As the largest organ of human beings, skin plays a pivotal role in human life. In today's society, with the general improvement of material life, people's requirements for their own skin are not only free of pathological diseases. Environmental pollution, work force, bad habits, etc. have caused skin aging to come early, which has attracted people's attention and promoted the research on skin rejuvenation (especially face and neck). Different from the ablative skin reconstruction in the previous section, non-ablative skin reconstruction aims to heat the dermis mainly through thermodynamic effects under the premise of preserving the epidermis, induce the contraction, increase and structural changes of dermal collagen, reduce melanin in the epidermis and dermis, close and dilated capillaries, improve skin texture, and significantly improve the appearance and structure of light-aged skin. Although non-ablative skin reconstruction technology has not achieved the effect produced by ablative skin reconstruction technology, considering the advantages of the former such as less pain, shorter recovery time, lower cost, and fewer complications in the treatment area, more and more people favor this type of technology and it has been studied and developed by a large number of researchers.
Through the summary of the research of senior experts and scholars, this section will summarize and introduce the non-ablative face and neck rejuvenation technology, mainly focusing on infrared laser technology, visible light laser technology, visible light non-laser technology, radiofrequency technology, and photodynamic therapy.
(1) Long pulse Nd: YAG (1064nm) laser.
(2) Short pulse Q-switched Nd: YAG (1064nm) laser:
(3) Nd: YAG (1320nm) laser.
(4) 1450nm semiconductor laser.
(5) 1540nm erbium glass (Er:glass) laser.
(1) 585nm pulse dye laser
(2) 595nm pulse dye laser.
(1) Intense pulsed light (IPL).
(2) Broadband infrared light (TITAN)
(3) Light emitting diode (LED).
(1) Monopolar radiofrequency
(2) Bipolar radiofrequency
Infrared (wavelength 700nm~1mm) has good penetration into the skin and is divided into three parts: infrared A (wavelength 700-1400nm); infrared B (wavelength 1400~3000nm); infrared C (wavelength 3000nm~1mm). According to the infrared wavelength and color base absorption curve, the absorption rate of melanin and oxygenated hemoglobin decreases with the increase of wavelength. Only the absorption rate of water molecules to infrared is positively correlated with the wavelength. Through the absorption of infrared rays by water molecules (mainly), melanin and oxygenated hemoglobin in the dermis, photothermal effect or mechanical effect of light is generated, causing healable damage (thermal damage or mechanical damage) to the dermis tissue. The thermal damage temperature needs to be controlled at 60~70℃, and the collagen contraction temperature is controlled at 57~61℃. When the temperature exceeds the threshold, it may cause irreversible denaturation of collagen. These injuries activate the skin's self-repair mechanism, collagen self-repair, increase in new collagen, activation of fibroblasts and then increased expression of recruited extracellular matrix proteins. These series of short-term or long-term effects improve skin wrinkles and texture. 1. Long-pulse Nd:YAG (1064nm) laser Nd:YAG (1064nm) laser uses neodymium yttrium aluminum garnet as the medium (wavelength 1064nm). According to the infrared wavelength and color base absorption curve, the infrared at this wavelength is absorbed by water molecules, melanin and oxygenated hemoglobin. However, the absorption rate of these three targeted color bases to the infrared at this wavelength is relatively low, which makes the infrared at this wavelength have a deep penetration effect (optical penetration depth: 5~10mm), causing thermal damage to the skin and blood vessels under the skin. The thermal effect on the dermis is diffuse and can last for several seconds, which is also one of the reasons for the obvious erythema after treatment.
Research scholar Jiang Liya and others established a mouse experimental model, and used long-pulse Nd:YAG (1064nm) laser with pulse width of 3ms and 5ms and short-pulse Q-switched Nd:YAG (1064nm) laser with pulse width of 5ns to irradiate the back skin of mice after hair removal. The experimental design interval was 1 week, and the experiment was irradiated 4 times. Four test standards, including dermal collagen, skin elasticity, hydroxyproline content in the skin, and erythema reaction index after irradiation, were tested at different time points. According to the experimental results, there was no statistical significance between the two groups in the first three test standards, and in the erythema reaction index test standard, the long-pulse Nd:YAG (1064nm) laser was lower than the short-pulse Q-switched Nd:YAG (1064nm) laser. A large number of clinical experiments have found that long-pulse Nd:YAG (1064nm) laser has an advantage in improving skin elasticity.
