In hair removal procedures, most long-pulsed Nd:YAG and Alexandrites lasers typically use short pulsewidths – usually less than 10ms, often less than 5ms. They can deliver all of their energy within these short pulses, whereas diode lasers and IPLs typically use longer pulses.
Such short pulses induce higher temperatures in the absorbing targets in the skin, since there is less time for the heat energy to diffuse away, during the delivery of the pulse.
Hence, an Nd:YAG laser delivering 10 Joules of energy in a 5ms pulse, will generate higher temperatures in a target than the same energy delivered by a diode laser or IPL in a 10 or 20 or 50ms pulse. In fact, the longer the pulse, the lower the peak (maximum) temperatures attained in the targets.
Most diodes and IPLs require longer pulses in order to deliver higher energies, compared with Alex and Nd:YAG lasers. This is simply a constraint of the technologies.
As a direct consequence, Alex and Nd:YAG lasers will inevitably induce more thermal damage, for the same fluence, compared with diodes and IPLs. Given that hair removal is a photothermal process, these higher temperatures result in ‘better’ clinical outcomes.
Poor Training
Another issue is the lack of proper training. Diode lasers and IPLs can generate the same clinical results as Alex and Nd:YAG lasers – if used correctly. Unfortunately, many users appear to be lacking some basic knowledge when applying their devices to the skin. Many are not taught about the importance or fluence or pulsewidth on the temperatures attained in the targets. Without understanding these important points, it is difficult to achieve good, consistent results.
Conclusion
Alex and Nd:YAG lasers are inherently ‘easier’ to use than diode lasers or IPLs, simply because of the shorter pulsewidths. However, longer pulsewidths can achieve the same results, but require more understanding of the photothermal processes.
Hope this helps,
Mike.
Mike Murphy's Blog 