here is a link to a computer based model of energy penetration depending on the spot size used : laser partner
from what i have read there it seems that 20j/cm^2 on 18mm spot size is less effective then 30j/cm^2 or 40j/cm^2 on 15/14mm spot size by 20-50% , and it is about the same energy as 20j/15mm …
also in all the researches i have read it seem that they all refering to 6 weeks intervals between each treatment , and this research talks about it specificaly : pubmed
another research, turns out you can have permanent hair reduction with 2 treatments at high fluence which means laser might effect all hair growth stages … alexandrite long term hair removal
sslhr hopefully can answer the settings questions in more detail. btw, on 15mm on GentleLASE, the max is 30 joules. for 40 joules, the next one down is 12mm, not 14.
the interval question has been around for a while, and the latest understand is that best interval is 8-12 weeks depending on the area because some areaa have longer cycles of growth and there wouldn’t be anything to treat at 6-8 weeks (face vs legs for example). and yes, the newer thinking is that hair can be killed in any stage given correct settings. basically, what we advise here and in FAQs is treating when you see new hair come in. everyone is different and you shouldn’t be following an arbitrary schedule anyways. there needs to be hair present in order for laser to affect it.
from this research it turns out that the 40j on 12mm is more effective in 50% then the 20j in 18mm … i just thought on posting this here because many people around here might be unaware to the settings and what is better like i am , so this can put on some light in the spot size are i guess,. sshlr , if you have anything to add or comment on this research it will be great.
about the hair growth i think you are right, but the question is will a treatment in the early anagen phase can give more result then treatment in the late anagen , which according to the newer thinking as you say doesnt really matter…
laser is attracted to pigment. when hair first appears, it is sometimes fine still and then becomes more coarse and dark. the anagen phase theory was borrowed from electrolysis, but it doesn’t really fit the way laser works. the more coarse the hair, the more attracted laser will be to the target, so with laser treatments, waiting until the hair is darker is beneficial (with electrolysis, it is easier to kill hair that is weaker, i.e. when hair first comes out).
it’s impossible to judge effectiveness of settings as a whole. it really depends on specific area you are treating, i.e. how deep the hair is on that area and how coarse the hair is, etc.
It’s a huge misunderstanding to believe ‘laser is attracted to pigment’. Laser isn’t attracted to anything. It goes about it’s path. That’s like saying car headlights are attracted to cat’s eyes, they’re not. Pigment absorbs whatever laser light is illuminated in it’s direction. The laser still irradiates all cells, organelles, DNA, rRNA, cell walls, Golgi Apparratus, microfiliments, whatever is in it’s path. These things are substance, they WILL be affected by the irradiation. It would be mistaken to think otherwise.
A good electrologist can kill hair completely in any stage. Fat hair is a good chance for a good #4 needle placement. Instant death, no burns.
hair removal lasers are made to target dark pigment. it passes through everything else that does not have pigment. plus, hair removal lasers do not emit any radiation that is harmful. with improper electrolysis treatments, it is possible to get burns where needle is inserted (that is how thermolysis works) and get scarring. and it is very hard to an average electrologist to kill hair that is not in anagen. that is why all the electrologists on this board continuously recommend to treat the hair as soon as it comes out.
If we are talking about energy density at the surface where it is calculated, what you are saying is correct. But if we are talking about the energy density at depth, then things are different and that is where spot size is important. And what the article you posted is all about. So 20 j at 15 mm is not the same at depth as 20 j at 18 mm. What matters in killing a hair is what happens at depth.
also in all the researches i have read it seem that they all refering to 6 weeks intervals between each treatment , and this research talks about it specificaly
I tend not to put too much stock into research done in a country like Iran with only 24 subjects in the study. Plus, not having read the study and what they were comparing, it is hard to make any sense of whether this was or was not a well designed and controlled study. Statistically it may be significant but empirically it may mean nothing.
another research, turns out you can have permanent hair reduction with 2 treatments at high fluence which means laser might effect all hair growth stages …
Actually you can have permanent hair reduction with just one treatment. A hair that is killed is permanently killed. It will never come back. But you really can’t get rid of all the hair with just two treatments.