2. Short-pulse Q-switched Nd:YAG (1064nm) laser is different from other non-ablative infrared laser technologies. After acting on tissues, it damages the tissues through mechanical effects to achieve the purpose of wrinkle removal. Point
Q-switched Nd:YAG (1064nm) laser has an extremely short pulse width, which is shorter than the thermal relaxation time of melanin particles. Although it has a pulse width of only nanoseconds, it has deep penetration and high peak power. The pigment particles in the epidermis and dermis explode instantly after being heated. Without damaging the surrounding normal tissues, the pigment cell framework is completely preserved, which accelerates the repair process.
Q-switched Nd:YAG (1064nm) laser can not only lighten spots, but also has a positive effect on collagen proliferation in the dermis. In 1997, Goldberg first used short-pulse Q-switched Nd:YAG (1064nm) laser for non-ablative skin rejuvenation, with an energy density of 5.5J/cm2, a spot of 3mm, and a pulse width of 40ns. He then tried to use low energy density 2.5J/cm?, spot 7mm, pulse width 6~20ns to treat fine facial wrinkles. By comparing the patient's appearance and microscopic histological examination, high energy density parameters may better stimulate collagen proliferation. Due to the advantages of this laser, such as accurate effect, less side effects, and high safety performance, it has made outstanding contributions in the field of non-ablative facial rejuvenation.
3. Nd:YAG (1320nm) laser The principle of the laser's action on the skin is still thermal damage. The absorption rate of this wavelength laser by water is lower than that of other infrared lasers with water as the target color base. Unlike the wavelength 1064nm target color base, this wavelength is not affected by melanin and oxygenated hemoglobin absorption, which makes this wavelength laser have the strongest penetration into the dermis, reaching a depth of 500um~2mm. Collagen is thermally damaged by heat, which shortens and regenerates. According to clinical and histological studies by some researchers, the short-term use of Nd:YAG (1320nm) laser to promote skin rejuvenation may involve other factors besides collagen self-repair due to heat, but no clear textual explanation has been given. Classic parameters: energy density 15~30J/cm'; pulse width 30~50ms. Early instruments did not have cooling equipment. At that time, the parameters used by scholars were: energy density 32J/cm?; spot 5mm. Later, thermal sensors and cooling equipment were added to this instrument to control the epidermal temperature at 42~48℃, and the corresponding parameters were: energy density 28~40J/cm'; spot 5nm. The complications (blister and erythema reaction) of the previous instrument are lighter. The latest instrument is the CoolTouch3 laser transmission instrument produced by CooTouch in California, USA. Spray coolant is given before (10ms), during (5~10ms), and after (10ms) the pulse, respectively. The energy density is 13~15J/cm?; the pulse duration is fixed at 50ms. The effect of Nd:YAG (1320nm) laser on collagen tissue is different from that of short-pulse Q-switched d:YAG (1064nm) laser on collagen tissue. Nd:YAG (1320nm) laser forms a thermal effect on collagen in the dermis, promoting the proliferation of type III collagen. Short-pulse Q-switched Nd:YAG (1064nm) laser causes the proliferation of type III collagen in the dermis through mechanical effects. Compared with the latter, Nd:YAG (1320nm) laser damages the dermis structure more lightly, and has a more prominent effect on non-dynamic (static) wrinkles. 4.1450nm semiconductor laser The wavelength of 1450nm laser belongs to the infrared B (wavelength 1400~3 000nm) category. The absorption rate of water molecules is higher than that of Nd:YAG (1320nm) laser, and the deepest penetration depth reaches 500mm in the dermis. This also leads to more obvious pain, edema and erythema reactions during treatment than Nd:YAG (1320nm) laser. The main ones used in clinical practice are low-power semiconductor instruments (Smoothbeam) with cooling systems. The energy density is not uniform, and there are 8~24J/cm', 10~20J/cm, 12~16J/cm; the spot is 4~6mm; the upper limit of the pulse width is 250ms.
Preliminary clinical experiments have shown that most scholars believe that this laser does not significantly improve wrinkles, but can have some effect on fine wrinkles. Some experts believe that it is significantly effective in improving wrinkles, and patients have good self-satisfaction.
5.1540nm Erbium glass (Er:glass) laser This wavelength laser targets only water molecules. The main mechanism of action is thermal damage repair. It can penetrate 0.4~2.0mm dermis. Some scholars mentioned that the subepidermal depth of 0.10.4mm dermis is the best thermal effect zone for improving wrinkles. Compared with this effective depth, the 1540nm Erbium glass (Er:glass) laser penetrates deeper and may be accompanied by scars.
Reference parameters: energy density 20~30J/cm’; pulse width 10~100ms; spot 4mm. These parameters also have some problems in clinical application, such as long pulse duration, small spot, contact cooling method is not easy to control, etc.
