitary wave”. The energy leaving the lens does not bounce back through the chains because of the length of the chains, and instead is focused on a spot a few centimeters in front of it.

Combined DP/FE model. (A) Arrays of spheres interact with a baffle (orange lines) which in turn interacts with the adjacent fluid. (B) The interaction of granular media and baffle. Image: Spadoni et al. 10.1073/pnas.1001514107

Professor Daraio said the conversion of sound to a solitary wave is essential because solitary waves are easier to control than sound, and enabled them to achieve high focal intensities in the sound wave emitted, and its position could be controlled without needing to change the lens structure. Daraio said that if the outer chains are squeezed together closer than the inner chains, the solitary waves travel faster in the outer chains, resulting in successive sound pulses. The scientists can also adjust the intensity of the sound bullets emitted, so they can be powerful enough to be used as sonic scalpels or gentle enough for internal body imaging. The latter use would be an improvement on ultrasound because the sound is more highly focused, and can be repositioned easily.

This video is not supported by your browser at this time.
Stress waves traveling in a nonlinear acoustic lens and sound bullet formation in the adjacent fluid medium (numerical results). In the lens, the sphere colors are proportional to the contact-force amplitude. Waves emitted by the nonlinear acoustic lens reach the host medium (via an elastic interface), where they generate compact spherical pressure waves. The pressure waves coalesce in the host medium and form a sound bullet. The color bar on the right represents the scale of pressure intensity (Pa) in the host medium.

The system is still under development and has not yet been tested on living cells. It is likely to be some years before it is available for medical or other applications.

The research paper is published in this week’s issue of the Proceedings of the National Academy of Sciences journal.

Explore further: Single laser stops molecular tumbling motion instantly

More information: Alessandro Spadoni and Chiara Daraiob, Generation and control of sound bullets with a nonlinear acoustic lens, Published online before print April 5, 2010, doi:10.1073/pnas.1001514107

Related Stories

First acoustic metamaterial 'superlens' created

Jun 24, 2009

A team of researchers at the University of Illinois has created the world's first acoustic "superlens," an innovation that could have practical implications for high-resolution ultrasound imaging, non-destructive ...

First hyperlens for sound waves created

Oct 25, 2009

Ultrasound and underwater sonar devices could "see" a big improvement thanks to development of the world's first acoustic hyperlens. Created by researchers with the U.S. Department of Energy's Lawrence Berkeley ...

Mathematicians find way to improve medical scans

Jan 07, 2008

Mathematicians at the University of Liverpool have found that it is possible to gain full control of sound waves which could lead to improved medical scans, for technology such as ultra sound machines.

Nothing but first-class seats at the movies

Jul 05, 2006

Invisible, but audible, is the latest attraction at the Bavaria Film Studios near Munich. The "4D cinema experience" is the second movie theater in Germany to have departed from conventional multi-channel sound. ...

Recommended for you

New method for non-invasive prostate cancer screening

4 hours ago

Cancer screening is a critical approach for preventing cancer deaths because cases caught early are often more treatable. But while there are already existing ways to screen for different types of cancer, ...

How bubble studies benefit science and engineering

5 hours ago

The image above shows a perfect bubble imploding in weightlessness. This bubble, and many like it, are produced by the researchers from the École Polytechnique Fédérale de Lausanne in Switzerland. What ...

Famous Feynman lectures put online with free access

6 hours ago

(Phys.org) —Back in the early sixties, physicist Richard Feynman gave a series of lectures on physics to first year students at Caltech—those lectures were subsequently put into print and made into text ...

Single laser stops molecular tumbling motion instantly

10 hours ago

In the quantum world, making the simple atom behave is one thing, but making the more complex molecule behave is another story. Now Northwestern University scientists have figured out an elegant way to stop a molecule from ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Birger
not rated yet Apr 07, 2010
Aren't solitons conceptually related to tsunami waves?