Non-ablative laser and phototherapy skin rejuvenation principles and common technology equipment comparison

Summary and key points

1. Non-ablative skin resurfacing is a safe and effective method to improve skin photoaging and other problems.

2. Non-ablative skin resurfacing provides the minimum time between treatments while achieving appropriate results.

3. Non-ablative skin resurfacing refers to the change of cellular and non-cellular components of the skin without the creation of open wounds.

4. Medical factors and patient expectations should be carefully considered when selecting patients

5. Non-ablative means rarely require anesthesia other than local anesthesia.

6. Complications are rare when the treatment is performed with adequate preparation.

7. Photodynamic therapy maximizes laser-tissue interaction and subsequently improves photoaging.

8. Laser parameters need to be adjusted to minimize pigmentation in skin types IV-V.

9. Patients can resume normal activities 1-2 days after non-ablative treatment.

10. For patients with limited downtime, multiple treatments spaced 2-3 months apart can achieve better results.

Introduction

Skin rejuvenation seeks to optimize efficacy with minimal downtime by leveraging the strengths of both laser and non-laser treatments. Ablative lasers are the gold standard for facial rejuvenation, at least for the treatment of fine wrinkles. Although ablative treatments can achieve predictable aesthetic results, the risks of scar infection, depigmentation, and prolonged downtime reduce their appeal. Patients are increasingly trying to balance the efficacy of skin rejuvenation with downtime. Non-ablative skin rejuvenation treatments generally do not require advanced anesthesia and usually require only topical anesthesia. As a result, non-ablative treatments have an important place in skin rejuvenation treatments.

Because the term "non-ablative skin rejuvenation" is sometimes used casually, it is important to clearly define it. In its purest form, non-ablative skin rejuvenation involves enhancing the texture of the skin without physically exfoliating or vaporizing the skin. Ablative treatments involve the removal of part or all of the epidermis and sometimes also part of the dermis by vaporization. This chapter focuses on non-fractional non-ablative skin rejuvenation. There are two ways to selectively damage the dermis (and/or deep epidermis):

1. Targeting the dispersed chromophores in the dermis and/or the dermal-epidermal junction.

2. Using mid-infrared lasers with a wavelength of 13-155 μm, so that water absorption of the laser is low enough to achieve a relatively deep laser penetration depth (only 50% laser attenuation at a depth of 300-1500 mm).

Photodamage treatment can be divided into many types, and the appropriate treatment plan is generally selected based on the laser-tissue interaction described above. The treatment goal is to maximize skin resurfacing by reducing telangiectasia and lentigo and increasing dermal remodeling.

Laser and non-laser systems used for non-ablative skin resurfacing include visible light (400-760 nm), near infrared (760-1400 nm), mid-infrared (1.4-3 μm), radio frequency (RF) intense pulsed light (IPL) and light-emitting diodes (LED) that emit different light sources.

Each treatment can act on different target tissue components and cause dermal remodeling without epidermal exfoliation. Most researchers believe that photothermal heating of the dermis can:

(1) increase collagen synthesis by fibroblasts

(2) induce dermal matrix remodeling by altering mucopolysaccharides and other components of the dermis.

Others believe that the interaction between laser/light and intracellular molecular components changes the structural components of cells and the function of enzymes. Changes in different components of cells, from enzymes, cell wall composition to nucleic acids, may change the cell's environment and metabolic efficiency.

Equipment used for non-ablative skin reconstruction

Visible light/vascular laser

-532nm potassium titanyl phosphate (KTP)

-585nm/595nm pulse dye

Near infrared laser

-1064nm Qs neodymium:yttrium aluminum garnet (Nd YAG)

-1064nm long pulse neodymium:yttrium aluminum garnet (Nd:YAG)

-1320nm neodymium:yttrium aluminum garnet (Nd:YAG)

Mid-infrared laser

-1450nm semiconductor

-1540nm Erbium: Glass

Intense Pulsed Light (IPL) (500-1200nm)

Radio Frequency (RF) System

Light Emitting Diode (LED

Studies have shown that photodynamic therapy (PDT) with aminolevulinic acid (ALA) can enhance the effect of laser or other light sources. A variety of lasers and light sources have been used for photoactivation of the protoporphyrin zone to improve skin rejuvenation 

