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Newswise — Sound has a long history in medicine, from the earliest 19th century stethoscopes to the latest ultrasound techniques that image growing fetuses and beating hearts. These days, sound waves are emerging as the basis of many new medical technologies -- helping to deliver genes and drugs to specific tissues, detecting bacterial infections and kidney stones, trimming the prostate, and many other applications. Acoustics is also blending with other disciplines such as neuroscience to help people with speech and hearing problems.
Journalists are invited to discover the world of medical acoustics at the 157th meeting of the Acoustical Society of America (ASA), which convenes from May 18-22 at the Hilton Portland & Executive Tower in Portland, Oregon. Medical acoustics is only one theme represented in more than 1,100 talks and posters to be presented at the meeting. Overall, acoustics is a cross-section of diverse disciplines that also includes architecture, underwater research, psychology, physics, animal bioacoustics, music, noise control, and speech.
Included below is a sample of newsworthy research related to medical acoustics. Registration information for journalists can be found at the end of the release.
MEDICAL HIGHLIGHTS 1) Explosive Shock Waves Flex Skulls2) Pair of Bionic Ears Helps to Distinguish Left from Right3) Twinkle, Twinkle Little Kidney Stone4) Exploding Bubbles Trim the Prostate5) Gene-Laden Bubbles Help Grow New Blood Vessels6) Homing Bubbles Spot Biofilms
******************************************************************1) EXPLOSIVE SHOCK WAVES FLEX SKULLSOver Sunday breakfast one morning, physicist William Moss and his wife discussed a newspaper article about soldiers wounded in Iraq. The troops' modern body armor had failed to protect them against shock waves released by explosions, which cause traumatic brain injury (TBI). How blast waves damage the brain was a mystery, so Moss' wife, a neuroscientist, offered him a challenge: "you can simulate that, can't you?"
Using computer models at the Lawrence Livermore National Laboratory, Moss and colleagues Michael King and Eric Blackman of the University of Rochester have found evidence that mild shock waves have the potential to damage the brain by deforming the skull. The results may pave the way for better helmet designs.
Most brain injuries are caused by an impact with a hard object, as in a car crash. The head can experience 200 G's or more of acceleration, slamming the brain against the inner wall of the skull. Shock waves from explosions can also damage the brain, but the mechanism by which this happens is still poorly understood.
The researchers' simulation of a blast wave shows that it causes less acceleration of the head over a shorter period of time compared to an impact. But the blast also appears to deform and flex the hard skull, creating ripples that generate large pressure variations in the brain, resulting in damage that may be just as severe as that caused by an impact.
If further experiments confirm this mechanism, helmets could be redesigned to minimize blast-related traumatic brain injury. Modern helmets are held on the head either by webbing, which can allow shock waves to pass through the air between the helmet and head, or by foam pads, which can become stiff under a blast, and transfer the shock wave to the skull. Suspension systems that block the gap between the helmet and the skull, and also prevent forces on the helmet from being transferred to the skull could help future helmets provide better protection against blast waves.
The talk "Skull flexure from blast waves: A mechanism for brain injury with implications for helmet design" (3pBB5) by William Moss et al is at 1:45 p.m. on Wednesday, May 20, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa720.html.
******************************************************************2) PAIR OF BIONIC EARS HELPS DISTINGUISH LEFT FROM RIGHTCan a pair of bionic ears benefit a hearing-impaired child? Cynthia Zettler, a postdoctoral fellow in Ruth Litovsky's laboratory at the University of Wisconsin-Madison thinks so. In Portland, she and her colleagues will present initial data from a five year longitudinal study of children suggesting that over the course of years implants can partially restore a child's ability to identify what direction a sound is coming from.
Several decades ago, the first cochlear implant -- a bionic ear that works by directly stimulating auditory nerves -- was surgically implanted in a hearing-impaired adult. But only within the last decade has the U.S. Food and Drug Administration approved the use of cochlear implants in both ears. Now more than 5,000 children have received these "bilateral" implants, which have been shown to help infants acquire language and to improve quality of life for hearing-impaired children.
The research team investigated whether the devices could also restore the 'ability of children to localize sounds they encounter in their daily lives. The researchers played a moving human voice through speakers placed at different points around a child, and asked the child whether the voice was coming from the left or the from the right. The children best able to identify the directionality of the sound -- typically the oldest who had been wearing the implants for the longest amount of time -- performed almost as well as children born with normal hearing. They could discriminate left from right until the voice was almost directly in front.
