History-I’ve been treating back/shoulders/up arms with apogee 9300 with last treatment at 25j/5ms/15 spot. 5 treatments with so so results. I am going to do 5 more but this setting above is the max for that laser.
I am considering a switch to a place which uses gentlelase and am double checking to see if I have my info correct. This laser is one you both have recommended in the past.
This is a better laser for me because-
1-Larger spot of 18 will penetrate deeper?
2-It can go to 20j/3ms/18 spot which will be more effective than 25j/5ms/15 spot on the apogee?
I would rather pay more and start treatment over with the gentlelase laser if it will be more effective than pay less and continue at the same settings on the apogee.
Any more recommendations, I will also spread treatments apart to minimum 3 months. One more thing, do you feel confident that spot size of 18 vs 15 will be the answer or is it the 3ms vs 5ms or is it the combo of 18 w/ 3ms vs 15 w/5ms. I realize there are no clear cut answers-what’s your opinion? Thank you.
I think switching to GentleLASE can help because you will be able to use 20 joules with 18mm to penetrate deeper, and if you will be using 15mm, you can go up as high as 30 joules, while still having 3ms, which is ultimately a higher setting that the Apogee is providing now. Hopefully, sslhr will weigh in here as well as he has experience with both lasers.
Quote: I will also spread treatments apart to minimum 3 months
Grumpy,
How come you spread the treatments so far apart. I thought it is best to go for a treatment between 6-10weeks after treatment. My laser centre tells me 4weeks however I think that is too close so I normally try and spread them exactly 9/10 weeks apart.
Mabye other people can comment what is too short and what is too long. We are talking about the back / shoulders and people who have already had a number of treatments.
for that area in particular, longer spacing is better because the hair cycle is longer. 10-16 weeks is probably best. lawrence, 6 weeks is way too early for almost every area. i would say treatments shouldn’t be less than 8 week apart in general.
You’ve touched on a point that is a little frustrating for me. I started January 2006 and have had 5 treatments that were spaced 8-9wks everytime. I did this because experts on this site said that would be optimal to catch hair in anagen/growth phase since after treatments the hair seem to start in again at approx 5-6 wk mark.
Now I did the 5 treatments, didn’t get that great of results, and now I’m being told that I need to spread the treatments longer. It seems that there is no exact/one size fits all treatment frequency. Different areas may vary as far as growth cycles etc.
I honestly don’t know what frequency to treat at so might as well give a longer span inbetween a try. It makes no sense to me to treat at longer frequencies as I would think the hair that has started to grow and is in anagen may fall out of its growth cycle before the next treatment…but since I don’t know for sure and it seems theories vary…what the hell.
the “treating hair in anagen” assumption was borrowed from electrolysis thinking and is what is being used by laser companies and others in the industry judging from their trials etc. sslhr was actually the one to bring the thought of spreading treatments longer on certain areas especially as he says he’s been experimenting and sometimes spreading out treatments longer works better. He said he himself is having treatments on his back once a year just as an experiment. Generally, he does say that most people want to get done with treatments sooner, so his clinics perform them at 8-12 weeks apart and it works well regardless. But in his opinion, certain areas can benefit from longer spacing. He can probably jump in here and explain his thinking to you himself, or you can look up his posts on that here and on the cosmetic enhancements forum. Generally, on the forums it is said that various areas benefit from different spacing, but it doesn’t vary that much. 8-12 weeks is usually safe. Face treatments usually need shorter periods due to hair cycles. So 8 weeks would be fine there. Back treatments would probably benefit from longer spacing, so closer to 12 weeks. But in either case, having treatments 8-9 weeks apart is not the cause of slow results for you.
I totally agree that my treatment frequency was not the major issue with my treatments thus far. It’s funny when I originally went to my laser place they wanted me to treat at 4-5 month intervals. Then I pushed them to treat me at the 8-10 wk mark. Now I’m being told to go back to the longer intervals. You can see where the frustration comes from.
I’m by no means trying to be a jerk or attack anyone’s advise. I am just trying to do the correct treatment whether it’s the laser type/frequency/or treatment settings. Posts can sound bitter at times which is not my intention, it stems from my confusion/frustration when trying to do what’s right. I do appreciate the help lagirl.
