755nm Alexandrite laser Yag laser hair removal technology introduction

Background: Although laser hair removal has been performed in recent years to remove or reduce unwanted dark hair, the technology, including appropriate methods for different skin types and body areas, has not been optimized.

Objective: We review the principles of laser hair removal and report a retrospective study of 322 patients who underwent 3 or more long-pulsed alexandrite laser hair removal between January 2000 and December 2002. retrospective study.

Methods: Before treatment, patients were evaluated by a doctor and informed of the mechanism, efficacy and possible side effects of the treatment. According to the Fitzpatrick classification, patients are classified by skin type. Those with systemic disease, a history of sun sensitivity, or the use of drugs known to cause photosensitivity were excluded from laser treatment. All treatments were performed using a long-pulse alexandrite laser with constant spot size (18 mm) and 3 ms pulse width, which applied 755 nanometers of energy. The treatment is repeated at different intervals depending on the body part to be treated.

RESULTS: The total hair loss rate was estimated to be 80.8% in all patients regardless of skin type. After treatment, there were 2 cases of hypopigmentation and 8 cases of hyperpigmentation. No other complications were reported. CONCLUSIONS: Long-pulse alexandrite laser treatment can meet the expectations of patients who wish to have permanent hair removal. Careful patient examination and thorough patient education prior to treatment are critical to patient compliance and the success of this technique.
Currently, lasers of various wavelengths are used for hair removal, from the 695 nm ruby laser at the short end to the 1064 nm Nd:YAG laser at the long end. 10 Although shorter wavelengths do not achieve desired long-term hair removal, longer wavelengths are too close to the light absorption rates of oxygenated hemoglobin and melanin to be fully effective. The alexandrite laser, located almost in the middle of the spectrum, is an ideal choice with a wavelength of 755 nm.

The energy of a laser is defined by the number of photons delivered to the target, in joules (J). The power of a laser device is defined by the amount of energy delivered over time, in watts. Flux is the amount of energy (J/cm 2) applied per unit area. Spot size is defined by the diameter of the laser beam; The larger size allows for more efficient transfer of energy through the dermis.

For laser treatment to be safe, the energy of the laser must destroy the hair follicle while preserving the surrounding tissue. This is achieved by applying the principle of thermal relaxation time (TRT). The term refers to the cooling duration of the target; Selective thermal damage is accomplished when the energy delivered is longer than the TRT of the adjacent structure but shorter than the TRT of the hair follicle, thus not allowing the target to cool and thus damaging the hair follicle. 11, 12 Although the TRT of the epidermis is measured at 3 ms, it takes nearly 40 to 100 ms for the hair follicle to cool. In addition to this principle, you can also use a cooling device on the skin. The device both protects the skin from possible thermal damage and reduces pain for the patient, allowing the operator to safely deliver more energy.

Post time: Aug-12-2022