■ Laser Removal of Tattoos
For Q-Switched laser tattoo treatment to be effective, the absorption peak of the pigment must match the wavelength of the laser energy. Similar colors may contain different pigments, with different responses to a given laser wavelength, and not all pigments absorb the wavelengths of currently available medical lasers.
Tattoos absorb maximally in the following ranges: red tattoos, from 505 to 560 nm (green spectrum); green tattoos, from 630 to 730 nm (red spectrum); and a blue-green tattoo, in two ranges from 400 to 450 nm and from 505 to 560 nm (blue-purple and green spectrums, respectively). Yellow tattoos absorbed maximally from 450 to 510 nm (blue-green spectrum), purple tattoos-absorbed maximally from 550 to 640 nm (green-yellow-orange-red spectrum), blue tattoos absorbed maximally from 620 to 730 nm (red spectrum), and orange tattoos absorbed maximally from 500 to 525 nm (green spectrum). Black and gray absorbed broadly in the visible spectrum, but these colors most effectively absorb 600- to 800-nm laser irradiation.
Three types of lasers are currently used for tattoo removal: Q-switched ruby laser (694 nm), Q-switched Nd:YAG laser (532 nm, 1064 nm), and Q-switched alexandrite (755 nm) laser (Adrian 2000). The Q-switched ruby and alexandrite lasers are useful for removing black, blue, and green pigment (Alster 1995). The Q-switched 532-nm Nd:YAG laser can be used to remove red pigments, and the 1064-nm Nd:YAG laser is used for removal of black and blue pigments (Kilmer et al. 1993). Since many wavelengths are needed to treat multicolored tattoos, not one laser system can be used alone to remove all the available inks (Kilmer 1993; Levine 1995).
There is still much to be learned about removing tattoo pigment. Once ink is implanted into the dermis, the particles are found predominantly within fibroblasts, macrophages, and occasionally as membrane-bound pigment granules.
Exposure to Q-switched lasers produces selective fragmentation of these pigment-containing cells. The pigment particles are reduced in size and found extracellularly. A brisk inflam matory response occurs within 24 h. Two weeks later, the laser-altered tattoo ink particles are found repackaged in the same type of dermal cells.
It is not yet clear how the liberated ink particles are cleared from the skin after laser treatment. Possible mechanisms for tattoo lightening include: (1) systemic elimination by phagocytosis and transport of ink particles by inflammatory cells, (2) external elimination via a scale-crust that is shed, or (3) alteration of the optical properties of the tattoo to make it less apparent. The first of these appears clinically and histologically to be the dominant mechanism.
There are five types of tattoos: professional, amateur, traumatic, cosmetic, and medicinal. In general, amateur tattoos require fewer treatment sessions than professional multicolored tattoos. Densely pigmented or decorative professional tattoos are composed of a variety of colored pigments and may be particularly difficult to remove, requiring 10 or more treatment sessions in some cases (Fig. 3.5). A 100% clearing rate is not always obtained and, in some instances, tattoos can be resistant to further treatment. Amateur tattoos are typically less dense, and are often made up of carbon-based ink that responds more readily to Q-switched laser treatment (Fig. 3.6). Traumatic tattoos usually have minimal pigment deposited superficially and often clear with a few treatments (Ashinoff 1993) (Fig. 3.7). Caution should be used when treating gunpowder or firework tattoos, because the implanted material has the potential to ignite and cause pox-like scars.
After obtaining informed consent (Fig. 3.8), the following options are considered.
The approach to treatment will vary with the chosen laser and whether the pigmented lesion to be treated is epidermal, dermal, or mixed. Tattoos may show a different response (Tables 3.4-3.6).
Fig. 3.5. Professional tattoo. Partial clearing after four treatments
Fig. 3.6. Amateur tattoo. Complete clearing after two treatments
Fig. 3.6. Amateur tattoo. Complete clearing after two treatments
Q-Switched Ruby Laser (694 nm)
The first Q-switched laser developed was a ruby laser. Current models employ a mirrored articulated arm with a variable spot size of 5 or 6.5 mm, a pulse width of 28-40 ns and a maximum fluence of up to 10 J/cm2. The 694-nm wavelength is most well absorbed by melanin.
Because hemoglobin absorbs 694-nm light poorly, the ruby laser treats pigmented lesions very efficiently.
Most lentigines and ephelides clear after one to three treatments with the Q-switched ruby laser (QSRL). Cafe-au-lait macules, nevus spilus, and Becker's nevus respond moderately well. Recurrences are frequent with these
lesions, especially when incomplete clearing is obtained. The QSRL has become the treatment of choice for dermal pigmented lesions like nevus of Ota or Ito. The long wavelength, the big spot size and the high delivered energy per pulse generates a high fluence deep in the tissue. This all leads to efficient targeting of deep melanocytes. As effective as other Q-switched lasers are for removing black tattoo ink, the QSRL is one of the better lasers for removing dark blue or green ink. Removal of red tattoo ink is problematic given that the QSRL is a red light source and is not well absorbed by the red ink particles. Yellow ink does not respond to QSRL treatment because the absorption of yellow inks is very low in this laser's red to near-infrared spectrum of delivered light.
When selecting the energy level for treatment with the QSRL, immediate tissue whitening with no or minimal tissue bleeding should be observed. The required energy level is determined by the degree of pigmentation or the amount and color of the tattoo ink. The 6.5-mm spot is recommended for most lesions, with an initial fluence of 3-5 J/cm2. The excellent QSRL melanin absorption frequently leads to transient hypopigmentation, which may take months to resolve. Rarely (in i%-5% of cases), one sees permanent depigmentation.
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