But not all of the children performed this well. As fundamental as the ability to distinguish left from right seems to people born with normal hearing, some of the children with bilateral implants could never discriminate left from right, even when the voices were directly to the side. Zettler believes that there may be an adjustment period for the brain to adapt to the implants. As the study continues, she hopes to pin down the factors that determine why the implants work better for some children than for others.
The poster "Minimum audible angles in children who use bilateral cochlear implants" (4pPP17) by Cynthia Zettler et al is at 1:00 p.m. on Thursday, May 21, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa969.html
******************************************************************3) TWINKLE, TWINKLE LITTLE KIDNEY STONEDoppler ultrasound uses reflected sound waves to detect motion in blood vessels, painting them blue or red depending on the direction of blood flow. It is not designed to spot kidney stones, but -- for reasons still poorly understood -- stones confuse the machine and show up in scans as a twinkle of rainbow colors. Urologist Anup Shah of the University of Washington, Seattle, and a team of researchers will present data suggesting that this spurious artifact could provide a better way to detect kidney stones.
Kidney stone diagnosis starts with a CT scan, a high-resolution image created with X-ray radiation that is not done in the urologist's office. Another technique called fluoroscopy provides low-resolution snapshots at five minute intervals to target lithotripsy, a treatment that breaks up the stone with sound waves. Traditional ultrasound has been investigated as a third technique for spotting stones, but its success rate is less than 25 percent.
To see if Doppler ultrasound could provide a cheaper and safer way to spot stones in real time, Shah conducted studies which resulted in a 100 percent detection rate. Others have had a success rate around 80 percent. To improve this detection efficiency, Shah's team is investigating why and at which wavelengths the stones twinkle. Instead of a clean echo, the twinkle seems to be a mess of shear waves and reverberations created by the stone's rough edges but not by the surrounding soft tissue.
"We now have the tools to tailor an ultrasound imager to pick up kidney stones," says Shah. The research is partially funded by NASA, which hopes to provide astronauts with a way to detect stones on long space voyages. CT and MR machines are too bulky to haul up into space, but ultrasound machines are fairly small and portable -- the International Space Station has one on board.
The talk, "Investigation of an ultrasound imaging technique to target kidney stones in lithotripsy" (3aBB1) by Anup Shah is at 8:00 a.m. on Wednesday, May 20, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa596.html
******************************************************************4) EXPLODING BUBBLES TRIM THE PROSTATEIn the traditional surgical treatment for prostate growths, a rigid instrument is inserted through the penis and used to scrape away cells lining the walnut-sized gland. Urologist William Roberts and a team at the University of Michigan, Ann Arbor, are developing a less invasive way to remove tissue using focused pulses of ultrasound. Their technique, histotripsy, has now been used to safely trim the interiors of aging prostates in the body.
Unlike other therapeutic ultrasound technologies in development, which create heat to boil pathogenic tissue, histotripsy mechanically breaks apart tissue with shorter, strong pulses of ultrasound. These pulses create tiny bubbles out of dissolved gas in prostate tissue. As the bubbles violently collapse, they release tiny shock waves, a phenomena called acoustic cavitation. Over tens of thousands of pulses, the combined force of these cavitations liquefies nearby tissue into slurry that passes out through the penis. This tissue excavation can be monitored and targeted in real time with acoustic imaging.
"Historically, no one believed that cavitation could be controlled like this. We're the only group doing this kind of work," says Roberts. His team used the technique to dissolve marble-sized chunks of cells in the walls of prostates. Side effects common in traditional prostrate treatments -- bleeding and inflammation -- were minimal after histotripsy treatment, as were signs of discomfort. Roberts hopes to develop histotripsy into a clinical treatment for early-stage cancer and enlarged prostate (BPH).
The talk, "Histotripsy: Urologic applications" (3pBB3) by William Roberts is at 1:15 p.m. on Wednesday, May 20, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa718.html
******************************************************************5) GENE-LADEN BUBBLES HELP GROW NEW BLOOD VESSELSProgress in human gene therapy -- the insertion of therapeutic DNA into diseased tissue -- has been slower than expected since the first clinical trials in 1990. One of the biggest challenges for this technology is finding ways to safely and effectively deliver genes only to the specific parts of the body that they are meant to treat. Cardiologist Jonathan Lindner of Oregon Health & Science University will discuss his latest experiments in gene therapy that use microscopic bubbles chemically modified to stick to the cells that line blood vessels.
