U.K. engineers retool surveillance technology for medical applications

June 2, 2004

Temperature-sensitive body mapping has long held promise as a means for revealing vascular abnormalities, for example, around cancers or damaged muscle. Practical restraints, however, have caused the technology to fall short.Now a team from the

Temperature-sensitive body mapping has long held promise as a means for revealing vascular abnormalities, for example, around cancers or damaged muscle. Practical restraints, however, have caused the technology to fall short.

Now a team from the University of St. Andrews in Scotland believe they can break into the medical marketplace with a new kind of thermal imaging tool developed for military surveillance. Their Medical Imager for Sub-surface Temperature Mapping (MISTM) collects millimeter-wave radiation to build profiles of temperature just beneath the skin. The data, displayed as a digital color map, could find temperature hotspots characteristic of early-stage skin cancer or detect signs of vascular disease.

"Millimeter-wave imaging has generally been of interest for military applications, where you are looking for temperature signatures over a long range," said Dr. Duncan Robertson, research fellow at the University's Photonics Innovation Centre. "But what hadn't been considered was trying to focus that image down to a much smaller spot and get a higher resolution."

Conventional infrared imaging scarcely penetrates the skin at all, and its results are influenced by surface physiology, such as sweating. MISTM outclasses IR imaging, as well as microwave thermography, by mapping deeper into the tissue.

MISTM fares well in comparison with established medical imaging tools, as well. Unlike x-ray-based scanners, the new thermal imaging tool is passive, simply collecting a nonionizing form of electromagnetic radiation, allowing patients to undergo repeat scans at no risk. This opens up possible applications for imaging trauma victims or monitoring postoperative patients through clothes or dressings.

"If you wanted to see how a wound is healing, you wouldn't have to expose it, so this would minimize the chance of cross-infection," Robertson said.

The researchers have built a tabletop prototype capable of measuring temperatures to within six-tenths of a degree. This margin could be reduced further with advanced electronics, Robertson said. Functionality is controlled by a graphical user interface, which lets operators alter thermal mapping color scales, change temperature ranges, or review previous scans.

"It is really very easy to use. You can more or less pick up the technique in a matter of minutes just by experimenting," he said.

The imager is currently being studied at Ninewells Hospital in Dundee, U.K., home to one of the largest medical schools in Europe. Staff from the vascular laboratory of medical physics and from the hospital's dermatology department will each be collating data from healthy volunteers. These profiles of subcutaneous tissue temperature will provide an essential database of "normal" variations. Additional ethical approval will then be sought for clinical trials on patients with specific diseases.

"We have a list of potential conditions that might be of interest," Robertson said. "It may be that not all of them turn out to be relevant. But there could be one where this is a niche tool that lets you see things you simply can't with other techniques."

He acknowledges that the road from prototype to production line is going to be long. But the team is already investigating options for commercialization. The most likely route to market will be via a licensing agreement with an existing medical imaging vendor, though potential also exists for creating a spin-off company that makes the sensor head modules, Robertson said.

"Thermal imaging is still pretty much a research tool, and that makes it hard for us to assess the market," he said. "We are confident in the technology's abilities, and we are confident about what will be seen when the body is imaged at this wavelength. How that provides benefits to clinicians, however, only time will tell."