Medical beauty techniques play a crucial role in the pursuit of perfect skin. Today, we focus on a highly acclaimed non-invasive skin treatment technique - intense pulsed light (IPL). This article will delve into the working principle and clinical mechanism of IPL.
1、Composition of Strong Pulse Light Therapy Device
The intense pulse light therapy device usually consists of a main unit and a handheld device. The main unit is equipped with a power supply, control system, and circulating water cooling system.
2、The working principle of the intense pulse light therapy device
The light source of the intense pulse light therapy device is a xenon lamp located inside the hand tool. Its working principle is that the control circuit inside the host outputs control signals to charge the energy storage capacitor and discharge it in a very short time, causing avalanche ionization of xenon gas in the xenon lamp inside the hand tool. Xenon gas converts and releases the charged energy in the form of high-intensity light radiation, and this discharge process is a light pulse. The energy, number of sub pulses, pulse width and other parameters of the light pulse are also controlled by the control circuit inside the host according to the parameters set by the user.
The wavelength range of the pulsed light output mentioned above is usually between 400-1200nm, which is incoherent and non parallel multi-color broadband light. For different indications and skin types of patients, different wavelengths of light need to be used. To achieve this goal, the pulse light emitted by the xenon lamp needs to be filtered. There are usually two ways of filtering. One is to install a removable filter on the hand, and the surface coating layers of different filters are different, which can filter light of different wavelengths. During treatment, only the filter needs to be replaced to switch the desired wavelength, making it more convenient to use; Another method is to use a fixed wavelength handheld device, which needs to be replaced with different devices to emit pulsed light of different wavelengths during use.
3、Scope of application of intense pulsed light therapy device
The intense pulsed light therapy device is used to treat vascular skin diseases and superficial pigmentary skin diseases, reduce hair, and treat mild to moderate inflammatory acne (acne vulgaris).
4、The mechanism of action of the intense pulsed light therapy device
1.Pigmentary skin disease
Melanin in the skin, as a target tissue, absorbs the entire visible light spectrum, and the absorption rate gradually decreases with the increase of light wavelength. Generally speaking, below 800nm, melanin has strong absorption in the spectrum, while the absorption of melanin in the near-infrared spectral range gradually decreases. The characteristics of tissue effects will vary depending on the pulse width of the absorbed light energy. Ordinary pigment particles usually have a thermal relaxation time of tens to hundreds of nanoseconds, and the pulse width of strong pulsed light is significantly longer than the thermal relaxation time of pigment particles. When treating pigmentary lesions, melanin can selectively absorb the IPL spectrum, producing selective light absorption. However, due to the wide pulse width, non selective thermal coagulation is often produced based on the size of pigment particles and the relationship between pulse width and particle thermal relaxation time, and the coagulated tissue is eliminated by phagocytic cells.
2.Vascular skin diseases
The main structure of the vascular wall is epithelium and proteins, which are white in color and have less absorption of light. But the blood flowing inside, namely hemoglobin, has color. According to the theory of selective photothermal action and its extended theory, hemoglobin has a maximum absorption peak at 418nm, two secondary peaks at 542nm and 577nm, and a lower absorption peak near 940nm. Specific wavelengths of IPL can be strongly absorbed by hemoglobin. When the pulse width of the light wave is adapted to the thermal relaxation time of the treated blood vessel, it will generate temperature rise through energy conversion and aggregation, and mainly concentrate thermal energy in the blood vessel and its adjacent tissues. When the temperature rises to a certain extent, it can cause the contraction, denaturation, coagulation, and even necrosis of the endothelial and wall proteins of capillaries, resulting in capillary lumen occlusion and gradual replacement by fibrous tissue, ultimately achieving the goal of treating diseased blood vessels
3.Reduce hair
Hair has a growth cycle, which can be roughly divided into latent period, growth period, and decline period. During the growth period, hair has complete structures such as hair follicles and hair shafts. Yellow people's hair follicles contain pigments, which are mostly black in color. However, during the latent and declining periods, there is a lack of follicle structure in the hair. Removing excess hair is achieved by utilizing the anatomical structure of hair, using strong pulsed light with a certain penetration depth and wavelengths that can absorb melanin well. This allows hair follicles and hair shafts that have been irradiated with light to absorb a large amount of light energy, which is then converted into heat and transmitted to the ends of the hair follicles through the proteins inside the hair. The entire hair is heated, and the heat is transmitted to the hair follicles, causing coagulation necrosis between the proteins and cells. Ultimately, due to the necrosis of growing cells, the entire hair is shed.
4.Acne
The mechanism of treating acne vulgaris mainly involves stimulating the generation of singlet oxygen, which is a cytotoxic substance that can destroy Propionibacterium acnes in sebaceous glands, thereby inhibiting the formation of acne. The porphyrin absorption peaks produced by Propionibacterium acnes in sebaceous glands are 415, 504, 576, 538, and 630 nm, with the highest absorption wavelength being 415 nm. These wavelengths can cause photodynamic reactions after exposure to light, stimulating the conversion of porphyrins produced by Propionibacterium acnes into singlet oxygen, reducing the formation of inflammatory acne. The strong pulsed light dual band filter mainly produces wavelengths in the 400-600nm and 800-1200nm bands, filtering out the middle 600-800nm band. Unlike single band filters, the 400-600nm band covers the maximum absorption peak of porphyrin, while the 800-1200nm band reaches the sebaceous gland at a depth of 800-1200nm, causing it to contract and reducing the anaerobic environment required for bacterial growth. This avoids energy being competitively absorbed by melanin targets in the 600-800nm band, thereby affecting the absorption of Propionibacterium acnes.
5、Summary
The intense pulsed light therapy device emits a wide spectrum of light ranging from 400 to 1200 nm. After filtering out unwanted emitted spectra, specific wavelength bands of pulsed light are formed and applied to the skin at the treatment site. After selective absorption by different target color groups, photothermal effects are generated to promote the decomposition, degeneration, or necrosis of target tissues, thereby achieving the effects of treating vascular skin diseases, superficial pigmentary skin diseases, reducing hair, and treating acne vulgaris.