Clinical experimental research shows that this laser has a slight improvement effect on fine lines on the face (periorbital and perioral, etc.) and can reduce the depth of wrinkles, but because the wavelength laser penetration is more effective in improving the depth of wrinkles, and the cooling system is not accurately controlled, it can cause adverse reactions such as erythema reaction, pigmentation and scars.
With the development of research, lasers with a wavelength of 500~600nm have also been used for non-ablative wrinkle removal. Unlike infrared lasers (invisible lasers), this type of laser is represented by 585nm and 595nm pulse dye lasers, which can penetrate the skin about 400pm. According to the wavelength and color base absorption curve, it can be concluded that oxygenated hemoglobin has an absorption peak at about 580mm. After the capillaries in the dermis absorb the laser, thermal damage is caused, which starts a series of inflammatory reactions (such as reversible damage to vascular endothelial cells, infiltration of neutrophils, mast cells, monocytes, etc. outside the blood vessels) and self-repair mechanisms (such as the release of multiple cell growth factors, etc.), promoting collagen fiber proliferation (new collagen fibers and elastic fibers, increased expression of type [collagen and type III collagen), and smoothing wrinkles.
1.585nm pulse dye laser This laser targets the capillaries in the dermis. After the vascular endothelial cells of the capillaries are heated, the self-repair process begins, and the number of collagen fibers increases. Classic parameters: energy density 2-3Jcm'; pulse duration 350ps; spot size 5mm. Although higher energy density can also increase the content of dermal collagen and extracellular matrix proteins, the probability of complications such as edema and purpura in patients after treatment increases.
In the past decade, 585nm pulse dye laser has been used for vascular diseases such as port wine stains, with considerable efficacy and few scars in the treatment area. In recent years, this laser has been used for facial rejuvenation treatment. After one treatment, nearly half of the 20 volunteers were satisfied with their facial wrinkles. Regular biopsy after treatment showed an increase in dermal collagen.
2. The working principle of 595nm pulse dye laser is basically similar to that of 585nm pulse dye laser, but the treatment parameters of 595nm pulse dye laser are slightly adjusted from the former, with energy density of 6~8J/cm; pulse duration of 1.5~40ms; spot size of 10mm. The above is visible light laser technology, which is slightly different from the infrared laser technology in the previous section in the biology, including biological physics and biological chemistry, produced in skin rejuvenation treatment. Some researchers have established an animal model to compare the biological effects of Nd:YAG (1320nm) laser and 595nm pulse dye laser on the skin, and used collagen proliferation ability and skin water retention ability as test standards. It is concluded that Nd:YAG (1320nm) laser has better skin water retention ability than 595nm pulse dye laser, and 595nm pulse dye laser is better in collagen regeneration.
1. Intense pulsed light (IPL) In the existing field of skin rejuvenation, intense pulsed light exists as a common light different from laser, and has emerged in this field. Intense pulsed light is first of all an incoherent ordinary light, which has poor selectivity compared to laser. It is a wide-spectrum light (wavelength of 500~1200nm) formed by a high-intensity light source (such as a lamp) first focusing through a focusing lens and then filtering out the shorter wavelength light through a filter. The wavelength of intense pulsed light can be adjusted manually, the pulse width can be adjusted continuously, and both single pulse and multi-pulse can be used. It has a large spot. When treating the skin, it can be directly contacted or treated with gel. The reaction after treatment is relatively mild compared to laser. The emitted photons carry enough energy to penetrate the human skin. The epidermis absorbs a small part of the energy. The pigment particles and hemoglobin in the dermis convert the remaining part of the energy into heat energy, producing a photothermal effect, which decomposes and absorbs the targeted tissue. Collagen shortens after heating and self-repairs and regenerates after thermal damage. The activity and number of fibroblasts are enhanced, the expression levels of type I collagen and type III collagen are increased, and the elastic fibers are arranged more closely, making the skin firm and tender. Appropriate pulse width and pulse delay time can achieve the treatment purpose under the premise of protecting the epidermis.
Different filters are used to filter different wavelengths of light to treat different skin problems. In clinical practice, filters 515nm/550nm/560nm/590nm are used to treat capillary dilation, and the effect is better than Nd:YAG laser, and similar to pulsed dye laser (PDL). Filters 510nm/550nm are used to treat port wine stains, but the effect is not as obvious as pulse dye laser. Filters 560nm/590nm/615nm/640nm/695nm can treat hemangiomas, but are rarely used clinically. Filters 550~640nm are effective for Asian freckles. Filters 560nm/590nm/615nm are almost perfect for the treatment of epidermal melasma. Filters 550nm/570nm/590nm try to treat post-symptomatic pigmentation. Filters 550~640nm can be used clinically for hair removal.
