Page 80 - An Introduction to Laser Tattoo Removal

Chapter 2 – Fundamentals of Laser Tattoo Removal v1.0
remove other greens! This all comes down to what is in the inks (watch an animation here)! We can never know this without a biopsy and a chemical analysis!!
It really depends on the constituents of the inks we are targeting.
Interestingly, PA’s Monte Carlo simulations found that these wavelengths back-scatter more than 532 or 1064nm. This was a surprising result, and unexpected. It means that much of the light energy we fire into the skin may be lost to the environment, purely due to scattering in the skin. The level of back-scattering increases as more ink is removed. Hence, towards the end of a patient’s treatment course, it becomes more difficult to remove the remaining chunks of ink, partly because of this back-scattering phenomenon.
Finally, the 1064nm wavelength – the fundamental line of the Nd:YAG laser. This wavelength has a number of advantages over the other three. It has the deepest penetration so can reach deeper ink aggregates. It has virtually zero absorption by both melanin and blood – so rarely causes problems with those chromophores. It is strongly absorbed by very dark colours such as black and dark blues.
The South Korean study (above) found that the picosecond 1064nm energy was the ‘best’ for black inks. This is not surprising since the absorption of energy by black ink at this wavelength is very high. However, as with 694 and 755nm, this wavelength is strongly back-scattered in the skin, thereby losing a lot of energy.
In addition to the high levels of back-scattering, we need to remember that good old-fashioned reflection also occurs with the titanium dioxide particles, of which there are many. In fact, it’s surprising that enough light energy remains in the skin to do the job in the first place...
An interesting conclusion by the South Korean researchers was that they thought that the wavelength choice was much more influential on clinical outcomes than the pulsewidth!
Watch an animation here to see how these wavelengths compare. Fluence
As you may recall from Chapter 1, the fluence is simply the energy density, or the ‘concentration’ of laser energy in a spot. It is defined as the applied energy divided by the spot size area and expressed a Joules/square centimetre (J/cm2).
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Chapter 2 LEVEL A Laser Tattoo Removal
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