Asclepion MeDioStar, User Manual, Page: 55 / 94

Application
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6.2.1 Interaction of laser beam and tissue
The goal especially for dermatological and aesthetic treatments is to remove the lesions to be treated
or the unwanted lesions without any side effects. The selective phototermolysis method introduced
by Anderson as a treatment concept in 1983 ensures an effective damage of the target and the
simultaneous protection of the skin surrounding it.
Therefore, the following aspects are to be observed for a successful treatment:
Absorption of the laser beam wave length
The absorption of the laser beam must be higher in the target (e.g. the melanin in the hair or the
blood in the vessel) than the one in the surrounding skin mainly consisting of water. The higher the
absorption in the target the greater the heat generated; the lower the absorption in the surrounding
skin area, the lower the unwanted heating of the skin.
The wave length range of the MeDioStar device in the near infrared (IR) between 800nm and
950nm has a relatively high melanin and blood absorption. The wavelengths of the different
handpieces are optimal adjusted within this range to the individually planned indication.
However, you have also to consider the absorption of melanin in the epidermis of dark skin that is
generally not desired (apart from the treatment of benign pigmented lesions) and can produce side
effects like stronger bad sensation, hyper- or hypo-pigmentation. Therefore, the Rubin and the
Alexandrit lasers having wave lengths of 694nm and 755nm, respectively, are less suited for treating
dark skin types due to their relatively high melanin absorption. The wave length range of the
MeDioStar is considerably better suited.
Figure 37: Absorption coefficients depending on the wavelength of the laser beam
Spot size
The spot size must be so large that the target located some millimeters beneath the surface of the
skin (e.g. a hair root or vessel) is reached with a sufficiently high energy density (FLUENCE). This
requirement is met by the MeDioStar laser device.
It must be principally ensured that a larger spot heats a larger volume in the skin. Therefore, the
required fluence is lower for larger spots.