You are right that laser is not attracted to pigment. Instead, laser energy is absorbed by pigment. So that part is correct.
The rest of the quote has some issues. First, let’s define the term “irradiation.”
Look it up. From wikkipedia.
Irradiation is the process by which an item is exposed to radiation. The exposure can be intentional, sometimes to serve a specific purpose, or it can be accidental. In common usage the term refers specifically to ionizing radiation, and to a level of radiation that will serve that specific purpose, rather than radiation exposure to normal levels of background radiation or abnormal levels of radiation due to accidental exposure.
The important point is that in common usage the term refers specifically to ionizing radiation. And that is critical.
There are lasers that use ionizing radiation. Ionizing radiation is generally radiation that has a wavelength of 380 nanometers (UV) or less. So when using ionizing radiation the effect on “cells, organelles, DNA, rRNA, cell walls, Golgi Apparratus, microfiliments, whatever is in it’s path” is important. And they will be affected.
But we are talking about laser hair removal. Laser hair removal in all it guises does not use ionizing radiation. And this non-ionizing radiation does not have an effect on structures that do not absorb the photonic energy.
So as far as laser hair removal is concerned “the cells, organelles, DNA, rRNA, cell walls, Golgi Apparratus, microfiliments, whatever is in it’s path” are not going to be affected. This is not to say that there isn’t an impact, but this impact is due to heat not to irradiation (as it is commonly used).
Lasers are made to exploit certain frequencies of light, and anything that is absorbed in that spectrum. A laser passing through tissue, cell plasma, and cell walls will somehow, someway effect these tissue components. There are far, far too many proteins, chemical bonds, fibrous connective tissues, and sub-cellular components to think otherwise. If what you say was the case, they could turn the laser up full strength and not worry about burns. If what you say is correct, which it is most definitely not, then the laser would pretty much pass right through the human body. But it doesn’t. That’s why people get big ugly burns from laser, because other tissues have absorbed the light energy and are roasting because of it. Actually, there is a very fine line between the power that can kill a hair, and the power that can make someone’s skin Original Recipe or Extra Crispy. And that’s because of light NOT passing ‘Rite-Thru’ a patient’s skin. And the term irradiation as a specific scientific meaning. You should become familiar with this term before you equate it with uranium, or equate uranium with irradiated chicken at your local Ralph’s (You do shop at Ralph’s?) And, it is much, much harder/impossible for a laser tech to kill a non-anagen hair than an electrologist. All one has to do is sink the needle painlessly a few millimeters deeper. It’s not hard at all! It’s not recommended, but it’s not that difficult. The papilla is bound to be down there at retraction depth. As for the laserologist, what can they do? The pigment thread has been seperated, there is not much of a chance at all to get high-photon energy to jump the gap.
First of all, you re-cap what is plain common sense. Then you say more common sense about irradiation which anybody with an MD should know cold, then you say it won’t impact subcellular components. This is so completely wrong that I just worry.
Why do you think laser hurts? Because it’s not impacting nerve endings?
Why do you think laser burns people? Becuase it’s not impacting the dermis?
I don’t understand what you mean by this. Can you clarify it?[/quote]
hope this will help clarify what i mean…
according to the calculations in the article:
"if the area of interest is at 4.5 mm depth and an 18 mm was compared to a 10 mm spot size (almost the same area as a 9x9 mm spot size). Assume 20 J/cm 2 was used for both spot sizes, the surface fluence for both lasers. At 4.5 mm the 10 mm will only get 67% of what the 18 mm is delivering. To deliver the same fluence at 4.5 mm the 10 mm spot would have to be increased to 30 J/cm 2 (20 J/cm 2 / 67% = 29.9 J/cm 2 ) "
“The increase needed with a 15 mm spot size would only be 1.7 J/cm 2 when compared to an 18 mm spot at a depth of 4.5 mm (20 / 97% = 21.7). Obviously the amount of energy delivered at all depths would be higher using a 15 mm spot 30 J/cm 2”
“with the GentleLASE ® Plus, a 12 mm spot would need to be used. While the 12 mm spot only delivers 78% of the energy of the 18 mm spot at a depth of 4.5 mm, at 40 J/cm 2 with the 12 mm spot, the total energy delivered to the hair bulb is 50% more than 20 J/cm 2 delivered with the 18 mm spot”
which means that it is not always true that higher spot size is alot better then smaller spot size as it is said here over and over again… and according to your expirience 5ms pulse width is more effective on normal hairs then 10ms ? in normal i mean not very fine hairs …
Again, we are in an argument because of your lack of knowledge. You make a statement that is wrong and inaccurate then you try to insult me because I point out your error.
