For better imaging

The development of a new material will improve ultrasound techniques

Published: Tuesday 29 February 2000

ultrasound imaging has proved to be immensely useful in the diagnosis of illnesses. It is supposed to be safe and relatively inexpensive and gives the physician a clear picture of organs that x -rays cannot image, such as the liver and the pancreas gland. However, it cannot be used in cases where physical contact between the patient's body and the imaging device is not possible. This can be the case when a patient has serious burns. Even magnetic resonance imaging ( mri ) is too slow and cumbersome in these cases. What is required is a quick and painless way of determining the extent of burns under the skin and whether the patient needs surgery. A group of scientists has recently reported the development of a technique that will make it possible to obtain an ultrasound image without contact with the body.

The reason conventional ultrasound devices need physical contact is because the ultrasound wave generated in the machine is sent through the air into the body, causing a large proportion of the waves to be reflected back into the device. This happens because the quantity of the air's 'impedance' is very different from that of the device producing the waves. Impedance is the product of the velocity of the sound in the media and the density of the substance. If the impedance of the device and the surrounding air is more closely matched, then it is possible that a larger amount of ultrasound energy will enter the body and not get reflected back.

This is precisely what Joie Jones of the University of California in Irvine, usa , and his colleagues have done. They have devised a layered material in which each layer has an impedance that is closer to that of air. In this fashion, the ultrasound waves do not get reflected back but pass into the patient's body. The researchers have tested the device on about a hundred patients. They have managed to obtain images with the device positioned about five cm away from the body. They feel that once they can conduct extensive clinical trials on the device, they would be able to provide images for patients on whom conventional ultrasound cannot be performed.

Subscribe to Weekly Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.