The role of lasers in dermatology has increased dramatically over the past two decades. A fundamental understanding of laser-tissue interactions is vital for the proper and appropriate use in clinical practice.
1. Light can interact with tissue in four key ways:
- Transmission
- Reflection
- Scattering
- Absorption
2. Selective photothermolysis
- The theory of selective photothermolysis refers to laser energy absorption by a target chromophore without significant thermal damage to surrounding tissue.
- To achieve selective photothermolysis, 3 main factors:
- A. The laser must produce a beam of light with a wavelength preferentially absorbed by the chromophore in the lesion.
- B. The pulse duration of the laser beam must be shorter than the thermal relaxation time of the chromophore to prevent the spread of thermal energy beyond the targeted chromophore.
- C. The energy delivered to the site (fluence) must be high enough to destroy the chromophore within the pulse duration.
