Page 214 - Mike Murphy's Blog Posts

Relative fluence
755nm 1064nm 532nm
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
0
0.085
0.6
Skin surface
Basal layer
Depth into the skin (mm)
Blood plexus 2%
Blood plexus 1%
0.3
Blood plexus 0.5%
0.9 1.2
Fluence applied at skin surface
1.5 1.8 2.1 2.4 2.7 3.0
Fluence vs depth
His model found that the back-scattering element (the photons heading back towards the skin surface) is hugely significant.
The graph above shows a red dotted line at the ‘100’ level. This represents the initial fluence fired into the skin. The three curves show, very clearly, that the fluence increases significantly just below the surface, down to the bottom of the basal layer. The amount of increase depends on the wavelength (which is not surprising).
What does this mean for treatments?
The maximum fluences are around 2.3, 2.0 and 1.5 times the initial fluences for the three wavelengths 755, 1064 and 532nm, respectively.
The red wavelengths (755 and 1064nm) remain above the initial fluence until a depth of around 1.5mm, whereas the 532nm drops below this level at a depth of around 0.4mm.
This has important ramifications of treatments, since most photothermal treatments are heavily dependent on the fluence.
Mike’s Blog Posts 214