Page 13 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Penetration Depth 100 Penetration Depth and Spot Size 102 Penetration Depth and Fluence 104 Fluence and Skin Cooling 108
Our Computer Models – What are the ‘optimum’ fluences? 109
The Importance of Back-scattering 112 How do fluence and pulsewidth relate to each other? 113 The relation between fluence, pulsewidth, temperature and cell damage 115 Just how important is pulsewidth? 118
Should we use longer pulses to reduce the pain in LHR? 123
Change in fluence with depth in the skin 125 Spot size 126 Where do the photons go in the skin? 126 The ‘Kill-Stun-Null’ Zones 130 Follicle sizes and TRTs 132 Conclusion 133
Laser Plume in the Air 134
Section 3.3 – The Importance of Proper Skin Cooling 136
Why is skin cooling so critical in photothermal treatments? 137
Pre- and post-cooling 138 “Over-cooling” the treatment area is virtually impossible!! 139 Success vs fluence 140 Ice vs air-cooling vs cryogens 143 Skin Cooling – The proper way to do it 145
Section 3.4 – Hair Growth Cycles & Timings 149
Introduction – The Hair Follicle 150
Hair Shaft and Follicle Sizes 151 Hair colour / thickness 153 The Hair Growth Cycle 154 Anagen – catagen – telogen timings 158 Hair Colours – Eumelanin and Pheomelanin 159 Visible Hairs – which phase are they in? 160 Heat transfer in the Hair Follicle – A Computer Model 161 How much hair is removed after each laser/IPL treatment? 164
Section 3.5 – How to Choose the Right Settings on Your Laser/IPL 166
The Clinical Endpoints 167
Clinical Endpoints 168
Threshold Denaturation Fluences – Four Devices 169
IPLs – Threshold fluences 169 Diode Laser – Threshold fluences 171 Long-pulsed Alexandrite Laser – Threshold fluences 172 Long-Pulsed Nd:YAG Laser – Threshold fluences 173 The instantaneous temperature in the hair shaft after irradiation 174
Increasing the fluence – what happens? 176
Our recommended starting fluences for different body sites 177 IPL ‘Over-heating’ – the need for proper surface cooling 178 What is the risk of burning the skin with a laser or IPL? 179 Threshold Fluences for Full Follicle Depths 182
________________________________________________________________________ 13 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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