I will answer a few of your questions but only because others are reading this post. I don’t expect you to concede anything.
All the effects of lasers at this wavelength are due to heat affects from absorption of photons by chromophores in the skin. Those chromophores are melanin, hemoglobin, and to a very limited extent, water. There is absolutely no absorption by subcellular components. The tissues the photons pass through do not absorb sufficient energy to create any real heat or to have any effect.
The difference between ionizing and non-ionizing radiation is strictly in the ability of radiation to ionize an atom or molecule. A short wavelength is required which is why anything longer than 380 nanometers is non-ionizing. I am not going to explain the physics of that. You can look it up. But hair removal lasers can not ionize nor affect submolecular particles. Nor can they affect DNA and those types or organelles. Their wavelength is just too long.
Why does laser hurt? And why does it burn? Strictly because enough photons are absorbed by the chromophores releasing enough heat energy. Again, you can look up the physics of that.
I take it you have never treated anyone with a laser. So you have never lasered anyone with very white skin and an area with no hair. Let me tell you what happens when you do that. You crank up the laser to say 50 joules (alex) and treat the area with no hair. Nothing happens. The client doesn’t feel anything (if they are very very pale). Until you move over to place where there are blood vessels or hair to absorb the energy, and then they feel it. They do not feel anything because there is nothing to absorb the photons. The photons are not impacting the nerve endings. And they don’t get burned because the photons are not impacting the dermis.
Where do the photons go. They go all over. They eventually get scattered and some do get absorbed because there is always a little pigment and/or blood around and some do come out the other side. Just like the light from a flashlight when shined on your hand.
A simple example I was shown once: Insert a black balloon into a white balloon. Blow up the black balloon, knot the two balloons together. Fire the laser at the balloons. The black balloon absorbs the heat and bursts inside the white balloon. White balloon completely unharmed.
Sslhr, it is yourself that will state a basic scientific fact, then attempt to draw some strange conclusion from that.
Once again, please try to be factual and grounded in common sense when you post.
A laser is not a flashlight.
your skin is much more complicated that a rubber ballon
Hemoglobin is absorbing the light energy, at least you got that somewhat right.
We all know about the different types of radiation. This is remedial. I’m glad you can understand that much.
You speak of photography and cameras. Someof the most famous photos in the world were snapped with kodak Instamatics, disposeables, and camera phones. The concept of importance and trained eye-view’s don’t always align. ‘Earthrise’ said to be the most important photo of the Twentieth Century, was taken by an astronaut that pointed the camera out the window and pressed a button, he had no training in that field.
I think what you need to realize is the harsh facts of your field of work; poeple attend two-day seminars and then they’re good to go. And that’s the reality my friend.
Mantaray
I’m sorry, I completely missed your post. Let me try to respond to it. The point you are making which is, according to the data presented in the model, at 4.5 mm 40j at 12 mm would be better than 20 j at 18. Let assume that there is no skin effect. Technically, you are correct based on the model.
So let’s talk about this model. First, Monte Carlo analysis is not really a modeling technique. It, instead is a way to do sensitivity analysis or multiple iterations of a mathematical model. It is a very good technique but it isn’t the model. And in this case we don’t know what the model actually is. No where do we see it. Furthermore, we don’t know what the sensitivity is to the underlying assumptions in the model, and there are many underlying assumptions. In other words, we don’t know how the model responds if you change some of the assumptions.