The first generation of intense pulsed light treatment system (PhotodermLV) was developed in 1990, first put into clinical use in 1994, and approved for use by the US FDA in 1995. The light waves output by the PhotoderlVPL treatment system are bell-shaped waves with uneven energy; after more than ten years of development, the second generation (Vasculigh) and the third generation (Quan In 2003, Lumenis launched the fourth-generation multifunctional beauty platform, LumenisOne, in which the IPL module provides single, double and triple pulse treatment modes, with energy density of 3~90]/cm' and pulse delay of 2~100ms. At present, BBLTM combines laser with IPL treatment system. Due to its advanced cooling system, the treatment process is more comfortable and easier to be accepted by people. Palomar and DDD of Denmark use double-filtered intense pulsed light (I2PL) in clinical practice, filtering out both low-wavelength and high-wavelength parts of the spectrum.
We list and introduce the treatment of skin aging with intense pulsed light (i.e. type II skin rejuvenation) separately. Due to personal genetic genes and external factors, skin aging is manifested as: rough and thickened skin, sagging skin, skin pigmentation, capillary dilation, wrinkles, etc. In the process of studying skin rejuvenation, intense pulsed light has an irreplaceable position. Its effect on skin rejuvenation is not as good as pulse dye laser, and it is not as good as fractional laser, radio frequency technology, etc. in treating wrinkles and sagging skin. However, due to its non-invasiveness, single treatment can improve comprehensive skin problems, and no downtime, intense pulsed light is still the first-line choice in skin rejuvenation treatment (except for people with Fizpatick V skin type and V skin type).
The selection of treatment parameters needs to consider factors such as disease type, skin type, and skin thickness. Different wavelengths are used according to the different absorption peaks of hemoglobin (large absorption peak at 417nm, small absorption peak at 542nm and 577nm), reduced hemoglobin (430nm, 555nm), melanin (280~1200nm absorption peak), etc., and of course the choice of wavelength is also affected by Filzpatrick skin type and the thickness and depth of the lesion skin. For example, if the skin color is dark and the skin thickness is thick, a longer wavelength filter needs to be used. The pulse width needs to be less than or equal to the thermal relaxation time of the target tissue. When the energy is constant, the pulse width is inversely proportional to tissue damage. In clinical practice, the treatment mode is often double pulse or triple pulse, which releases energy in batches to reduce damage to tissues. According to the analysis of clinical case data, taking the middle-aged female facial skin photoaging of Fizpalzick III skin type as an example, a 590nm/640nm filter, double pulse or triple pulse treatment mode, pulse width of 5ms/6ms, pulse delay time of 35ms, energy density controlled at 15-18J/em. 4-6 times for a course of treatment, the interval time is 3~4 weeks.
2. Light-emitting diode (LED) Light-emitting diode is a kind of emitter that can emit infrared-visible ultraviolet light. LEDs of different materials emit light of different wavelengths (such as gallium arsenide for infrared spectrum, gallium arsenide for green light, gallium nitride for blue light, etc.), which can emit low-intensity light and can generate strong energy light in integrated arrays.
The mechanism of LED action is mainly light regulation mechanism, including at the mitochondrial level and at the receptor level. The targeted chromophore for mitochondrial absorption of photon energy exists on the mitochondrial cell membrane and is a cytochrome molecule (synthesized by the proto-phyrin region), namely cytochrome oxidase. After the antennae molecules on the mitochondrial membrane absorb photon energy, the structure changes, which increases the amount of adenosine triphosphate (ATP) and enhances cell activity. It increases cell gene expression at the receptor level and amplifies or weakens cell signal transduction. Appropriate treatment parameters and wavelengths determine the activation of cell activity and collagen proliferation. Although LED has only been developed in the field of skin rejuvenation for a short time, it is still favored by researchers because of its many advantages, such as small size, rapid response, easy operation, selectable bands, long service life, high luminous efficiency, safety and painlessness, non-vaporization, and no downtime.
Clinically, LED emission wavelength 590nm yellow light is used for the treatment of facial photoaging, with an energy density of 0.1J/, and 8 treatments are performed with an interval of 4 weeks. Appearance and histological evaluations were performed 6 and 12 months after treatment, and it was found that the skin texture was improved, erythema and pigmentation were reduced, wrinkles were reduced, and histological findings showed that the content of dermal papillary layer collagen was significantly increased. Some researchers have also combined LED with other lasers (such as infrared laser, intense pulsed light, radio frequency, etc.), and found that LED can enhance the photothermal effect of these lasers. In recent years, with the study of photodynamics, [ED emission wavelength of 633nm red light is combined with photodynamics, and the photosensitizer is 5-aminolevulinic acid (5-ALA) at a concentration of 5%, 10%, and 20%, so as to achieve the effect of beauty and skin rejuvenation.
