Oncology

Medical Acoustics Highlights Of The 157th ASA Meeting, May 18-22 In Portland

Bionic ears, bubbles, blast waves and biofilms 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. 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. MEDICAL HIGHLIGHTS * Explosive Shock Waves Flex Skulls * Pair of Bionic Ears Helps to Distinguish Left from Right * Twinkle, Twinkle Little Kidney Stone * Exploding Bubbles Trim the Prostate * Gene-Laden Bubbles Help Grow New Blood Vessels * Homing Bubbles Spot Biofilms 1) EXPLOSIVE SHOCK WAVES FLEX SKULLS Over 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 RIGHT Can 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 STONE Doppler 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 PROSTATE In 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 VESSELS Progress in human gene therapy -- the insertion of therapeutic DNA into diseased tissue -- has been slower

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