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Monte-Carlo simulations reveal that this increase in fluence can extend as far as 1.4mm into the skin. This means that the fluence applied at the skin surface will increase down to a depth of 1.4mm, then will drop rapidly due to absorption and scattering.
Relative fluence
7 55 nm
Ave rage d 1064nm 5 32 nm
2 50 2 40 2 30 2 20 2 10 2 00 1 90 1 80 1 70 1 60 1 50 1 40 1 30 1 20 1 10 1 00
90 80 70 60 50 40 30 20 10
Epidermis
Dermis
Fluence vs depth
Fluence applied at skin surface
1.5 1.8 2.1 2.4 2.7 3.0
Blood plexus 2%
0
0.085 Skin surface
Basal layer
Blood plexus 1%
0.3
0.6
Blood plexus 0.5%
0.9 1.2
Conclusion
Depth into the skin (mm)
Figure 4 – Change in fluence with depth for three wavelengths
The importance of back-scattering has been overlooked in laser/IPL skin treatments. Yet, it is clear from the above, that is it very important since it can have a significant effect on the fluences in the skin.
Understanding these processes will help to make proper choices about fluence settings, and, therefore, lead to better clinical results.
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