Page 251 - Blog Posts v1

Conclusion
The original idea behind Anderson and Parrish's choice was to only damage the target without damaging the surrounding tissues - the basis of Selective Photothermolysis. While this works well in some cases it does not work very well in other targets, particularly larger targets.
In many cases the TRT is too short a time to allow sufficient denaturation to occur. This explains why IPL systems can be so useful when treating hair and blood vessels. They employ longer pulsewidths than most lasers, up to 100 ms in some systems. This is much longer than the TRTs of many target vessels/follicles.
It is curious that, in this age of widespread IPL usage, people still cling to the notion that the light energy must be delivered within one TRT. Cleary this is not true!
Additional note: Some people have spoken to me about 'long pulsed lasers' and asked if they are useful in such treatments. The problem with many of these so-called 'long pulsed' systems is that they utilise a train of short pulses within a long temporal envelope. Hence, the actual energy delivery occurs in short bursts with gaps between them. The critical timing here is the duration of those gaps. If they are too long then the overall temperature rise induced will be determined by how much time the laser energy is OFF, rather than ON!
I know, from measurements, that some lasers in use today have significant gaps between these short, individual pulses....
Cheers, Mike.
Mike’s Blog Posts 251