New insights into how lasers cut flesh( Lasers are at the cutting edge of su...)

Lasers are at the cutting edge of surgery.

From cosmetic to brain surgery, intense beams of coherent light are gradually replacing the steel scalpel for many procedures.

Despite this increasing popularity, there is still a lot that scientists do not know about the ways in which laser light interacts with living tissue. Now, some of these basic questions have been answered in the first investigation of how ultraviolet lasers similar to those used in LASIK eye surgery cut living tissues. It was published online in Physical Review Letters on October 10.

The effect that powerful lasers have on actual flesh varies both with the wavelength, or color, of the light and the duration of the pulses that they produce. The specific wavelengths of light that are absorbed by, reflected from or pass through different types of tissue can vary substantially. Therefore, different types of lasers work best in different medical procedures.

For lasers with pulse lengths of a millionth of a second or less, there are two basic cutting regimes:

• Mid-infrared lasers with long wavelengths cut by burning. That is, they heat up the tissue to the point where the chemical bonds holding it together break down. Because they automatically cauterize the cuts that they make, infrared lasers are used frequently for surgery in areas where there is a lot of bleeding.

• Shorter wavelength lasers in the near-infrared, visible and ultraviolet range cut by an entirely different mechanism. They create a series of micro-explosions that break the molecules apart. During each laser pulse, high-intensity light at the laser focus creates an electrically-charged gas known as a plasma. At the end of each laser pulse, the plasma collapses and the energy released produces the micro-explosions. As a result, these lasers particularly the ultraviolet ones can cut more precisely and produce less collateral damage than mid-infrared lasers. That is why they are being
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