Combined Fractional and Bulk Heating Modality for Nd:YAG Laser Skin Treatments

For deeply penetrating laser wavelengths, such as 1064 nm, the effect of light scattering in the skin leads to a spreading of the beam and consequently a significant reduction in effective fluence for small laser-beam spot sizes. For this reason, the 1064 nm Nd:YAG laser has not been used with fractional handpieces, where pixel beam spot sizes are typically very small. Instead, Nd:YAG fractional treatments are often performed using a special FRAC3, self-induced 3-D fractional effect. There are, however, certain Nd:YAG laser skin treatments, such as for resistant port wine stains and hemagiomas, that might benefit considerably by using a standard fractional beam technique. In this paper, we report on a recently introduced Nd:YAG laser scanner which operates at a fractional pixel size of 2 mm. Using a Monte Carlo numerical model, we show that this pixel size represents a suitable compromise between the effects of scattering and the desire to limit thermal effects to small pixel islands. We further show that scattering effects can be utilized to control the depth of the thermal fractional effect within the skin by varying the intra-spot pixel separation.