Page 53 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Figure 17 - The pulsewidth and TRT as displayed in a temperature-time curve
We can clearly see in Figure 17 that the pulsewidth and TRT are not related in any way.
3. The denaturation time
The point in any photothermal treatment is to raise the temperature of some target cells or tissues and induce some kind of change in them. To achieve this, we must raise the temperature above the ‘denaturation threshold temperature’ – this is the temperature at which the proteins in the cells begin to ‘fall apart’, or, ‘denature’ (Figure 18).
This temperature is different for different proteins, due to their chemistry, but it is typically between 55 and 60C, in most cells.
Once the cells local temperature exceeds the threshold, they will begin to die, as long as the temperature is maintained for a sufficiently long period of time. If that time is too short, they may recover since they have not been sufficiently damaged (according to the Arrhenius Damage Equation).
We can see in Figure 18 that there exists a ‘denaturation zone’ when the temperature is above the denaturation threshold temperature. Cellular proteins will break down if they exist within this zone, i.e. if the temperature is high enough.
As the temperature climbs, the rate of denaturation also increases – exponentially.
________________________________________________________________________ 53 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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