What is selective photothermolysis?
One of the benefits of laser treatment over other modalities of treatment (such as IPL) is the specificity of laser treatment. For example, to remove a brown spot in the skin, it may be possible to use liquid nitrogen to burn it off, however, by doing so, this will non-specifically affect the normal skin as well as the brown spot. Lasers are able to selectively treat the brown spot with minimal or no disruption to the normal skin. Lasers are able to specifically target a particular problem when the principles of selective photothermolysis are used.
Selective photothermolysis is the principle that allows lasers to be used to target a specific area/problem in the skin with minimal or no disruption to the surrounding normal skin. For selective photothermolysis to be successful, the following must occur (we will use the example of removing an unwanted blood vessel with laser to illustrate each point);
The laser wavelength must be highly attracted to the target e.g 532nm laser wavelength (as found on the Gemini laser) is targeted to haemoglobin which is present in blood vessels
The target must dissipate heat slower than the surrounding skin, and therefore accumulate heat from the laser e.g the blood vessel targeted by the 532nm wavelength will dissipate heat energy slower than the surround skin, therefore it accumulates heat and this causes it to shut down. The laser energy also must be applied to the target quickly enough for the target to heat up to a critical temperature.
The laser wavelength must reach the target e.g the 532nm wavelength needs to be able to penetrate down to the level of the capillary it is targeting.
If the above criteria are satisfied, it is then possible for laser to specifically target a particular problem in the skin, whether it be a freckle, capillary, or excess hair, without damage to the normal skin.