Page 192 - Chapter 3 - Laser/IPL Hair Removal

So, keep cooling!
Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
SHR – How does it work?
The original study (Braun) which looked at the SHR technique applied a diode laser at the skin in relatively small areas – about 10 by 10cm squares. The laser emitted pulses at a relatively low fluence (5 to 10 J/cm2) in pulsewidths of 10 and 20ms, at 10 Hz (10 shots per second) and the laser head was scanned at the appropriate speed over the skin surface (around 10 cm/sec). This allowed for an evenly distributed series of laser pulses to heat both the dermis and hair follicles.
Royo et.al. also studied this technique. Most of their patients displayed “intense” erythema (reddening) and perifollicular oedema (swelling). They observed that, in 368 test subjects, they achieved a ‘good’ or ‘very good’ response in 289 of them, based on their own, subjective, evaluation.
However, it appears that this technique was severely altered in later years, by many manufacturers/suppliers. It has been sold as a ‘pain-free’ due to the relatively low fluences used. The problem arises when large areas are treated using this technique – the researchers point out that the dermis builds up heat during the treatment which raises its temperatures by a few degrees. This, coupled with the high temperatures in the follicles, leads to a good clinical outcome.
If larger areas are treated by this method, then the dermis may not attain the same temperatures as were found in the original study. The chances of success, therefore, drop significantly. We feel that many people applying the SHR technique are unaware that they are applying it incorrectly!
Discussions with many users across the planet reveal that more consistent results are easily achievable if the following criteria are adopted (with a diode laser):
Setting
Range
Fluence range (J/cm2)
5 – 30
Pulsewidth range (ms)
40 – 100
Frequency range (Hz)
3–7
Table 38 – Suitable ranges for the SHR technique
It appears that using a slightly ‘slower’ frequency, between 3 and 7 Hz, is easier to apply with more consistency. In addition, smaller areas should be treated, as used in the original study, rather than large areas like legs!
________________________________________________________________________ 192 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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