What is fluence, and how is it calculated?

• A. The energy delivered per unit area; F = E/A, where E is energy per pulse (J) and A is spot size area (cm^2).
• B. The energy delivered per pulse divided by the treatment duration.
• C. The energy per unit volume of tissue.
• D. The wavelength of the laser.

Answer: (A)

Fluence is the energy delivered to tissue per unit area during a laser pulse. It tells you how concentrated the energy is on the treatment spot, which is crucial for achieving effective hair removal while staying within safe limits. It is calculated as F = E/A, where E is the energy per pulse (in joules) and A is the spot size area (in square centimeters). The result is in joules per square centimeter (J/cm^2). The other ideas don’t fit because dividing by treatment duration would give energy per area per time (not fluence); energy per unit volume would be energy density in tissue (J/cm^3); and wavelength is a property of the light, not how much energy is delivered per area.