Page 82 - An Introduction to Laser Tattoo Removal

Chapter 2 – Fundamentals of Laser Tattoo Removal v1.0
Figure 37: Anisotropy can have a significant effect on the fluence in the skin
Hence, the 532nm may not be able to reach the deeper ink particles that the other wavelengths might reach. When choosing the most appropriate wavelengths for your tattoo ink colour, you must consider not only the absorption properties of that colour, but also its depth!
We should also think about ‘back-scattering’ as this can also have an important effect on treatments. Photons scatter as soon as they enter the skin. Many of them will change direction so many times that they leave the skin entirely, through the process called ‘back-scattering’. This occurs whether there is tattoo ink in the skin, or not.
PA constructed an 8-layer Monte Carlo model to investigate how much back-scattering might occur at different wavelengths.
Figure 38: Using the Monte Carlo computer modelling technique, PA calculated where the photons all end up. Many were found to have left the skin through the surface.
Inputting a large list of skin optical properties, he calculated where the photons finally ended up after their journey. He found that a significant proportion of them left the skin through the surface – much more than had been found before!
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Chapter 2 LEVEL A Laser Tattoo Removal
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