Email is the second worst form of communicating and disseminating complex information. (The telepone is probably worse.)

As part of an email group I received a response to a question that was posed about how members of the list would like to receive information:

I am OK with a quick e-mail. I just don't have time to go to the web page frquently. It takes a few seconds to look at the e-mail subject line and delete if not interested.   M....

This reply got me thinking about why email does not work for sharing information among groups and what the remedies are. (see below)

Below is an exchange between a number of members. I've actually made it much more readable than the original by deleting all of the extra replies and leaving only the new message.

Please read the exchange below. I am talking about Density Setting with DeepFx and percent of area covered. I was taught that density 3 was 15% and density 4 is 20%. I routinely treat with Density 3. This expert saysthat density 3is really 70% and density 4 is really 100%and then he goes on to talk about Gausian Distribution and "Top Hat" Pulses. Can anyone help me with this. Does anyone understand what he is talking about? He won't tell me. He just tells me to read his text books on Laser Physics. My comments are in black, his are in blue. Thanks: I usually use density 3 which I thought was 15% coverage. NO, IT IS MORE LIKE 70% Dr. Ross uses Density 4 which I think is 20% IT IS REALLY ALMOST 100% REMEMBER, IT IS A GUASIAN DISTRIBUTION coverage. You say that anything over density 2, is doing a full resurfacing.CORRECT I thought a full resurfacing was 100%.AGAIN, REMEMBER THAT THESE ARE NOT "TOP HAT" PULSES OF ENERGY BUY ENERGY DELIVERED IN A GAUSIAN DISTRIBUTION. PLEASE REFER TO MY LASER TEXTBOOK OR ANY LASER TEXTBOOK FOR FURTHER EXPLAINATION I am confused here. Could you clarify?

______________

Those are the same questions I have. I am not sure if by 100% coverage he is adding the ablative area to the coagulation area which then is equal to 100% coverage. We need to remember that as we increase the depth we are also increasing the Lateral area of coagulation.
The next question then needs to be, what is the ideal area of ablation and the ideal area of coagulation?

_______________

I sent an email to my Lutronic rep (I bought the machine already) and asked him your question. Below is his answer. I had a demo of the Smartxide and asked how it compared as I couldn't begin to figure out their system of treatment. Below is what he said.

Hi. Yes they are discussing % of total coverage. The density on your eCO2 equates to Lumenis’ density #’s (1, 2, 3 or 4 apparently). We use spots per square centimeter (50-400) which is really the correct way to measure density. (I have been doing well with 100-150 spots/cm- Sandra's comment) When you set your energy and density (in static mode) there will be a smaller number displayed as a percent below the density, this is your percent of area coverage treated which is calculated by energy, pulse-width and amount of spots per area (density) for a known treatment area. In dynamic mode (where I blend) you must calculate the area yourself and input this so the machine can calculate the % coverage correctly for you (this is where the grid masks help).

In a fractional system the idea is to treat only a “fraction” of the skins surface thereby leaving a large percent untreated to help the treated skin heal more quickly. 20%-30% coverage is generally considered to be enough for a decent fractional treatment (more or less depending upon the condition of skin, downtime and outcome required).

When he discusses “Gaussian” & flat top beam profile most all CO2 lasers have this “Gaussian” output beam mode. It simple means there’s a bullet shaped output beam where there’s more energy in the center than the edges and a flat top beam has even energy distribution across the whole beam. I can’t understand how they can confuse a #2 density with a full face resurfacing though (20%-100%)... I would think you could see the difference... It would take you many passes (with the 120u tip) to have almost 100% coverage. Maybe their confusing their spot sizes. I could see their “Active” Fx with a 1.25mm spot achieving this much coverage. This would be similar to you using the 1000u tip. (This ablates the skin superficially, like a micropeel)

The SmartXide is unlike any other laser out there. It uses “pitch” and “dwell” (which measures distance between spots and pulse-width).

