Article source: https://www.litonlaser.com/1064nm-laser-skin-beauty-application-case-discussion/
Regarding the skin application of 1064nm laser, recently, our training institution’s gold medal lecturer and several hospital attending doctors conducted a series of case discussions, including the skin characteristics and main functions of 1064nm laser, as well as the analysis of the principles of pigment treatment.
The following cases are provided by the community teacher of LITONLASER training institution, and the discussion opinions and suggestions are only for academic exchange.
1.Many doctors discussed the skin principles and applications of 1064nm laser.
Dr. Lou:
Teacher Hu mentioned two points (I felt it after watching Teacher Hu’s laser course).
First, the repair effect of 1064 on the skin barrier.
Second, the effect of 1064 on epidermal blasting for acne pits and epidermal spots.
As for the extended point, the photothermal effect of the 1064 handpiece is very low, almost no thermal damage, so the pigmentation rate is extremely low. It uses the light pressure effect of 1064. It may not be correct, but it is worth trying and learning.
Doctor Chen:
I have a question. If you use 1064 laser to blast and remove epidermal spots.
1. Raise the handpiece.
2. Do not raise the handpiece, directly adjust the spot size and increase the energy density (adjust the spot size and energy density to the same situation after raising the handpiece).
Is there any difference between the two?
Dr. Lou raised the handpiece by about 5cm according to this parameter. I simulated it on the machine in our institution. If it is raised like this, the actual spot size becomes 2mm, and the equivalent energy density is 6.25j/square centimeter. It is not in the defocused state, which is the state in the middle of the picture above. Then I directly adjusted the spot size to 2mm and the energy density to 6.5J/square centimeter, and hit the two black spots I drew with ink, and they were all crackling like firecrackers. The end point is the same. (Editor’s note: When the density is equal, the handpiece is raised and adjusted to the same spot size, and the reaction of the epidermis is basically the same.)
The focus of the 5mm spot is about 8.5cm in front of the handpiece. After the handpiece is raised, the spot shrinks relatively quickly. At this time, the energy density increases by a square number. If you are not skilled, you should try it with caution. For example, if the spot is reduced to 1mm, the energy density will be magnified by 25 times. The energy density of 1J/square centimeter will actually be equivalent to 25J/square centimeter. This is quite scary!
Regardless of whether the angle of incidence is larger or smaller, my understanding is that the depth of light action depends most on the physical properties of the wavelength of 1064nm itself. So I am very confused. No one told me the answer in the last discussion. For example, the focus of the 5mm spot is 8.5cm below the skin. At this time, 1064 can’t actually penetrate that deep.
Doctor Gao:
There is no absolute answer. Lasers can penetrate the human body, but the longer the wavelength, the slower it decays. Short wavelengths decay too quickly, and the energy is so low that it can be ignored when it reaches deep layers.
Common misunderstandings about laser action depth.
It is generally believed that: “The depth of laser action is determined by the wavelength and has little to do with energy and pulse width. When the energy is increased, the laser can reach deeper parts. Although the laser can be seen reaching deep tissues, the deep tissues have not changed.” This opinion is generally correct, but there is a considerable misunderstanding.
According to the Lambert-Beer law, the attenuation of light in an object is exponentially related to the transmittance of the material. In the same material, its attenuation coefficient is only related to the wavelength and is not affected by energy and pulse width. From this point of view alone, the statement in the first paragraph is completely correct.
Here, in order to express it more clearly, we can make the following assumptions: for a certain skin tissue, the intensity of Alex laser (Alex) will decay by half every time it transmits 1mm forward in the tissue; while the intensity of ruby laser (Ruby) will decay by half every time it transmits 2mm forward; the intensity of Nd:YAG laser will decay by half every time it transmits 4mm forward. When irradiating tissues, the above lasers are all set to a pulse width of 100ms and an energy density of 16J/cm2. In this way, the energy attenuation generated at different depths in the tissue is shown in Table 1.3.
