Efect of Laser Spot Size on Tissue Distribution of Light Energy

A beam of light incident on tissue may be:

• Refected

• Absorbed

• Scattered

Scattering in tissue broadens the incident beam, decreasing the efective fuence in the intended target area.For efective penetration, light needs to avoid scattering and surface absorption.Doubling the spot size will increase the efective volume by a factor of eight.A larger spot size usually enables faster and more efective treatment in dermatologic applications such as treatment of vascular lesions, laser hair removal, etc.However, more photons must be supplied by more complex and expensive power supplies, components, and delivery devices. As a general rule, doubling the spot size and halving the fuence will yield an equivalent efective fuence at a given depth. Tis efect becomes more pronounced with increasing depth.