Treating Burn Wounds Gently

A new ultrasound imaging technique that does not require contact with the patient's body may soon enable physicians to assess burn injuries with greater accuracy. The device was described earlier this month at a meeting of the Acoustical Society of America in Columbus, Ohio.

Physicians mainly rely on visual inspection to gauge the severity of burns, an approach that often forces them to guess whether the blood vessels underneath the burn are damaged. Waiting for the extent of the damage to reveal itself in further symptoms can leave patients in excruciating pain; moreover, if damaged blood vessels are not replaced by a skin graft, they will never heal properly. Ultrasound imaging, in which sound waves are bounced off internal body structures to create a picture, would allow a faster, accurate diagnosis. But it involves pressing a so-called transducer against the skin, an unbearable procedure for burn patients.

Physicist Joie Jones and his colleagues at the University of California, Irvine, set out to develop an ultrasound device that could be held close to a patient's skin, kind of like the diagnostic wand used in Star Trek. "People thought we were crazy to try it," Jones says. When an ultrasound transducer is held above the skin, the difference in impedance--or resistance to sound waves--between the device and the air is so great that most of the sound is echoed back before it ever reaches the skin. The team overcame this problem by coating the transducer with layers of oxygen-containing polymers; each layer's impedance was a little closer to that of the air, allowing the sound waves to travel smoothly to the skin. The team found that the transducer worked as far away as 6 centimeters from the patient's skin.

Bruce Achauer, director of the burn unit at Irvine, has used a prototype of the device to evaluate burns in about 100 patients. "We were blown away," he says. The new device doesn't deliver images yet, but researchers can deduce the extent of vessel damage from the data. "Its predictions tracked closely with the patients' clinical outcome," says Achauer.

Jones says the device, which is small, portable, and easy to use, could be a boon not only to emergency rooms and burn centers, but to ambulance teams as well. Achauer agrees: "Burn patients could be treated so much more quickly and successfully if this type of technology were widely available."