Quick and easy pictures of health

A photodetector that picks up minute temperature changes could be a simple way to diagnose breast cancer

Physicists from the Fraunhofer Institute for Applied Solid State Physics in Freiburg have been instrumental in developing an infrared camera that offers a painless and reliable diagnosis for breast cancer. At its heart is a new type of quantumwell infrared photodetector, the so-called low noise Qwip, developed in Freiburg, which can detect the tiniest of temperature changes in human tissue.

A growing tumour changes the temperature of tissue and skin. But to obtain a definite cancer diagnosis by thermography, temperature deviations of just a few millidegrees must be measured accurately, and temperature variations have to be monitored for a few seconds.

The new generation of detector can spot temperature changes of 0.0050C, says Harald Schneider, a member of the project and inventor of the improved detector. The basis for it is a semiconductor chip made of gallium-arsenide, which can accommodate 640 x 512 pixels on the size of a fingernail.

The detector has been incorporated in a camera system developed by AIM in Heilbronn. A US company, OmniCorder Inc, uses the camera in the measurement standard system it has developed for diagnosing breast cancer. This system has just been approved by the US Food and Drug Administration and is now undergoing clinical tests.

The camera takes infrared pictures of the breast over several seconds. If cancer cells are present, it will modify blood circulation, which causes a slight rise in temperature and temperature variations.

After that, cancer specialists will be able to apply other established diagnostic techniques, said Peter Koidl, leader of the project in Freiburg. "It is a painless and fast technique for screening a lot of patients. It is much easier for patients to tolerate than other techniques."

The institute is part of the Fraunhofer Gesellschaft, a non-university research organisation specialising in applied research. The new, more sensitive detector will not be the end of the story. "We are working on improving the sensitivity," Koidl says. Other possible applications for the detector, such as thermal imaging and night vision, are being explored. "When we started work on the detector ten years ago, we were not specifically aiming at breast cancer detection. It was a happy coincidence."

Jennie Brookman