▶ Previous Artlcle: #14-2. Long-pulsed Nd:YAG Laser
Extended theory of selective photothermolysis is an extended concept.
If the laser is irradiated for a longer time than the TRT of the target chromophore, thermal confinement does not occur in the target chromophore, but rather thermal diffusion occurs to the periphery, causing thermal damage to surrounding tissues to produce the targeted treatment outcomes (Figure 3).
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There are many things to consider when epilating with a long-pulsed Nd:YAG laser, but the most important is the patient’s skin condition.
If the skin color is dark, tanned, or pigmented, laser energy can be absorbed by the skin, not by the hair.
As a result, side effects such as burns, scars, depigmented nevi, and pigmentation may occur.
Therefore, it is recommended to reduce the pulse duration, spot size, and fluence and increase the amount of DCD (Dynamic Cooling Device), especially the pre-cooling amount, in cases where the skin color is dark or the epithelial layer is weakened due to aging.
Second, the condition of the hair should be considered. If the hair is thick, the pulse duration should be increased because the unit diameter is large.
Figure 3. Extended theory of selective photothermolysis.
-To be continued
