Intense pulsed light (I PL) systems are high intensity pulsed light sources which emit polychromatic light in a broad wavelength spectrum of 515-1200 nm. The emitted wavelengths determine not only the absorption pattern of the emitted light but also the penetration depth of the light. With the aid of different cut-off filters (515-755 nm), which only allow a defined wavelength emission spectrum, the optimal wavelength spectrum can be filtered to correspond to the depth of the target structure (i. e., hair follicles). Similarly, the emitted wavelengths can be adopted to the patient's individual skin type. Higher cutoff filters reduce the emission of melanin-absorbing wavelengths; thus being safer for darker skin types.
The pulse duration of IPL systems can be set to a wide range of parameters. The use of single pulses is possible. In the alternative, high flu-ences can be divided into multiple pulses. The intervals between individual pulses can be set at values between 1 and 300 ms. This delay, in theory, allows the epidermis and smaller vessels to cool down between pulses while the heat is retained in the larger target (hair follicles). This results in selective thermal damage. The extent of maximum delivered fluences and the spot size vary, depending on utilized IPL.
When an IPL is used, a transparent refrigerated gel is placed on the skin to cool the epidermis and to improve light delivery to the skin during treatment. The large rectangular spot sizes associated with most IPL hand pieces allows a large number of hairs to be treated simultaneously.
The IPL delivery of a broad range of wavelengths has some advantages. The presence of longer wavelengths provides better penetration depth into the dermis, while shorter wavelengths can be filtered out to protect the epidermis in darker-skinned individuals. Shorter emitted wavelengths may also be useful to treat red-brown hair (Ross et al. 1999).
One of the greatest technical advantages of IPL systems is the large exposure area that is used. This improves the resultant damage of deep follicles. A disadvantage is that the rectangular spot size prevents treatment of hair-bearing areas on marked convexities or concavities (Ross et al. 1999).
Several studies have demonstrated the long-term efficacy of IPL hair removal devices (Gold et al. 1997; Weiss et al. 1999). In one study of 67 subjects of Fitzpatrick skin phototypes I-IV, mean hair loss was 48% at 6 months or more after a single treatment. In another study, after a single treatment, hair reduction ranging from 33% to 60% was observed at 6 months after treatment. Further studies of 14 subjects treated with this technology and followed for > 12 months after their last treatment showed a mean of 83% hair reduction was obtained after two to six treatments. As would be expected, repeated treatments appear to improve outcome. Despite this, some have suggested that more than three IPL treatments do not appear to increase the success rate. Not all would agree with this. Finally, treatment with IPL, with and without bipolar radiofrequency, has been said to be useful for the treatment of light-colored hair. Generally, more treatments are required and the results are not expected to be as good as those seen when treating darker-colored hairs.
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