New laser for surgeons

May 8 2007

Lasers have become a standard feature of surgical interventions, be it to alleviate the breathing difficulties of snorers or to treat prostate problems.

A new diode laser is ideally suited for use in soft tissue surgery. It has the advantage of being compact and inexpensive.

Snoring is not only inconvenient but also strenuous. The only solution for many sufferers is to undergo medical treatment that involves surgically removing part of the palate and the uvula. The instruments used to perform this operation often rely on a relatively cheap CO2 laser. But its light cannot be directed along a waveguide, and so an articulated arm has to be used to direct the beam to the correct position inside the patient’s mouth – not a very convenient way of working.

Researchers at the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Solid State Physics IAF in Freiburg have now developed a diode laser of a suitable wavelength that allows this problem to be overcome. “The laser output can be routed through a very fine light-conducting fiber,” says ILT project manager Dr. Konstantin Boucke. “Instead of laboriously positioning a mirror at the correct angle, the surgeon merely has to introduce a flexible optical fiber into the patient’s mouth.”

It is more economical, too: A typical diode laser costs less than a third of the price of other types of laser. What makes this particular diode laser so special is that it has a wavelength of two micrometers. “Light at this wavelength is readily absorbed by biological tissue, and the laser beam doesn’t penetrate far. Surgical incisions can be controlled much better with this laser. It can also be switched to a second operating mode in which it emits radiation at 800 to 980 nanometers, the ideal wavelength for arresting bleeding. This makes the new laser highly suitable for any type of soft tissue surgery – including prostate resection, which involves inserting an optical fiber in the urethra,” says Boucke. In order to produce a diode laser operating at this wavelength, the researchers had to work with an unconventional material – gallium antimonide – and adapt the optical setup accordingly. The cameras normally used to calibrate the laser beam were not sufficiently sensitive for a wavelength of two micrometers.

The new laser will also allow workpieces made of transparent plastic to be processed. A plastic material that appears transparent to the human eye allows conventional types of laser beam to pass through without obstruction, and without producing any melting effect. Until now, in order to weld transparent plastics with a laser, it was necessary to add colored pigments to the material, which added to the cost, changed the properties, and tainted the color of the resulting product. “The new laser permits transparent plastics to be joined without having to add pigments,” says Boucke. The prototype will be presented for the first time at the Laser trade show in Munich from June 18 to 21.

http://www.fraunhofer.de/