Shedding light on the body's interior.

Normally shining a light through an animal - especially bulky ones like rats or people - reveals very little about what's inside. But a technique called optical time-of-flight and absorbance imaging (TOFA) lets researchers view not only organs, but also gas inside those organs.

The technique is one of several being developed that carefully process light to get more information from it (SN: 12/5/92, p.398). TOFA makes images by timing individual photons from three diode lasers. The time it takes for a given fraction of photons to pass through a part of the animal varies depending on the tissue in the path of the light, says David A. Benaron of Stanford University School of Medicine.

Through relatively simple computations, the instrument's microprocessor converts the variable time periods to a color scale and then generates the images, Benaron and Stanford colleague David K. Stevenson report in the March 5 SCIENCE.

The Stanford group is trying more powerful lasers to improve the speed and resolution of this technique, which they say shows promise as a portable, easy-to-use medical imaging tool. Already, TOFA seems capable of determining whether oxygen is reaching tissue deep in the body and consequently may aid in early detection of brain injury Benaron says. In addition, it may one day monitor glucose and cholesterol in blood or be adapted for use in industry