At present, due to the constraints of high-standard LED development technology and the lack of detection standards, LED has not been widely promoted for clinical use. These limiting factors have put LED technology in a bottleneck period. With the development of technology, LED will play a very important role in the medical field in the future.
3. Broadband infrared light technology (Near-infrared, NIR) Recently, a skin tightening technology powered by wide-spectrum infrared light has been launched in the field of skin rejuvenation. Among them, the Tilan technology produced and designed by Cutema in Brisbane, California, USA, can produce an infrared light source system with a wavelength of 1100~1800nm. Israel's Alma company has also launched an infrared light source device that can produce a wavelength of 900-1600nm. The following uses Tilan technology as an example to introduce the clinical application of broadband infrared technology (NIR).
The infrared light with a wavelength of 1100~1800nm generated by Tilan technology uses water as the target color base. The water molecules in the skin and the collagen layer in the dermis fully absorb the infrared light within this wavelength range, so that the tissue is evenly heated. It can also skip the epidermis and directly heat the dermis to shrink and proliferate collagen. The penetration depth is greater than that of non-ablative lasers, but less than that of radio frequency technology. The heating depth is 1~3mm below the epidermis. Different from the mode of action of radio frequency, the treatment of Tin technology aims at continuous heating of the deep layer of the skin, and the low energy density acts on the skin for a long time, which makes the treatment process painless, and even does not require surface anesthesia below a certain energy density (30J/em). In order to shrink and proliferate collagen, radio frequency technology uses extremely short pulses with high-intensity energy for instantaneous action. According to the collagen contraction description formula, it can be inferred that the amount of collagen contraction can be determined by both temperature and action time. For example, if the temperature is 5℃ lower, the action time needs to be increased by 10 times to maintain the original amount of collagen fiber contraction. When the dermis is heated above 50℃, collagen begins to shrink immediately, which is generally controlled at 57~61℃. Collagen will undergo irreversible denaturation above the upper limit temperature. The above explains why broadband infrared light technology with lower energy density can also produce immediate and subsequent shrinkage effects. The treatment time of each part of Tian technology is controlled at 4-11s, and the skin is heated for a sufficient time. The skin shrinks immediately after treatment. Then the thermal damage starts the self-repair process, which causes the regeneration of extracellular matrix in the skin, collagen and elastin regeneration within a period of time. These effects combine to make the skin continue to shrink and tighten for a period of time. Titan technology has a sapphire cooling system before, during and after treatment to ensure that the epidermal temperature is within a safe range below 40℃. It can be used to tighten the skin of the whole body, improve skin texture, and make the skin delicate, smooth and firm. The treatment parameters are set according to different plans for different parts (for example, the energy density used for facial treatment is generally lower than the energy density used for abdominal treatment). Energy density (flux) = total energy of the entire infrared light pulse/area of the affected skin, controlled at 28~46J/cm2. The energy density needs to be lowered for bony surfaces and sensitive areas. The number of repetitions in the treatment area is more than that in the general area. The number of repetitions in the skin anchor points and pinning lines is more than that in the general area. 2-3 times is a course, with an interval of about 30 days. Conventional ice compresses are generally not required after treatment with Tin technology, unless sensitive patients can be given ice cubes to cool the treatment area. If local erythema occurs, it will disappear in 24~48 hours. Compared with general laser technology, photon technology, and radio frequency technology, Tia technology is safer and easier for patients to accept.
Radio frequency (RF) technology is a facial rejuvenation treatment method different from laser technology and photon technology. It is a high-frequency electromagnetic wave that can be radiated and transmitted over long distances in space. The so-called high frequency is between 100kHz and 30GHz. To ensure that the frequency of electromagnetic waves that can be transmitted in space must be higher than 100kHz, and radio waves below this frequency can be absorbed by the surface. Radio frequency technology has actually been deeply integrated into our daily life and work. Mobile phones, televisions, radio stations, microwave ovens, etc. are inseparable from radio frequency technology. As early as the 18th century, people had applied electric current to the medical field, such as cardiac defibrillation; in 1897, Nagelschmidt and others used electric current to treat joint and vascular diseases, and named this therapy "diathermy"; in the early 20th century, Simon Pozzi and others used electrocautery to treat skin cancer; then Doyen improved electrocautery to electrocoagulation. Until now, these two technologies are still used in clinical practice. In 1995, Thermage Company of the United States launched Thermatool technology. The following year, SolhMedical Company invented Themmage (Thermage) monopolar radio frequency technology. After passing the US FDA certification in 2002, the diathermy principle of radio frequency technology has been widely used in skin tightening treatment.
