Back in 2016 (I think) I gave a talk to the American Society of Lasers Surgery and Medicine about the theory of Selective Photothermolysis. This is the theory which underpins all of today’s photothermal laser/IPL treatments. In this talk I discuss the idea behind thermal relaxation time and how it ‘fits’ with treatments. In fact,… Continue reading Selective Photothermolysis – an in-depth explanation
All hair follicles grow according to a cycle – ‘anagen, catagen, telogen’. The follicle germative cells promote anagen hair growth at consistently regular intervals resulting in periods of active growth, followed by inactivity. The duration of these periods depends on the which part of the body is being considered. I created a computer model to… Continue reading Laser/IPL Hair Removal – How many follicles do we kill each treatment?
Choosing the ‘best’ time between laser/IPL hair removal sessions is not simple. It depends on the hair growth cycles of the hairs we are targeting, which is not the same across the body. That means that we need to consider the body area when deciding how long to leave between sessions. We can only target… Continue reading More on the ‘best’ intervals between laser/IPL hair removal sessions…
I wrote a blog post back in September 2021 discussing my thoughts on the how to determine the optimum interval between laser/IPL hair sessions. It proved very popular amongst my readers. But, as soon as I posted it I began to doubt my own conclusions. Back then I suggested that we should wait for an… Continue reading ￼What is the ‘best’ interval between hair removal sessions (after treatment by lasers or IPLs)? Part 2.
These days we use a wide variety of lasers and IPLs to treat various targets in the skin. Two major targets are hair and blood vessels. But how much of the laser/IPL light is actually absorbed by these targets? Using data from two very clever scientists (Steve Jacques and Scott Prahl) it is relatively easy… Continue reading How strongly are different laser wavelengths absorbed in melanin and blood?
The other day I was training some very nice ladies and showed them a couple of photos of a tattoo I had treated with a Q-switched ruby laser. I realised, as I was talking to them, that this tattoo was the very first tattoo to be treated in our new, commercial clinic. Prior to this… Continue reading The world’s FIRST ever commercial laser tattoo patient…
Many laser and IPL treatments require a significant temperature rise in the target cells, to effectively kill them. We use light energy to induce this temperature rise. But, calculations show that, in some cases, less than 1% of the light energy is actually doing the job we want. That means that more than 99% of… Continue reading The ‘best’ way to cool the skin during laser/IPL treatments
I often hear laser/IPL operators saying that they “don’t want to burn their patients/clients.” They are wrong!! They DO want to ‘burn’ them, but in a very controlled manner… Every photothermal treatment (the removal of hair, blood vessels, benign pigmentation etc) requires delivering light energy to generate a thermal (heat) response in the tissues. We… Continue reading “I’ve burnt my patient!!” With IPL treatments, that is precisely what we are tying to do…
WARNING – This post is a bit more scientific than my usual stuff. BUT, it is worth persevering because you will (hopefully) understand more about your laser/IPL treatments, if you do… When we fire light energy at the skin, to treat hair, blood vessel, pigmentation etc, we know that some of the energy is absorbed… Continue reading How strongly do blood and melanin absorb light energy and how does this affect laser/IPL treatments?
How thick is a hair? Well, according to some research by physicist, Brian Ley (they do all the best research!!!), it ranges between 17 and 181 microns in diameter (see his results here). That is between 0.017 and 0.18 mm. So, that means that their cross-sectional areas [A = pi x (radius)2] are between 0.0000023 and 0.00026 square… Continue reading Thick and thin hair – how much light energy do they actually absorb during photothermal treatments?