Non-ablative skin rejuvenation techniques are usually used to reverse dermal photoaging. This damage is directly related to the patient's age and the degree of exposure to ultraviolet light. Ultraviolet B (UVB) can cause changes in nucleic acids because it can interact with epidermal keratinocytes and induce cellular atypia. Prolonged exposure to long-wave ultraviolet A (UVA) promotes the formation of oxygen free radicals, induces changes in the normal homeostasis of angiogenesis, apoptosis, pigment production in melanocytes, immune cell dysregulation, cytokine dysregulation, changes in dermal matrix composition, and blocked transcription, translation, and replication of the genetic code. Clinical manifestations of photoaging appear together The histological changes include epidermal atrophy, disappearance of the reticular structure, accumulation of elastic fibers in the papillary dermis, disordered and reduced collagen production, and increased blood vessels. These changes caused by ultraviolet light are related to the clinical manifestations of photoaged skin, including skin relaxation, atrophy and brittleness, increased wrinkles, capillary dilation, and changes in the overall color, texture and uniformity of the skin. Therefore, the goal of skin rejuvenation is to replace the damaged epidermal or dermal components with stronger new skin. Doctors should try their best to change the quality of keratinocytes and the pigment production in melanocytes, which are two key factors in epidermal photodamage. Epidermal photodamage rejuvenation usually focuses on how to improve the quality of fibroblasts and inhibit their degeneration. Studies have shown that the antioxidant capacity and collagen synthesis capacity of fibroblast cultures increased after irradiation with 532nm and 1064nm lasers for milliseconds and nanoseconds.

Mid-infrared laser

There is clinical and histological evidence that non-ablative skin rejuvenation can be achieved using mid-infrared lasers. 1320nm The Nd:YAG laser (Ciellulu K6 https://www.ciellululaser.com/product/ciellulu-q-switched-nd-yag-laser-liffan-k6.html ) is a non-ablative mid-infrared laser commonly used for skin rejuvenation. In combination with surface cooling, this laser can achieve collagen remodeling without damaging the epidermis. Nonspecific thermal damage to the dermis, targeting water, causes edema, vascular changes, and rearrangement of fibroblasts in the dermal matrix. The healing process can produce mild wrinkle reduction. 1450nm semiconductor lasers are also used for non-ablative skin rejuvenation in the same manner as 1320nm

Nd:YAG.

Similarly, 1540nm Er:Glass lasers can also induce water heating, thermal damage, and new collagen formation in tissues. The penetration depth of the laser in this wavelength range is between the penetration depths of 1320nm (deepest) and 1450nm (shallowest) lasers. When developing a treatment strategy for mid-IR wavelength lasers, the laser penetration depth should be equal to the depth of solar elastosis.

Each non-fractional mid-IR laser uses a cooling system to minimize epidermal damage and pigmentary changes. The 1320nm Nd:YAG uses a pre- or post-laser spray, while the 1450nm diode laser uses a cryogen before, during, and after the laser pulse. The combination of long wavelength lasers and surface cooling systems makes these lasers suitable for W, V, and V types of the Fitzpatrick skin classification. However, there is a risk of cryoinjury, especially for the 1450nm system, which has a long total spray time (up to 220ms). The addition of a 1320nm laser with a shorter spray time and a 5°C sapphire lens to the 1540nm Er:Glass laser system does not cause cryoinjury. The side effect profile of each laser is directly related to the energy level used to treat wrinkles or acne scars. Although studies have shown that these lasers are adequate for most cases, operators must be careful to avoid pigment changes and rare scarring events, which are often caused when too high energy density is used.

Ciellulu's latest Diode Laser (https://www.ciellululaser.com/diode-laser) devices include the S500 (https://www.ciellululaser.com/product/ciellulu-s500-1500w-diode-laser-haire-removal-skin-rejuvenation-machine.html) and K3 (https://www.ciellululaser.com/product/ciellulu-k3-diode-laser-4-wavelength-808-755-940-1064nm-hair-removal-machine.html), which can output laser pulses of four different wavelengths: 755nm, 808nn, 904nm, and 1064nm.

TIPS

Caution should be exercised when using high energy densities in small areas (i.e., upper lip) as high energy densities may cause overall heating and increase the risk of hyperpigmentation or scarring.

Intense Pulsed Light

IPL emits a wide range of laser wavelengths, from 400 to 1200 nm, which can target a variety of structures. Although these devices do not emit monochromatic, collimated, or coherent light, they still utilize selective photothermolysis. IPL can be used to target specific chromophores, selecting specific wavelengths in the range of 400 to 1200 nm to target specific chromophores and using corresponding filters to avoid other chromophores. Short wavelengths can be used to treat patients with lighter skin, or the spectrum can be "red-shifted" with the help of filters or electronic modulation to minimize melanin absorption in patients with darker skin. IPL can selectively use the hemoglobin absorption peak to target vascular structures. Finally, for non-ablative skin rejuvenation, water in the dermis can be targeted to allow photothermal effects to induce neocollagen formation.