The biological effect of radio frequency technology on dermis and subcutaneous tissue is still a thermal effect, which is different from the thermal effect of laser and photon. The energy of laser and photon is absorbed by the target color group in the tissue and converted into heat energy to heat the tissue to produce reversible thermal damage. The principle of radio frequency thermal penetration is to place the biological tissue between the electrodes in the created electric field. The current with a frequency of up to 1-40.68MHz/s causes the polarity of the tissue charged in the electric field to convert at the same frequency. There is natural positive impedance in the biological tissue (the natural electrical impedance of different tissues is different), which makes the bipolar water molecules in the tissue rotate or vibrate rapidly. The charge in the biological tissue under the condition of monopolar electrode changes from positive to negative, causing the polarized molecules to rotate and move to generate resistance, which is then converted into heat energy. The heating depth can reach 15~20mm. The current flow area of the tissue under the condition of bipolar electrode is smaller, and the heat penetration is shallower than that of monopolar. The depth and intensity of the thermal effect of radiofrequency technology can be determined by factors such as the treatment electrode (monopolar, bipolar, multipolar, etc.), the frequency of the current, the energy released, the action time, and the conductivity of the tissue. The larger the range of the treatment electrode current loop, the deeper the thermal effect and the stronger the effect; the higher the current frequency, the shallower the thermal penetration depth: the released energy is controlled by the current intensity (1), the natural impedance of biological tissue (R) and the action time (T), among which the current intensity is the dominant factor: sufficient action time can produce effective thermal damage: the natural electrical impedance of different tissues is different, such as fat impedance> skin impedance> muscle impedance. The above factors directly affect the skin tightening effect and whether complications occur. The thermal effect changes the collagen in the dermis and the fibers of the subdermal tissue. Collagen is a triple helix structure composed of bonds connecting each chain. The thermal effect makes the triple helix structure unstable. After the helix structure is untied, the collagen shrinks, producing the immediate effect of radiofrequency. Within weeks or even months after treatment, the body's thermal injury repair mechanism is activated, the expression of type II collagen mRNA is significantly upregulated, and the new collagen increases: the heat generated by the long-term effect of enhanced radiotherapy can also closely attach the skin to the fascia fibers deep in the face, achieving the effect of skin tightening and lifting. It is precisely because of the non-selective photothermal effect of the radiofrequency action principle that it has broadened the way for the treatment of people of color, and the depth of radiofrequency action is deeper than that of laser, intense pulsed light, broadband infrared light, etc. (it can reach the subcutaneous fat layer).
According to the action principle of radiofrequency technology, researchers have fully developed radiofrequency technology in clinical work. It is mainly reflected in the following aspects.
1. Slow down skin aging, including improving wrinkles, lifting sagging skin, brightening skin tone (ELOS technology), etc. Mainly including frown lines, crow's feet, forehead lines, nasal lines, perioral lines, neck wrinkles, stretch marks, sagging skin in other parts of the body, etc.
2. Improve skin orange peel-like changes. Skin orange peel-like changes often occur in the thighs and buttocks of middle-aged women, showing uneven skin and face, and special small depressions caused by the traction of the attachment points. Radio frequency promotes collagen regeneration, promotes lymphatic circulation, accelerates the decomposition of fat cells, and improves the appearance of orange peel.
3. Local shaping and weight loss, such as postpartum abdominal repair and skin tightening after liposuction.
4. Hair removal for patients with dark skin Using the principle of non-pigment-dependent thermal effect of radio frequency, combining radio frequency technology with intense pulsed light or laser technology for hair removal treatment can reduce or avoid adverse reactions such as epidermal burns caused by dark skin color.
5. Repair scars. The thermal effect can loosen scars and rearrange new collagen fibers, thereby achieving the effect of repairing scars.
