For the technicians on this board, when a machine is set to 40J - that means 40J of energy per squared cm, right? So it should be a constant energy density regardless of spot size, correct?
I’m a little concerned about this because I am considering have more LHR done, and am debating between the GentleLase and the LightSheer. The GentleLase that I got a test patch done with had a huge spot size - if I’m remembering correctly it was rectangular and about 3cm by 2cm (although I’ve been for a number of test patches with different systems, so I could be getting them mixed up. Is it possible there was a different lens fitted over the handpiece? This spot size seemed massive.)
Do some machines have (removable) handpiece attachments that would cause the output energy to be distributed over a larger spot size, thereby decreasing the energy density? I’m a big fan of larger spot sizes, but not at the price of underpowered treatment.
Also, are fluence levels comparable between different types of machine? (ie. is 40J from an Nd:YAG equivalent to a 40J setting on an IPL or a diode laser?) I suppose it would depend on whether this power rating is measured at the device output or at the light generator - and whether some machines would be more lossy than others. I’d guess it would also depend on operating frequency - the higher the frequency of the light emitted, the higher the power you need for the same depth penetration. Any info here?