Table 1.3 Changes in laser energy density at different depths within the skin
Depth
Alex(755nm)Ruby(694nm)Nd:YAG(1064nm)
Skin surface16 J/cm216 J/cm216 J/cm21mm depth8 J/cm22mm depth4 J/cm28 J/cm23mm depth2 J/cm24mm depth1 J/cm24 J/cm28 J/cm25mm depth0.5 J/cm26mm depth0.25 J/cm22 J/cm27mm depth0.125 J/cm28mm depth0.0625 J/cm21 J/cm24 J/cm2
This table lists the light energy density (J/cm’) of a single pulse. In fact, the Lambert-Beer law does not describe the energy density, but the intensity of light. Originally, the intensity of light should be expressed by power density (W/cm), but because the power density of a pulsed laser varies within a pulse, the average power density can only be calculated using the pulse width. For example, for a pulsed laser with a pulse width of 100ms and an energy density of 16J/cm, the average output power density is 16J/cm’-0.0001s=160000W/cm; if the pulse width is 10ms, the average output power density is 16J/cm-0.01s=1600W/cm; if a Q-switched laser with a pulse width of 100ns is used, the average output power density is 16J/cm’-0.0000001s=160000000W/cm. Then, if we follow this assumption, taking alexandrite laser as an example, its light intensity attenuation simulation is shown in Table 1.4.
Table 1.4 Changes in energy density inside the skin of lasers with the same wavelength
Depth
Alex(755nm)
100ms100μs100nsSkin surface160W/cm2160000W/cm2160000000W/cm21mm depth80W/cm280000W/cm280000000W/cm22mm depth40W/cm240000W/cm240000000W/cm23mm depth20W/cm220000W/cm220000000W/cm24mm depth10W/cm210000W/cm210000000W/cm25mm depth5W/cm25000W/cm25000000W/cm26mm depth2.5W/cm22500W/cm22500000W/cm27mm depth1.25W/cm21250W/cm21250000W/cm28mm depth0.625W/cm2625W/cm2625000W/cm29mm depth0.3125W/cm2312.5W/cm2312500W/cm210mm depth0.15625W/cm2156.25W/cm2156250W/cm211mm depth0.078125W/cm278.125W/cm278125W/cm212mm depth0.0390625W/cm239.0625W/cm239062.5W/cm2
Doctor Chen:
I raised this question last time. I hope Teacher Hong can give me some advice.
Hong Jun [LITONLASER]:
What’s the problem? Let me take a look and let’s talk about it together.
Doctor Chen:
I just mentioned that 1064nm laser is used to blast epidermal pigment spots. Either the handpiece is raised. Or the handpiece is not raised, and the light spot is directly adjusted to a smaller size to increase the energy density (the light spot and energy density are adjusted to the same situation after the handpiece is raised).
Is there any difference between the two? Raising the handpiece may cause a certain change in the laser injection angle, but no matter whether the injection angle is larger or smaller, my understanding is that the depth of light action is most important and depends on the physical properties of the 1064nm wavelength itself. So I am very confused.
Doctor Meng:
What you said is generally correct, but you overlooked a concept called “effective depth of action“. Professor Hong may be able to explain it more thoroughly. I will also wait for Professor Hong to explain it and see if my understanding is correct.
Hong Jun [LITONLASER]:
First, for lasers with full light output, not the form of microlenses, there is no difference in what you describe. This is determined by the basic characteristics of optics.
There is an indicator and prerequisite for the depth of incidence, which is that the light energy is attenuated and absorbed, leaving only 5%, and the upper skin tissue is non-invasive. Under this premise, the most important factor affecting the depth of incidence is the wavelength, but the longer it is, the deeper it is.
The second is the spot size, which is the problem caused by collision and scattering.
Therefore, under the same skin environment, these two indicators are important.
Third, it has to do with energy.
