Number 456 (Story #1), November 9, 1999 by Phillip F. Schewe and Ben Stein|
ULTRASOUND IMAGING WITHOUT PHYSICAL CONTACT between device and patient has been achieved, providing a potential solution to an unmet medical need--determining the depth and severity of serious burns in a convenient, accurate, and pain-free fashion. At the present time, physicians usually diagnose burns by inspecting them visually; however, such visual observation cannot provide direct information on whether there is damage to underlying blood vessels, a condition which requires surgery. Technologies such as conventional ultrasound or MRI are either too slow, time-consuming, or cumbersome. In addition, they are painful for the patient if they require direct contact with the burn area. This is certainly the case with conventional ultrasound, which requires direct contact with the body, or must at least be connected to the body via water. That's because generating ultrasound in a device and sending it through air causes a large proportion of the sound to bounce right back into the device. This results from a great mismatch between air and the device in the values of their "impedance," the product of the density of the substance and the velocity of sound through it. By more closely matching the impedance values between the device and air, a significantly greater proportion of sound can be transmitted to the body, and reflected back, to obtain enough of a signal for an image. In a non-contact ultrasound device described at last week's meeting of the Acoustical Society of America in Columbus, Joie Jones of UC-Irvine (949-824-6147, email@example.com) and his colleagues pass the sound wave through a multilayered material, with each succeeding layer having an impedance value closer to that of air. The transmission is improved to the point that the researchers could image burns by holding their device about two inches away from the skin, in about a minute or so. Having tested this device on over 100 patients, the researchers plan to move to larger clinical studies and develop a device that can take images in real time.
See images at Physics News Graphics