6. Other applications include telangiectasia, active acne, onychomycosis, psoriasis, etc. During radiofrequency treatment, the selection of the treatment area is very important, that is, the skin anchor point is determined by evaluating the range of skin activity. Before introducing the anchor point, we will briefly explain the direction of collagen contraction. Radiofrequency can uniformly heat a specific layer of skin, causing collagen fibers to shorten and contract. The direction of skin contraction may follow the direction of collagen fiber arrangement; the arrangement of collagen in the dermis is not parallel and orderly like in connective tissues such as tendons. They are randomly arranged, which means that the direction of contraction is more likely to be centripetal, and because there is interaction between each treatment point, it is difficult to predict the contraction axis. According to the principle of "anticipated contraction dynamics", determining the skin anchor point and treating the anchor area is better than full-face treatment, and the adjacent carrier tissue is lifted by contraction of the anchor point. Push the skin (hairline and in front of the ear) with your thumb. The junction between the immovable and movable points after the skin is pushed is the anchor point, which is connected to form a treatment line. These are the key areas for treatment. The eyebrow lifting treatment area is generally the inner upper forehead or the outer side of the temporal region; the lower eyelid ptosis treatment area is the cheek or the two zygomatic bone areas; the cheek lifting and nasolabial fold improvement should focus on the preauricular area as the main treatment area; the neck lifting should be in the area above the thyroid cartilage level (except for patients with early cervical muscle bands, the mastoid area and the posterior and lateral side of the hairline should be selected).
During the treatment process, the patient's awareness of pain cannot be ignored. The heat sensation gradually increases and accumulates. If the patient complains of obvious unbearable pain sensation, the treatment should be stopped immediately. Preoperative surface anesthesia can relieve the pain caused by treatment. Studies have shown that 4% compound lidocaine gel (LMX-4) is easier to remove than 5% compound lidocaine gel (LMX-5), reducing the adverse effects of treatment such as burns caused by changes in local impedance due to residual surface anesthetics. The surface anesthetic should be applied to the treatment area for 1~1.5h. Energy parameters are set according to individual responses. For example, the Thermacool device produced and designed by Thermage in California, USA, uses low energy density and multiple scans, which is the most classic and effective. Clinical studies have shown that high energy scanning is not ideal and increases the risk of side effects (such as lipoatrophy).
The radiofrequency can not directly act on the wrinkles, and it is easy to form a "tissue paper" effect or a "sausage" effect. Generally, 12.5 is set as the initial energy, and it is adjusted according to the pain reported by the patient. Patients with obvious pain can adjust the energy to 11.5 or even 10.5. The number of scans varies according to the different parts. Areas with more fat (such as cheeks, etc.) need to be scanned 5 to 6 times, while other parts can be scanned 2-4 times. Of course, the number of scans also needs to be combined with the patient's own feelings of pain.
Radiofrequency treatment has many obvious advantages, but there are also the possibility of complications, which is closely related to the operator's operation process and the setting of energy parameters. Epidermal burns are the most common complication. Improper use of the mixture and failure to replace the treatment head can lead to such complications. When burns occur, patients often complain of severe pain, also known as "match pain". At this time, ice compressing the treatment area immediately is the key. Fat atrophy in the treatment area is the most serious complication, which is mostly related to excessive energy. After this complication occurs, it can only be corrected by using fillers. Very few patients may experience conscious numbness in the treatment area, which is self-limiting.
Radio frequency instruments are generally composed of a host, a transmitter, and a receiver, which can be divided into monopolar, bipolar, and multipolar radio frequency. Monopolar radio frequency equipment consists of a transmitter, a cooling regulator, and a treatment head. The surface of the treatment head is covered with an insulating film. Human skin is used as a semiconductor. The treatment head is the transmitter of the monopolar radio frequency, and the receiver is another conductive plate connected. The bipolar radio frequency treatment head itself is equipped with a transmitter and a receiver, and the current forms a path between the two electrodes. The distance between the monopolar radio frequency transmitter and the receiver is far, and the electromagnetic field formed is large, so the heating area is relatively large, and the heating depth can reach 15~20mm, so it has obvious advantages in tightening and lifting the skin of the face, neck, waist, abdomen, limbs, and thighs. The bipolar radiofrequency treatment handpiece contains both the transmitter and the receiver. The distance between the two electrodes is short, and the effective energy penetration depth is only half of the distance between the electrodes, which limits the heat penetration depth. In addition, the bipolar radiofrequency energy conduction exists between the two electrodes in the form of concentric circles or strips arranged in parallel. These characteristics make bipolar radiofrequency mainly used in areas with thin skin or fine wrinkles such as around the eyes and lips, ensuring the safety of the treatment area. With the development of technology, in order to increase the therapeutic effect of bipolar radiofrequency and ensure the safety of the treatment area, some combined technologies have emerged, combining light energy (IPL/LED), radiofrequency (bipolar), surface precooling (contact cooling system) or negative pressure suction, namely electro-optical synergy technology (ELOS), which reduces the resistance of the treatment area while protecting the epidermis, increases the penetration depth and radiofrequency selectivity, and reduces the energy used for radiofrequency and light. The use of negative pressure technology can accelerate fat decomposition and tissue metabolism, and achieve the therapeutic effect of sculpting the body. Some treatment platforms that combine monopolar radiofrequency with bipolar radiofrequency are also included. They can improve personalized problems in different parts by adjusting the treatment mode, such as the Accent Navigator radiofrequency system produced in Israel.