When the energy is appropriately increased, the penetration depth will be deepened. However, it must be subject to one condition, that is, the upper skin tissue cannot be burned or even vaporized by thermal degeneration.
In the picture you drew, Dr. Meng, the first two are normal. In the third picture, after the laser is defocused, due to the strong photon collision at the focus, although light has wave-particle duality, this collision will also significantly weaken the energy density and uniformity behind the focus.
After the laser enters the skin, it no longer shows pure focus because of the refraction and scattering of the turbid skin tissue, but the focus still exists.
Doctor Chen:
Teacher Hong, I have another question.
First: Regarding the ultra-picosecond machine of XX company (not convenient to disclose), does it output all light?
Second: 1064nm. 1. Without raising the handpiece, directly adjust to 2mm spot. 2. First adjust the spot to 5mm, and then reduce the spot to 2mm by raising the handpiece. In case 1 and 2, is the laser action depth the same? Is there a big difference?
Hong Jun [LITONLASER]:
Yes, full light. The depth is the same.
The prerequisite is that you have to adjust the energy density of the two to be the same.
Doctor Chen:
So, can I understand it this way?
In the future, when Dr. Lou uses 1064nm wavelength to blast epidermal pigment spots, he does not need to lower the energy and raise the handpiece. Instead, he can directly adjust the spot size to 2mm and increase the energy to more than 6J/cm, which will also produce the same epidermal spot blasting effect. Are the two the same in effect?
Doctor Meng:
I personally think the volume of damaged skin will be different?
Doctor Chen:
Does it mean that the damage to the normal tissues under the epidermal pigment spots is different? Is it getting bigger or smaller?
Doctor Meng:
To put it simply.
1. There are more tissues that are “beaten to death and cannot be revived”, and there are some tissues that are beaten half to death but can recover.
2. There are fewer tissues that are beaten to death, and more tissues that are “beaten half to death but can recover”.
I don’t know if this statement can express it clearly.
I tried to draw it, it may not be correct.
@Dr. Chen
This is my whole set of concepts, although the third one has some shortcomings. I didn’t express it clearly and didn’t use it well, but I firmly believe that the idea is fine. The previous usage can break through the energy limit given by the equipment, and the third one can break through the energy limit given by the machine to remove pigment spots, especially in the field of light adjustment.
Doctor Chen:
The reason I raised this question is actually very simple.
Is it really necessary to raise the handpiece so high?
Can raising the handpiece bring other benefits besides blasting epidermal pigment spots? (For example, reducing adverse reactions such as pigmentation).
If there are benefits, what is the theoretical basis for this benefit? In practical operation, raising the handpiece like this is actually quite dangerous and not conducive to recording parameters.
Sometimes, if it is raised by 0.5 cm, the energy density will double. If it is raised to the vicinity of the focus, the energy density is theoretically infinite.
Doctor Liu:
Whether it is necessary to raise the handpiece depends on the skin problem. For example, if you are preparing a plain scan with an energy density of 8mm and 1j, and suddenly find a few epidermal pigment spots or hyperplastic seborrheic keratosis and want to reach the treatment endpoint, you can instantly raise it to solve the problem without having to adjust the spot diameter and energy step by step.
Litonlaser:
I only know that President Lou raised the handpiece to reduce the risk of color sinking, reduce the photothermal effect, and reduce the photopressure effect.
Doctor Chen:
Occasionally, this method can be used to flexibly change the energy density without adjusting the parameters. This is something that all experienced doctors can do, but this is not the original intention of my question.
Doctor Meng:
@Dr. Chen I really tried my best to draw it, it may not be correct, but I will try to understand it.
The second type of laser is close to parallel light. As the energy decays, it is assumed that the energy decays to the point where it cannot “kill” cells after entering the skin 1mm. The damage depth is 1mm.
The first type, as the energy decays, theoretically it should not “kill” cells after entering the skin 1mm. However, the light converges in the middle. Maybe at 1.1mm, the cells at the center of the spot will still be “killed”, and the energy at 1.2mm from the center of the spot is still enough to “kill” cells.