Hey grumpy, i wait like 3 months between sessions. I do this as it allows the hair to grow longer and as it grows longer, it also gets darker at the base. The coarser the hair is, the greater amount of heat gets to the base. Ive always heard on these forums that dark, coarse does gets better results. I think this is the main reason to wait longer.
i understand. the trouble in general is of course that these types of things are still being determined for a fact. the main issue is that it’s very hard to compare across various people to determine what works best as there are so many variables involved in each treatment.
Let me see if I can hop in here. First, regarding the difference between the two lasers. It really comes down to effective penetration at depth where the hair follicle lives rather than at the surface. There is a boundary cone (have to think 3D) where the scatter from the photons provide a steep drop off in temperature gradient no matter what the power setting. And the depth of that gradient is mostly a function of scatter. The setting that has the most impact on this is spot size. This may not make any sense because it is difficult to explain in words.
It is my belief based on empiric evidence and some understanding of physics that spot size is the critical component rather than power. Now that isn’t completely true, but between these two lasers the 18 mm spot is more important than the 25 joules. The difference between 5 ms and 3 ms is also important but not in this area.
What I have found is that a small percentage of people do not respond well to the Cynosure Apogee 9300 and will respond to the Candela Gentlelase, which tends to support my interpretation of what is going on. There is also some issues with coverage and overlap but the spot size is the big difference.
But I would bet money that your problem is that you were treated too quickly. For example, I have very good data on several backs that I followed very closely (mine being one of them). In almost all cases it took at least 3 months before any real hair started growing on them. My back is actually pretty hair free for about 4 months, with the last month being very fine hair. So having five treatments on a back in less than a year is way too quick by my thoughts. It doesn’t give your hair a chance to really grow back and provide the maximum target necessary to have the most effective treatment. In fact, if it was up to me, everyone would have treatments at least one year apart. But of course that isn’t practical nor would I want to wait that long if I were a regular customer. I’m like most people. I can spend months making a decision to buy something but once I make up my mind I want it yesterday. Telling people they are going to have to take 4 years to get rid of the hair is really not an easy sell. So we compromise at about 2-3 months. And for the most part, that works quite well. But backs do better a little longer.
I partially disagree on the 18mm spot size on the GentleLASE. I had to go to the GentleLASE after initially being treated with the Cynosure Apogee 6400. The reason is the power density is much higher on the GentleLASE due the the 3ms duration. The most effective setting for me on the GentleLASE is 26 joules on the 15mm spot size (power density = 8333.33 watts per square centimeter). 26 joule setting is not available on the 18mm spot. You may not realize it, but the power density rating is independent of the spot size. The total amount of watts delivered to the skin is dependant on the spot size. It is true spot size will allow you to cover more area and penetrate more skin, but the equipment has limitations. If I could have GentleLASE set to use 26 joules on the 18mm spot, that would be great.
Please help here, what is the rule of thumb on the diameter of the spot size and the penetration of the light? Is it one third of the spot size diameter?
As you and I both know, it is necessary to generate more power to cover a larger spot size of 18mm than the 15mm if you intend on using the same amount of joules. I believe the maximum setting on the GentleLASE for the 18mm spot size is 20 joules. Darn, I forgot what the max joules is on that. Well, the power density for that setting is 6666.67 watts per square centimeter for the 20 joule setting. That was much higher than the maximum setting my previous practitioner would use of 28joules per square centimeter on 5ms with a 12.5mm spot size on the Apogee 6400. The power density for that setting is only 5600 watts per square centimeter. But, taking into consideration the total amount of watts delivered per pulse is the watts per square centimeter multiplied by the area of the spot size. Doing the calculations, you can see the incremental decrease on the maximum joules for every increase in spot size. Laser units do not have an unlimited power supply, giving way to the limitations of the settings.
I’m glad you partially disagree with what I was saying about the 18 mm spot size. I’m going to be blunt. I don’t know what you are talking about in your comment.
So let’s start at the beginning. Tell me how you get from 26 joules at 15 mm spot size to 8333 watts per sq centimeter.
Just want to clarify a few facts. First, the 26 joules is really 26 joules Fluence.
1 joule Fluence = 1 joule/sq centimeter
1 Joule = 1 watt second.
watt is the actual power delivered by the laser. The Cynosure 9300 is a 90 watt laser. The Gentlelase is about the same wattage, but I don’t know the number off the top of my head. The Lightsheer diode is a 2,000 watt laser, but the wattage is measured differently in a diode laser compared to a pump chamber laser.