Some variables and models are very stable, which means that the results are the same over large changes in assumptions and other models are very sensitive. What that means is a small change in the assumptions will make a large change in the results. And unfortunately, we don’t know that.
What this model can tell us is that for a given set of assumptions and states, that a larger spot size will penetrate deeper into the dermis than a smaller spot size. The numbers in the table are an illustration of that concept.
What the model doesn’t tell us is how closely it really mimics reality. There is no question that larger spot size is more effective than smaller spot size. There is also no question that at shallower depths it really doesn’t matter as much (though it does in a different way). But what it doesn’t tell us is what the reality is at 4.5 mm depth. To use those numbers to predict how a 12 mm spot size behaves compared to a 20 mm spot size is a mistake because know one knows how accurate they are.
So your mathematical analysis is technically correct according to the data presented, but no really knows if it is correct according to reality. It may be, just that no one really knows. My sense is that at any spot size and wavelength there is a finite distance that effective energy can be delivered. Just how deep that is I don’t really know. But once you are past that distance, no amount of increase in power is going to do much as far as improving effectiveness. Past that distance a 100 joules with a 12 mm spot will not be as effective as a 18 mm spot at 20 joules. But what that distance is I don’t know.
Now back to the practical part of laser hair removal. 40 joules on a alexandrite is quite a pulse. There are not many people who can tolerate that. Where as 20 joules is quite tolerable. So regardless it is still better to be safe than sorry. So in most cases, especially when dealing with deeper hair, one is still much better off with the larger spot size. Not in every case but in the majority.
The rest of my comments are written to the people reading this thread. I am not concerned about what Mantaray thinks. He is not going to change his mind. As far as I know, he has never posted a comment in which he says anything positive about laser hair removal. I could be wrong, I haven’t read every post he has made. And I am happy to be corrected if someone will point out a post where he said something positive. (as opposed to negative or neutral) about laser hair removal. So the point is that he has an agenda and an obvious bias and that bias comes out on almost every post.
I could live with that, except that he says things that just aren’t true in his effort to promote electrolysis by putting down laser hair removal. Some of the things he says are true but they get lost among the untruth. And he is not intellectually honest enough to admit it. I think it is important to understand that when you read his posts.
If you read his comments back to me; rather than discussing this intellectually he tries to insult me with phrases like “at least you got that somewhat right” or “I’m glad you can understand that much.” Or what he does is misinterpret what I said.
For example, take his comment about cameras. I think the point he was trying to make is that I was wrong when I said that like photography, good laser hair removal requires the right equipment, experience, and training. Again this is his way of trying to point out that I am wrong. But here is what I actually wrote, isn’t it exactly what he says.
“Nowadays, almost everyone owns a camera. And for taking general snapshots those cameras are fine. And occasionally they can take a great picture.”
And my point is still correct. Earthrise may be the most important photo taken but it is more because of it’s context. A professional photographer, with professional equipment may have taken a better picture had they been in the same spot. But that doesn’t change the fact that good equipment, training, and experience is what is needed for good laser hair removal, just as it is for consistently excellent photographs.
So why do I care. Because laser hair removal has both positive and negative elements, just like electrolysis and everything else. What people need on this forum is honest advice and answers.
sslhr, we do appreciate your thoughtful responses and most of all, your knowledge. I think it’s clear to everyone reading any of these discussions who is biased and who is not. Unfortunately, some people won’t change their mind no matter how much evidence you present just because they don’t like admitting that they are wrong. It’s really too bad.
Interestingly enough, there were a couple posts last months where Mantaray actually admitted that someone experienced with an alexandrite laser can actually produce results. Don’t know what happened that week. Maybe it was due to a post here from male who had success with his treatments and posted asking questions about other areas he was considering now that he’s happy.
And you’re absolutely right! I did state that and will state it again. I honestly feel the GentleLase systems made by Candela are the workhorses of the LHR field. I feel the wavelength those lasers emit at are the most effective. I don’t think these units have near the absolute killing power of a decent electrology multiple-hit descending flash treatment, but would overwhelmingly rate these systems above the YAG’s and the Diodes.