Photodynamic therapy (PDT), also known as photochemical therapy (PCT), is composed of three main elements: photosensitizer, light, and oxygen. Photosensitizers are injected into the human body or applied locally to the human body. The drug can be selectively enriched in active cells. When a light source (laser and non-laser) of a certain wavelength is irradiated to the medication site, biochemical reactions and molecular effects occur. A large amount of active oxygen species (ROS) is produced through type I reactions, and singlet oxygen is produced through type II reactions. These oxides attack target cells and destroy and kill them. Due to their instability, the action time is short, so they cannot damage surrounding normal tissues. This technology can be used for both fluorescence diagnosis and disease treatment.
In the early 20th century, people initially tried photodynamic therapy. In 1960, blood derivatives (HD) were used for early diagnosis and treatment of tumors. In the 1970s and 1980s, photodynamic therapy with blood derivatives as the main photosensitizer pushed its treatment of tumors to a climax. In 1990, my country began to use HPD-PDT to treat non-tumor diseases such as port wine stains. In 1998, my country officially approved the use of HPD for the treatment of tumors. In the 1990s, the United States used the photosensitizer 20% 5-aminolevulinic acid (ALA) for the treatment of photokeratosis. In 2000, Bitter et al. first reported the clinical application of photodynamic therapy in the field of skin rejuvenation. In 2013, Karrers et al. pointed out at a consensus conference that using different light sources (intense pulsed light, light-emitting diodes and lasers) to irradiate photoaged skin with different photosensitizers (5-aminolevulinic acid, etc.) can achieve gratifying results. The selection of photosensitizers should follow the principle of low toxicity, strong penetration, excitation by visible light that can penetrate tissues, and the generation of singlet oxygen or triplet reactive oxygen after excitation. At present, the most commonly used photosensitizers are widely present in nature and contain tetrapyrrole aromatic ring structures, mainly hematoporphyrin, etc. There is also the possibility of using second-class (crxaporphyrin, etc.) and third-class (halogenated nitrogen anthracenes and quinones, etc.) photosensitizers. The first-generation photosensitizers have poor stability, are prone to cause skin phototoxic reactions and require a long time to avoid light. The second-generation photosensitizers are often used clinically. In the field of skin rejuvenation, the most commonly used photosensitizer is 20% 5-aminolevulinic acid (ALA), and the effect of local medication is better than intravenous or oral administration. Some researchers have also used ALA esters (5-aminolevulinic acid methyl ester, MAL) in clinical research and made comparisons. In 2006, Kuijpers D et al. compared the effects of ALA and MAL in the study of photodynamic therapy for nodular basal cell carcinoma. Clinical trials found that there was no statistical significance between the two in terms of short-term efficacy and adverse reactions after treatment. Compared with ALA, MAL is more easily accepted by patients because of its less pain during treatment. In some related PDT studies, it was found that after the photosensitizer (ALA) entered the lesion, the enrichment of ALA in the target cells was different at different times. Fluorescence images were collected after different treatment times, and it was found that the fluorescence intensity reached a peak at 3~10h. However, in facial rejuvenation treatment, is the effect more obvious the longer the photosensitizer is applied? Some scholars used MAL as a photosensitizer and compared half of the face. One side was treated with red light after applying MAL for 1h, and the other side was treated with MAL for 3h and then irradiated with red light. After 3 treatments, the skin firmness and refinement of the side applied for 3h were more obvious, but the skin texture of the side applied for 1h was also significantly improved. However, the side applied for 3h had more obvious side effects (such as erythema, edema, etc.). Reducing the contact time between the photosensitizer and the skin can achieve the treatment purpose and reduce the occurrence of side effects. Clinically, the time for applying photosensitizer is shortened to 0.5~1h.
After PDT treatment, patients should avoid direct sunlight for at least 24 hours and pay attention to sun protection. The treated area may experience erythema, edema, and crusting, and the skin may be dry and tight, but skin care products should not be used immediately to avoid allergic or irritant dermatitis. The most common complication of PDT skin rejuvenation treatment is excessive sunburn. Patients need to be repeatedly told to avoid direct sunlight and apply sunscreen. If this complication occurs, ice should be applied to the treated area, and the treated area should be raised to reduce edema. Bacterial and viral infections are rarely seen with this treatment.
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