Laser hair removal
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Fig. 1. Exposure of the hair to the laser emission.
| The new method of hair removal (QOOL-epilation) is highly selective, it destroys the shaft of the hair and does not influence the surrounding tissues.
The patient can feel only a light pricking at the moment of hair getting to the beam aperture. At the second exposure of the same area the patient does not feel anything, neither at exposure of the area where the hair does not grow, for instance, palm or back of the hand.
Almost a complete absence of painful sensations allows to treat with success such areas as face, underarm, bikini. There is no need in anaesthesia or cooling of the skin.
For the new method of hair removal the patient’s degree of skin pigmentation does not matter. The emission parametres are set up so that destroying effect should be produced only on melanin of the hair and should not affect melanin of the skin. Owing to this fact the patient can take sunbaths or visit | 
Fig. 2. Coagulation and fragmentation of the hair.
| solarium both before and after the epilation. Therefore, the new method allows to remove hair safely, without any risk to the patient. How can it be achieved?
The mode of QOOL-epilation is based on the application of a particular kind of laser emission – millisecond train of nanosecond pulses.At the exposure of melanin (pigment) of hair to a nanosecond high-powered pulse the coefficient of emission absorption by melanin increases drastically (effect of non linear absorption) in comparison with common absorption coefficient.
Using a train of nanosecond pulses with total duration not exceeding the PTR of the hair (PTR — period of thermal relaxation — a period, during which the heated object has time to pass the excess of heat to surrounding tissues) and intervals between pulses comparable to the PTR of the skin allows to heat hair selectively without overheating the skin. The hair accumulates the heat from pulse to pulse and the skin has time to cool during the intervals between pulses. This mechanism is applicable only while using Q-switched pulses of a certain energy density.
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Fig. 3. Destruction of the hair at all its length.
| Except heating the hair undergoes also a mechanical influence resulting from the fact that a part of the energy of nanosecond pulse is spent to create an acoustic wave, that spreading from melanin particle destroys mechanically the structure of the hair.
The energy parametres of pulse trains are selected in order that the power of each pulse should be sufficient to increase the absorption coefficient of melanin and to fragmentize a small volume of hair. Owing to that the pulse energy is spent more efficiently and surrounding tissues are not damaged. Each pulse destroying a part of the hair makes way for next one, that ensures a layer-by-layer fragmentation of the whole hair.
The wavelength used for epilation (1079 nm) penetrates deep into the skin that ensures the epilation of all hair. The parametres of pulse train (duration, intervals between pulses, energy of pulses) are different for removal of different hair. To facilitate the device handling all the necessary parametres are poked in the memory of the built-in computer and set up automatically according to the hair and skin characteristics of the patient chosen by the operator.
Therefore the "LINLINE" method combines advantages of traditional methods of epilation: those of long pulse one used in alexandrite, ruby, diode, neodymium epilators and those of short pulse method, based on fragmentation of hair by single nanosecond pulses, but it does not have their disadvantages.
The short pulse method is characterized by penetration depth insufficient to remove hair completely (See Fig.).
At the long pulse method the time of exposure to a laser pulse exceeds greatly the PTR of the hair (2-5 milliseconds) and a big quantity of heat has time to flow into the skin. Melanin of the skin also absorbs the emission energy, and as the pulse influences it for a much longer period, than the PTR of the skin, the skin has no time to cool. It results in overheating of the skin and its coagulation. The using of cooling systems reduces the pain threshold, but does not affect the overheating of deep layers of the skin and does not reduce the risk of scarring.
Application: hair removal on all phototypes of skin.
Complete treatment: one session of procedures for hair in the active phase of growth (anogene).
Laser type: Nd:YAP/Q-switched (dark hair), RUBY/Q-switched (fair hair).
The method is patented and can be applied only by LINLINE GmbH.
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