Page 96 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
Virtually all IPL systems also employ this method of using pulse trains – this is done to ‘protect’ the flashlamp from overheating. The difference is, though, many IPL systems allow the user to change the timings of these pulse trains, to a certain extent!
Long ’delay’ between pulses
Short ’delay’ between pulses
     Figure 55: The difference between ‘long’ and ‘short’ delays between sub-pulses is illustrated above. During ‘long’ delays the local temperature can fall significantly. However, if shorter ‘delays’ are utilised between sub- pulses, then the local temperatures can reach higher values.
Figure 55 shows clearly the difference in locally achieved temperatures in tissues when subjected to a sequence of pulses (a pulse train). Long delays between sub-pulses will allow some of the heat energy to conduct away (dissipate) from the absorbing sites, resulting in lower peak temperatures.
Clearly, the ideal situation is to reduce the ‘delays’ between sub-pulses to as low as possible – this will minimise the conduction of heat energy from the targets, and allow for higher temperatures to be achieved. With some systems, the individual energies of the sub-pulses may also be altered. We will discuss this in more detail in Chapter 3 and their consequences for clinical outcomes.
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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Tissue Temperature (C) Tissue Temperature (C)

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