Let’s start here and we’ll get to the errors in your comments later.
First of all, I should correct myself on the Apogee laser. It is a 6200 not a 6400. Also, the GentleLASE’s maximum joule setting on the 18mm spot size is definitely 20 joules.
There are no errors in my values. This is how the value of Power Density or Irradiance is calculated. I use this value to convert settings from one laser to another with dissimilar pulse durations. Your values on watts are correct. But, are you taking into account the correct value of the duration of the pulse? There are equations used specifically for medical lasers which reference this value. Below is the basics on Power Density or Irradiance.
e = P/A
• e: irradiance (power density), W/cm²
• P: radiant power delivered, W
• A: area, cm²
I used the below formula for Power Density or Irradiance. You have to convert the milliseconds to seconds.
E = 20 J
t = 3 ms = 0.003 s
A = 1.0 cm²
e = (20 J)/[(1.0 cm²)(0.003 s)]
e = 6666.67 W/cm²
In reference to the Apogee 9300’s 90 watt laser, here is something to consider when that 90 watts of power is delivered in a different manner. For example, A CO2 laser delivers a 40 watt beam which is focused on a target 0.1 cm in diameter. The Power Density (Irradiance) is calculated below with some variations to the equation above. Here the Power Density value is more of a function of the area in which the laser is focused and not the duration of the pulse.
P = 40 W
d = 0.1 cm
A = (Pi)d²/4
e = P/A = (4P)/((Pi)d²)
e = (4)(40 W)/[(Pi)(0.1 cm)²]
e = 5090 W/cm²
The higher Power Density is what most likely makes the GentleLASE more effective than the Apogee, especially for the finer hair. I know it did for me. One practitioner used 20 joules on the 18mm spot size to treat my legs. There was absolutely no perifollicular adema.
P.S. Don’t get me wrong, the Apogee 6200 was a great laser to start off my treatments. But, the GentleLASE needs to be used to finish up the job.
I used the below formula for Power Density or Irradiance. You have to convert the milliseconds to seconds.
That is part of your problem. You are assuming a continous pulse laser when you try to convert a pulse that lasts 3 milliseconds or 5 milliseconds into a pulse of 1 second. So for example on the Cynosure 9300, I can generate a pulse that does 20 joules at 40 ms and then change it to a pulse that generates 20 joules at 5 ms. The absolute power is the same, but the peak power is higher. This is like saying, I am going to drive 30 miles and drive it in one hour or drive it in 30 minutes. Your velocity is different but your absolute distance driven is the same.
So the question is what is the value of peak power? Or a better way of saying it is what is the value of longer or shorter pulsewidth and this is really one of the thermal relaxation time of the target. I am not going to get into that at this point, but the real value of the different pulse widths has to do with the size of the hair and the concurrent risk to the skin.
But the bottom line is that the total amount of power remains the same regardless of the pulse width, assuming that the pulse width is less than a second.
So your numbers make no real sense and have no real value as far as laser hair removal. They are just numbers and wrong numbers to begin with. Let me give you some real numbers that you can put into your equations.
For a 20 joule pulse on a Gentlelase at 18 mm spot size at 1.5 hz.
The power is 20 joules/cm squared (it is calculated in joules fluence)
The spot size is 2.54 cm squared (don’t know where you got 1 cm squared).
Doing the correct equations, the actual joules are 50.8 joules per pulse. This converts to 50.8 watts per pulse and at 1.5 pulses per second this converts to 76.2 watt seconds.
Now this is the amount of actual energy delivered to the skin. Now I could convert the watts per pulse to peak power and state that at 3 milliseconds this would be equal to a 16,933 watt seconds (50.8/.003 seconds) continuous pulse laser. But again that is meaningless because only 50.8 watts of actual power was delivered to the skin.
Where you are wrong in all your calculations and where your numbers become meaningless is that you are basing all your calculations on the pulse and not taking into account the target and what happens in the target. In fact by your calculations if I took a laser pulse of 20 joules in a 10 mm spot size and a .0001 second pulsewidth (called a q switched laser and used for tattoos) I would get a peak power of 150,000 watts. What the heck does that mean?
But what happens in the target with a q switched laser is that the laser pulse actually sets up a shock wave due to the very short 100 millionth of a second pulse that breaks up the tattoo ink. The point is that pulse width is important but that power density as you are calculating it is meaningless for pulsed lasers.