Assuming that our basement membrane band is at 1.1mm, one of the two damages the basement membrane, and the other does not.
Doctor Chen:
What we mean is that it is not limited to treating acne scars, but also includes 1064nm laser treatment of epidermal spots such as freckles.
When 1064 is used to treat freckles, there should also be endpoint reactions such as slight frosting.
There are two ways to achieve endpoint reactions: 1. Adjust the light spot and continuously increase the energy. 2. Increase the light spot, preset a basic energy density, such as 1j, and then achieve a frosting reaction by raising the handpiece.
Some people believe that the second method can allow energy to be more concentrated at the focal position, more focused on the epidermal spots, so as to more accurately target the spots, reduce damage to deep tissues, and reduce pigmentation. The question is, is there really a difference between these two methods? Regarding penetration depth and collateral damage.
Doctor Lou:
Let me repeat that the 1064 hand lift does not use photothermal effects, but photopressure effects.
So what we should discuss is what is the photopressure effect?
Doctor Chen:
Then we need to discuss what is the photopressure effect?
In the usual laser treatment of pigmented diseases, what proportion of the effect is the photopressure effect?
With the same spot and energy density, how is the photopressure effect of the 1064nm laser enhanced after the handpiece is raised?
How much more is the proportion?
Doctor Kong:
The photo-pressure effect is also called the photoacoustic effect.
Litonlaser:
The light pressure effect is not photothermal or photochemical. When biological tissue is irradiated by laser, the pressure generated by photons hitting its surface is called light pressure.
It is generally believed that the lasers that form pressure are mainly pulse, Q-switched and mode-locked lasers. When ordinary light is irradiated to a biological body, the radiation pressure formed by photons hitting its surface is very small and can be ignored.
Although the light pressure of the laser (its own light pressure) is very low, its power is also enhanced to a certain extent when it is concentrated.
Light itself has light pressure. When a beam of light radiates to an object, photons collide on the surface of the object and can generate radiation pressure on the object. The energy density of laser is extremely high, and the influence of pressure generated by laser cannot be ignored.
Laser irradiation can generate two pressures: The pressure generated by the laser directly on the irradiated surface, that is, its own pressure, can reach 40g/cm2, which is quite objective.
The other is caused by thermal effect, called secondary pressure. This is because the laser divergence angle is very small, and the beam cross section can be focused to a small point by lens. When irradiating this point, the light energy is instantly converted into heat energy, which can cause the surface of the tissue to evaporate, expand, and even vaporize, thereby causing the pressure in the cells and tissues to rise sharply, causing micro explosions. The explosive material bursts out at a super-speed, generating a huge recoil force, and its destructive power is very serious.
Doctor Chen:
Then how does the light pressure change after 1064 lifts the machine handle?
Doctor Kong:
It gets bigger. You can think of it as mechanical impact. It focuses.
Dr. Cheng:
My understanding of this is that the dot pattern of picosecond laser is similar to ion beam.
Doctor Kong:
@Dr. Lou This refers to light pressure and secondary light pressure.
Doctor Chen:
From this point of view, the photopressure (photoacoustic) effect is more related to the pulse width.
Is it related to the distance after the handpiece is raised?
Doctor Lou:
What if the diameter of the spot becomes 0.5mm after the handpiece is raised?
And the range of the explosion may be 3mm.
Doctor Kong:
But what happens after you focus?
Doctor Chen:
I still can’t understand the relationship between the spot diameter becoming 0.5mm after the handpiece is raised and the blasting range of 3mm.
