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LASER DETERMINES SEVERITY OF BURNS

Researchers from the Biomedical Photonic Imaging department can use lasers to measure bloodflow within human tissue, and hence determine the severity of burn injuries. The special, super-fast camera they have developed takes a matter of seconds to do its work, rather than the several minutes of conventional techniques.

Each year, thousands of people in the Netherlands suffer serious burns. Many are children. It can be particularly difficult to assess the severity of skin damage in young patients. The conventional techniques require the patient to remain motionless for several minutes, which for a small child in pain is often asking too much.

In Twente, 'laser-doppler' techniques are now being used to assess the severity of burn injuries in a fraction of the time. Researchers have developed the TOPcam, a high-speed camera which uses slight variations in colour to detect the motion of particles in the blood. The TOPcam takes images at the rate of 25,000 frames a second to produce a film that shows the bloodflow through the skin.

Reflective red blood cells
The colour of light is determined by its wavelength. Laser light has a specific wavelength, and hence a specific colour. When it is directed onto a patient's body and meets the red blood cells within a blood vessel, the light is reflected at a slightly different wavelength, which means that the colour of the reflected light is also slightly different. The exact colour will depend on the number of red blood cells encountered.

The reflected light is detected by the TOPcam camera. Thousands of frames, all taken within seconds, are combined to form a bloodflow image. Several of these images can then be edited together to form a short video. The laser-doppler effect is used to determine the severity of burns: the greater the skin damage, the poorer circulation will be. The method also enables surgeons to ascertain whether a skin transplant has 'taken' and is getting the blood it needs to survive. If not, there is still time to try again.

A short video showing bloodflow as measured by laser. The more intense the red colour, the more blood there is. The patient's pulse rate can also be clearly seen.