______________

Greg

He is talking about beam divergence. Basically the area the energy distributes away from the focal point (called beam waist). This is measured with complex equations calculated by half-angles (paraxial approximation).

In physics he is correct because if you use enough energy, the outer areas spread and can touch each other though weak.

For practical application purposes Jeff, your percentages are truncated for easier understanding. Meaning the most energy at the beam waist and the tissue effect there.

I could not pass this to everyone, would you please.

______________

I really think that the answer to this questionvaries depending onthe underlying wavelength used (Erbium vs CO2 vs 1500, etc) and the depth of the beam. For example, it would take more % coverage using Erbium to exert the 100% effect than from a CO2 because of the more rapid water evaporization effect by Erbium energy. The deeper the hole is drilled the more collateral heat dissipation there is. I believe it should take more than 30% coverage to get to the 100% effect with CO2. Why did I think so?? I made this deductive reasoning from the fact that the Fraxel REPAIR does "full ablative" effect with 40% coverage with 1.4 mm depth in a dynamic mode (optical scanning mode)

Kevin

______________

Jeff,
Regarding top hat and gaussian... when lasers hit an object they normally have a Gaussian curve which looks like a bell curve from the side. Looking down on it -it would appear as a target with changes in energy going out from the center-being most 'Hot" in the center and less hot going out. A top hat is usually obtained using optics to correct the curve to have an equal energy through out. Now instead of a bell curve it is a square looking like a you guessed it a top hat.
The guy does not know what he is talking about and is parroting information or he would have been happy to tell you about this. I would..it really turns me on. I believe what he iseludingto is that your energy level may not be homogenous across the beam. many operators will overlap the beam to account for this, but you then run the risk of too much fluence and burning someone. I am looking at this percent thing and wondering if they are nottalkingabout what we call pitch. Energy is generally described as Fluence which takes into account the wattage, the area and the time of exposure to beam--Fluence = (Power x Time)/ Area. Where a Joule (I'm Joulish) is a watt-secode thereby describing energy and time. (shut me up)
With my fractionated laser- we have pitch which, desribes how far apart the holes are. a low pitch like 15% would be less coverage than 70%. It describes the percent coverage of the skin surface.
:  The mathematical function that describes the Gaussian beam Check out this link for a cool flash movie about this. Sciton- my people- use optics to correct laser G-curve to a Top hat. www.tanitlazerepilasyon.com/images/beamshape.swf
Hope this helps. Bruce

______________

He is talking about beam divergence. Basically the area the energy distributes away from the focal point (called beam waist). This is measured with complex equations calculated by half-angles (paraxial approximation).

In physics he is correct because if you use enough energy, the outer areas spread and can touch each other though weak.

For practical application purposes Jeff, your percentages are truncated for easier understanding. Meaning the most energy at the beam waist and the tissue effect there.

I could not pass this to everyone, would you please.

Greg

The problems with disseminating information via email.

1. It's a discusssion that really only takes place between a few people. In the example above there are four or so people involved in the conversation. However, there are about 40 people that the email is being sent to.
2. It's difficult to follow. The way that threaded emails work places all sorts of convoluted text in the replies that has to be filtered.
3. It's insecure. Every person on the email can see the email address of every other person. Believe me, there are already technology companies on that mailing list (I"ve already been contacted about it) and every member is now identified. Don't think that's a problem? See Dermacare sue everyone on Medical Spa MD.
4. It invites spam. (See reason 3 above.) Once that list is sent out, it's beyond anyones control.
5. It's useless for anone not on the list. If the goal is to learn, email is about the worst way possible since each individual now has to manage the list themselves, wasting time.
6. It's not archived. On of the nice things about sites is that you can find past or relevant content by searching Medical Spa MD. With email, it's just gone.
7. It's unmanagable. With the list above there are multiple threads. Each has to be managed by me. With one it's a pain but doable. With three or more it's just a mess.

If you look at the list above you'll realize why there's been a move away from email and to managing content on the internet where content can more easily be managed and accessed.