Page 45 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Figure 14 – Uncontrolled skin cooling techniques
Cooling with cryo spray bursts are typically found on high end lasers (Alexandrite and Nd:YAG laser) for hair removal and vascular treatments while contact cooling with a window or waveguide is typically used with IPLs and diode lasers.
The cryo spray cooling has the advantage of providing the most aggressive epidermal cooling effect as it can cool the skin below 0oC. The disadvantage is that the cooling spot is larger than the spot size of the laser leading to some inconsistency when light pulses are delivered adjacent. The cyro spray can also create ice crystals on the skin if the humidity of the air high and this ice layer may block and reflect a substantial amount of the radiation before reaching into the skin. Research also indicates that the cooling effect with cryo sprays may only extend to a depth of around 0.2 mm – just below the epidermis.
The optimal skin cooling method is to use the light source waveguide in skin contact as heat sink. This method provides cooling exactly matching the size of spot and the cooling time can be fairly easily controlled. However, efficient skin contact cooling utilising the waveguide as heat sink can only achieved if the material of the waveguide is crystalline sapphire and that enough cooling power is provided to the waveguide for long-lasting treatment procedures.
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