Doctor Kong:
It is like the intensity of the ultrasonic knife increases after it is focused. If you are very vertical, just vertical, for example, as you said just now, you keep the energy, and under the same total energy output, you can directly adjust it to a 2mm spot and a 5mm spot. Lift it up and lock the front into a 2mm light pulse. You feel that in theory, its light heat and light pressure should be the same. (Editor’s note: The density control is the same, the light heat and light pressure are basically the same when the handpiece is raised or not)
I haven’t tested this, but there is a problem. When you really adjust it to a 2mm spot, it is actually the lens inside, and its vertical movement is also a kind of movement. To put it bluntly, you are in front of this, whether it is 2mm or 5mm, their lenses are still away from the paper, such as the skin, and the distance is the same. (Editor’s note: The lens will move when the machine is adjusted, which is equivalent to artificially raising the handpiece).
In fact, in reality, when light is transmitted outside and inside the wall, there is definitely heat loss. I don’t know if this can be measured.
Doctor Lou:
I raise the handpiece not to reduce the spot size from 5 to 2, but to reduce the spot size to a dot, which is much smaller than 2mm. The explosion of a dot can lead to a 3mm change in the surrounding skin tissue.
Doctor Kong:
Also, whether you are vertical or not, whether it is vertical or off, this factor has an impact. When you lift the handpiece, can you really lift it to a 2mm spot? You may not lift it to 2mm, but you may lift it to a 3mm spot. It may not be able to accurately shoot two spots. The real spot, adjusted to the required spot, is the metal circle at the end of the light outlet. At the end, when you are vertical, this is the most standard. The size of the spot is adjusted to the size of the spot, but if you lift it with your hands or observe it with your eyes, it may not be lifted so standardly, so in this case, it may cause you to think it is accurate.
(Editor’s note: artificial lifting may not be able to accurately adjust to the required spot size, and without the assistance of the aiming frame, the light may not be vertical and the energy may be unstable).
In this imported device, the 2mm spot is the golden value. If the 2mm spot is used, the damage rate is still very low when using 532nm to treat freckles. However, the domestic ones are sometimes not standard. When the 2mm spot is adjusted, it may not be a 2mm spot. There is another problem. Have you noticed that when you adjust the 2mm spot, the energy on the skin is different, and the damage range is also different. For the same spot, the damage range of the high-energy spot is higher than that of the 2mm spot. If the energy is low, it is less. That’s it.
(Light pressure effect) One light pressure is one impact force. For example, this 2mm spot acts on 2mm skin. Its impact force is one light pressure. If you have the same energy, because the same energy also represents the same light pressure, then if the area you focus on is large, the pressure on the square centimeter will be smaller, but if you say that the spot is small, the pressure or impact force on the square centimeter will be stronger.
Doctor Chen:
Because this explanation is more convincing than other reasons.
It is focused, extremely high energy blasting. At this time, the energy density is far beyond the adjustment range that the machine interface can provide.
Why use 1064nm instead of CO2 laser? Because CO2 laser directly vaporizes. And 1064 has an extremely small spot, extremely high energy, and still blasts. Can I understand it this way? And the blasting of 1064 guarantees a certain penetration depth. 532nm cannot achieve it. CO2 laser cannot achieve it even more.
Doctor Kong:
The optimization of this spectrum depends mainly on what is being treated. Your depth and the spectrum you choose are related to the depth and absorption rate of the treatment. The higher the absorption rate, the shallower the depth. For freckles, the basal layer, in theory, 532 is definitely suitable, but 532 is very sensitive and not easy to control. In principle, it is not wrong to choose 532, but it is difficult to control during clinical operation. It is too sensitive and can be done if you are not careful.
For Ota nevus, this kind of dermal spot is relatively deep, it must be 1064, so 1064nm and 755nm are definitely suitable. When using 1064nm to treat Ota nevus, the spot should not be too large. If the spot is too large, you think it penetrates deeper, but in fact the damage is not enough. Or you reach the damage level, but the additional damage, that is, the negative damage, becomes larger. Many things are optimized, and the best performance is selected based on various factors.
