Page 138 - Mike Murphy's Blog Posts

Another issue is ‘anisotropy’ – this describes how scattering affects the laser light when it enters the skin (watch this video). It determines how deep the light can penetrate and how much is lost to back-scattering. Changing the wavelength is not trivial!!
Conclusion
The fact is, all wavelengths we use today for tattoo removal can treat all ink colours – but with a huge variation. Therefore, to improve results we must ‘lower’ the threshold fluences by changing wavelengths for certain colours (which is why we choose different lasers for different colours!).
However, as this analysis shows, it is patently not true that you can “only” treat some colours with a particular wavelength – it’s just ‘easier’ if we do! Or, in other words, those lasers require lower fluences than others.
If higher fluences are applied to all colours, they will react – but those fluences might be damaging to the surrounding tissues. Some other constituents of the skin will inevitably absorb some of the energy from these wavelengths too – particularly melanin and blood with the 532nm line, and melanin with both the ruby and alex lasers. That is the problem here...
So we need to aim for a balance – a sufficiently high fluence to damage the ink particles without excessive damage to the surrounding tissues.
Or..... a wholly new technique which does not involve light at all!!
Hope this helps, Mike.
Mike’s Blog Posts 138