Laser surgery: CO2or HF

Laser surgery may be improved by modifications based on similar processes in industrial applications. A major problem in materials processing is minimizing heat diffusion from the site of laser exposure. The same problem exists in the surgery of tissue with a CO2laser. A model based on vitreous surgery is described which indicates that radiation at 2.9 μm (HF laser) in short duration pulses, shorter than the thermal relaxation time (1.7 μs) of its 1μm thick absorption depth in water, will minimize thermal diffusion, and also take advantage of the large amount of heat removed by the phase change of water into steam. This model suggests that, for deep cuts, many pulses are preferable to a single long duration exposure, and that more delicate surgery may be possible with such short pulse, shallow absorption depth types of energy delivery. For coagulation (hemostasis control) as well as ablation, two simultaneous wavelengths are required: 2.9μm for cutting, and another with less absorption (such as Nd: YAG or argon lasers) for more penetration and heating of deeper layers and blood vessels. Among the secondary benefits of the use of the HF laser at 2.9μm is the ready availability of flexible optical fibers for a delivery system.