There is nothing wrong with the wavelength of 532nm. What is its only problem? It is that it is too sensitive during the design of the machine and clinical application. If the manufacturer makes the low energy lower, 532nm is still very useful. Many manufacturers do not make the energy of 532nm so low, and start with high energy. The energy of 532nm should be set low, and the energy of 1064nm should be high. This is sometimes related to the design of the specific machine.
Doctor Chen:
I think Dr. Lou’s theory and practice can be used to guide 1064 treatment of acne pits and scars.
If you are treating epidermal spots, you should still follow the traditional light spot and energy density. There is no need to deliberately raise the hand. Raising the hand has nothing to do with color sinking. It has nothing to do with the depth of light action.
Doctor Meng:
Whether it is light heat or light pressure, we are trying to destroy something, the principle is the same.
If we use a focal spot, it is the so-called peeling method. Regardless of whether the local area is killed by the explosion or the water is vaporized, the result is that the local tissue “dies and scabs fall off”.
Doctor Kong:
You can think of the 1mm spot as the focus. When using a 2mm spot, it is not called a focus. In fact, it is a cone, which is a cone. For example, it can be considered as within 1mm, just a tip, which is the focus of the focus. Right?
So we are treating within the focus. When the light is transmitted in the skin, the light effect is scattered around. So we want to treat within the focus, that is, the direction of the light should be toward the center. In this way, the scattering of heat light to the surroundings in the skin can be reduced.
Why not use this outside the focus? The light entering the skin outside the focus is not only less, but also not focused. To put it bluntly, it is also the focus of light, which is to make it evenly output in the skin, and it will not be as diffuse as the surroundings.
Dr. Lou:
@ Doctor Chen You try to use 1064 to raise the hand and test the white paper.
Doctor Kong:
For this white paper, there is no need to consider the secondary light pressure, and the primary light pressure can almost be seen.
Doctor Chen:
I won’t do it anymore. My mind is full of extended thoughts and random thoughts:
1. The first effect of 1064nm laser focus piercing acne scars is still the photothermal effect, and then the secondary light pressure after the target color base is blasted. Which target color base plays the main role? How do each react? How much is the relationship with energy density? How much energy is converted into heat and transmitted to the surrounding tissue to cause thermal damage, and how much energy is converted into the mechanical force of light pressure. What is the principle of regeneration stimulation caused by the damage to the surrounding tissue caused by these mechanical forces?
2. Some manufacturers or researchers will measure the explosion area of 1064nm laser focus blasting, the range of light pressure damage area, and the stimulation of tissue regeneration through pathological sections, just like measuring the MTZ of carbon dioxide laser, so as to establish a reasonable laser point spacing, improve the 1064nm regeneration theory, etc.
2. Summary of the 1064nm laser discussion meeting.
This discussion mainly discussed the feasibility of 1064 in treating freckles and acne scars, and also introduced the concept of photopressure. Photopressure is small in life, but it cannot be ignored under high-power lasers! The doctors also expressed their opinions, from laser physics to machine analysis, as well as their own clinical experience, which also brought a new idea to colleagues! Looking forward to the follow-up feedback from doctors on this topic!
[The content of this article is for academic discussion only and is for medical professionals to read]
3. Learn about 1064nm laser machine.
For the application of 1064nm laser in the beauty industry, it tends to be more in hair removal and pigment treatment.
If 1064nm laser is added to the diode, it is used to remove darker hair such as black hair. For Q-switched ND:YAG laser or picosecond laser, it is more about melanin-related skin diseases.
The professional doctor discussion on the skin principle and efficacy of 1064nm laser shared in this article is more inclined to Q-switched laser. As a beauty machine manufacturer and beauty technology training institution, LITONLASER has its own Q-switched laser and the latest portable high-energy Q-switched tattoo removal machine.
We not only provide beauty machines at factory prices, but also provide every customer with professional beauty technology clinical data guides and online conference guidance on machine use.
If you want to know more about the machine details, please feel free to contact us: https://www.litonlaser.com/.
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