The uses and potential risks of IPL are related to its diversity. The appropriate IPL wavelength can be selected to target different chromophores (water, melanin, and hemoglobin) to treat a variety of skin conditions. There are a variety of IPL devices on the market with a variety of designs and treatment parameters. For example, Ciellulu's MULA K2, https://www.ciellululaser.com/product/ciellulu-mula-k2-bbl-dpl-beauty-machine-for-skin-care-and-hair-removal.html , has 11 different wavelength wave plates and 4 precision treatment heads to treat a variety of different skin problems. Although newer systems have improved user presets, it is important to be familiar with one or two IPL systems, as each system has a different interface, wavelength range, filter, power output, pulse profile, cooling system, and spot size. Some of these different parameter combinations make it difficult to compare different IPL systems. For example, some IPL devices calculate their energy levels based in part on theoretical modeling and photon recycling, while others simply determine their energy levels based on the actual output energy at the sapphire or quartz window at the top of the handle. Therefore, even if the settings on the display panel of two IPL devices are the same, it does not mean that they can produce the same treatment effect. For example, one IPL is equipped with a spectrophotometer (color temperature meter). Through Bluetooth technology, the photometer transmits the patient's pigment level directly to the IPL. Then, the recommended test reference value for a specific skin area is given through the user interface graphic.

TIPS

Ensure good contact between the handle and the skin while the skin is taut. This can achieve the maximum laser penetration depth, and the spot can be treated evenly on the skin, which helps to reduce the risk of post-symptomatic pigmentation. When using IPL devices to treat facial skin, especially for dark pigmented skin, it is worth noting that the human face has certain wheels and is very uneven, and most IPL devices use right-angle handles, which makes it difficult to achieve good contact around the nose and eyes.

Finally, although IPL devices can be used to treat a variety of different diseases, people still use radiofrequency technology to supplement and improve the effects of IPL devices (Elos, Syneron). Bipolar radiofrequency has a preference for warmed tissue. Given the nature of this technology, an IPL system is first used to heat the target chromophore, and then RF technology is used to target the currently "hot" tissue target. The contact cooling mechanism helps prevent epidermal damage and keeps tissue heat contained to the dermis. Studies have shown that this synergistic technology can effectively treat photoaging and reduce wrinkles, sun spots, and telangiectasia.

Light Emitting Diodes

LEDS used for photoaging treatments consist of a large group of small bulbs that emit low-intensity light. Some companies have miniaturized these devices into handheld products that can be used at home, while most professionals use devices that treat the entire face at once. One of the advantages of LED devices is that they are well tolerated by patients. Patients do not feel pain, so large areas of skin can be treated at the same time.

Typically, LED devices can emit light in a range of wavelengths. These devices can emit a variety of wavelengths, from blue light to infrared light. Depending on the wavelength and treatment parameters, LEDS can emit light in milliwatts within a small range of certain peak values. For example, if the dominant wavelength of the LED we choose is 500nm, the device can emit light in the range of 480~520nm.

The interaction between the TED device and the skin is not yet clear, although most researchers believe that light regulation of cell receptors, organelles, or existing protein products is involved to some extent. Unlike most of the devices discussed above, the low-temperature interaction between the device and the extracellular matrix and fibroblasts can reshape existing collagen, increase collagen production by fibroblasts, and inhibit collagen activity, thereby achieving the effect of reducing wrinkles.

One example of an LED system is the Gentle Waves device, which can generate 588nm yellow light pulses with a pulse duration of 250ms and a pulse interval of 10ms, a total of 100 pulses, and a total light dose of 0.1J/cm.

Photodynamic therapy

Over the past 20 years, photosensitizing drugs have played an increasingly important role in medical and cosmetic dermatology. 25% 5-aminovaleric acid (5-ALA, a "prodrug") can be absorbed by rapidly proliferating epidermal and dermal cells and converted into photoreactive products in the hemoglobin pathway, mainly protoporphyrin IX. Subsequently, protoporphyrin IX is activated by specific waves. Long light activation, as shown by the absorption peak in Figure 51, produces singlet oxygen and destroys cells.

Many light sources have been used for PDT (Box 53). This variation may be due to the fact that the protoporphyrin region has multiple absorption peaks. The maximum absorption peaks are at 417nm, 540nm, 570nm and 630nm. Both PDl IPL and LED devices have been used to activate protoporphyrin IX. There are many variables that affect the immediate PDT response, including ALA incubation time, skin preparation before ALA application, degree of skin photodamage, anatomical location, light dose, wavelength range and power density. In general, low power density (i.e., continuous wave light sources) generate more singlet oxygen than pulsed light. In addition, we have found that applying an anesthetic cream at the same time as the ALA solution can accelerate the absorption of ALA, thereby accelerating the formation of protoporphyrin, resulting in a stronger response.

Pay attention to protection during laser treatment

The doctor should take photos to record the patient's condition before treatment. The position of the patient and the position of the curtain should ensure that the doctor can access the entire treatment area. Generally, when treating photodamaged areas such as the face, neck, chest and forearms, let the patient lie on his back. Then wear goggles or eye shields (internal or external depending on the treatment area) to provide appropriate eye protection. For patients who have taken appropriate eye protection measures, they should be informed that they may see flashes during treatment. Even if they have put on goggles or eye shields, many patients still worry that the laser will cause danger when they see flashes. Patients should be informed that they have taken adequate protection measures for them, so that they can receive treatment with more peace of mind even if they see flashes near the eye shields.