This technique, ultrasound-mediated gene delivery (UMGD), exploits the properties of contrast agents, microparticles that are normally injected into the body to improve the quality of ultrasound images. In UMGD, the tiny particles are microbubbles composed of pockets of gas encapsulated by thin membranes that are coated with DNA before injection. A targeted pulse of ultrasound energy "rings" the bubbles like a bell, popping them in a specific location and releasing the DNA into the surrounding tissue.
To improve the specificity of this targeting, Lindner grafts long arm-like molecules to the outside of the bubbles. These arms, which do not interfere with the DNA attached to surface, are designed recognize and bind to molecules on the outside of specific cells in the body, allowing the bubbles to first attach to tissue before being popped. In theory, this should improve both the specificity and efficiency of the gene therapy.
Lindner created an arm designed to attach to endothelial cells lining blood vessels. He will present data evaluating the behavior of these "targeted" bubbles in living tissue. The ability to stick these gene-laden microbubbles to the lining of blood vessels increased the amount of gene transfection. This strategy may be particularly important for delivering therapeutic DNA to the walls of blood vessels. For example, Lindner and collaborators have successfully stimulated the growth of new blood vessels using UMGD with microbubbles carrying a gene for vascular endothelial growth factor (VEGF). This therapeutic use could be important for treating people who have heart attacks, peripheral artery disease, or stroke.
The team is also investigating using the bubbles to transport small doses of drugs. "If you're trying to deliver a nasty drug to part of the body, this may be a way to improve safety," says Lindner.
The talk "Targeted microbubble technology and ultrasound-mediated gene delivery" (4aBB2) by Jonathan Lindner is at 8:20 a.m. on Thursday, May 21, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa791.html
******************************************************************6) HOMING BUBBLES SPOT BIOFILMSSome kinds of bacteria can join forces to form protective communities called biofilms. These thin layers of bacteria, which grow on the surfaces of medical implants or directly on tissue in the body, can be difficult to treat because they are more resistant to drugs than the bacteria on their own. Currently there is no established way to image biofilms in or out of the body.
Pavlos Anastasiadis and colleagues at the University of Hawaii at Manoa have developed a method to watch and measure growing biofilms with ultrasound. The researchers used contrast agents, microparticles that are normally injected into the body to improve the quality of ultrasound images. They modified the surface of bubbles in the agents to stick to two kinds of infectious bacteria that form biofilms. Acoustic pulses of ultrasound cause the bubbles to "ring" like a bell, revealing their location and the attached biofilm.
The research was done on isolated biofilms. The next step will be to test it in living tissue. Anastasiadis hopes to develop the technique to diagnose infective endocarditis, a disease in which bacterial biofilms form on the inner walls of damaged heart valves.
The talk "Targeted ultrasound contrast agents for the imaging of biofilm infections" (2aBB10) by Pavlos Anastasiadis is at 10:45 a.m. on Tuesday, May 19, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa323.html
******************************************************************WEBSITES OF INTEREST / MORE INFORMATIONMain meeting website is http://asa.aip.org/portland/information.html. Full meeting program is http://asa.aip.org/portland/program.html. Searchable meeting program is http://asa.aip.org/asasearch.html.
WORLD-WIDE PRESS ROOMThe ASA's World Wide Press Room (http://www.acoustics.org/press) is now updated with the new content for the 157th ASA meeting in Portland. It contains tips on dozens of stories as well as nearly 40 lay-language papers detailing some of the most newsworthy results at the meeting. Lay-language papers are roughly 500 word summaries written for a general audience by the authors of individual presentation with accompanying graphics and multimedia files. They serve as starting points for journalists who are interested in covering the meeting but cannot attend in person.
PRESS REGISTRATIONJournalists are welcome to attend the conference free of charge. We will grant free registration to any credentialed full-time journalist or professional freelance journalist working on assignment for a major publication or outlet. If you are a reporter and would like to attend, please contact Jason Bardi ([email protected], 858-775-4080). He can also help with setting up interviews or obtaining images, sound clips, or background information.
ABOUT THE ACOUSTICAL SOCIETY OF AMERICAThe Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science of technology of sound. Its 7,500 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world's leading journal on acoustics), Acoustics Today magazine, ECHOES newsletter, books and standards on acoustics. The society also holds two major scientific meetings each year. For more information about ASA, visit our website at http://asa.aip.org.
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