Clinical Review

Tattoo Removal by Q-Switched Laser

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Before initiating laser therapy (or referring the patient for it), the primary care clinician should collect a history regarding the tattoo’s age and etiology, as well as the patient’s tanning habits, in order to recommend the best treatment. As stated earlier, professional tattoos generally require more treatments than amateur tattoos. Distally located tattoos are the most difficult to remove.1,13

Q-Switched Laser Types
The most common Q-switched lasers are:

• Q-switched ruby laser

• Q-switched Nd:YAG (neo­dymium:yttrium aluminum garnet) laser

• Q-switched alexandrite laser (see table1,4,6,14).

The choice of laser type is based on several factors, including the presumed absorption spectrum of the target, the desired depth of penetration, the size of the target particle, and the laser’s wavelength and pulse duration.11

Black and India inks absorb broadly across the spectrum. In the case of blue, yellow, or orange pigment, the optimal wavelength for pigment absorption is in an adjacent color. Green pigment absorption spectra vary due to the pigment’s multiple components. The spectra of white, yellow, and “flesh-colored” pigments do not have absorption peaks at the wavelengths of currently used Q-switched lasers; this explains their resistance to removal.11

Use of the Q-switched ruby laser (QSR) is indicated for the removal of black, blue-black, and dark blue pigments. Mixed results have been reported for removal of green and medium blue pigments, and poor results for red, orange, and pale blue. Six treatments at three-week intervals have been reported to yield clearance of 75% or greater in only about 25% of professional, dark-colored tattoos.1,15

Since this laser’s wavelength (694 nm) is absorbed by melanin, its use may result in transient hypopigmentation, depigmentation, and textural changes.1

The Q-switched Nd-YAG lasers (with wavelengths of 532 nm or 1064 nm) have a large spot size, concentrated energy densities, high repetition rates, and greater beam diameter, allowing for rapid, effective treatment of closely clustered and deep tattoos.6 Five treatments of red or orange tattoos may achieve 75% clearance in about 60% of patients.1

The 1064-nm Nd:YAG laser, which has the deepest penetration and carries the least risk for hypopigmentation,1 is indicated for black and dark blue pigments. It is considered the ideal choice for tattoo removal in dark-skinned patients,14,16 since its longer wavelength represents a lower affinity for melanin.4 The 532-nm Nd:YAG laser is effective for removal of red, yellow, and orange pigments.6 Ten or more treatments may be required for 75% clearance of a professional tattoo.1

Some adverse effects of Nd:YAG laser use include whitening of the skin, with occasional mild pinpoint bleeding. Use of the 532-nm model is associated with purpura, resulting from hemoglobin absorption; this may last from one week to 10 days. The 1064-nm Nd:YAG laser is the least effective for removing bright-colored pigments.1,17

The Q-switched alexandrite laser is generally used to remove black, blue, and green pigments. Typically, four to 10 sessions are required at intervals of one to two months. Transient hypopigmentation, typically lasting three to four months, occurs in about half of patients, and textural changes have been reported in about 12%.6,8

The 510-nm, pulsed-dye Q-switched alexandrite laser is reportedly effective in removing red pigment.4

Complications, Adverse Effects, and Their Management
Although Q-switched lasers appear quite effective in tattoo removal, their use is not without adverse effects.

Hypopigmentation
The most common chronic adverse effect of laser treatment is hypopigmentation. The risk is high in dark-skinned patients undergoing treatment with the QSR or alexandrite lasers4 and increases in any patient according to the number of treatment sessions. Hypopigmentation occurs in more than 38% of patients treated with QSR lasers and typically lasts for two to six months.6

In a 2004 study, Gundogan et al18 attempted repigmentation with an excimer laser (Nd:YAG/potassium titanyl phosphate–Nd:YAG) in a patient with hypopigmentation following laser tattoo removal. Repigmentation required 40 treatment sessions over 15 months—not a cost-­effective option.6 A better solution might be to minimize the risk for hypopigmentation by use of picosecond lasers (see “Better Options on the Horizon?”, below).8

Hyperpigmentation
Hyperpigmentation can occur as a result of melanocytes’ increased melanin production in response to laser-generated heat. This effect is usually temporary, but recovery time varies.4 The risk of hyperpigmentation depends largely on skin type, with darker-skinned patients (ie, Fitzgerald type III or IV skin) at higher risk.6,19 Patients at risk for hyperpigmentation should avoid sun exposure before and after laser treatments; UVA/UVB sun blocks are essential if sun exposure cannot be avoided.1

Hyperpigmentation can also be treated with hydroquinone or fractional photothermolysis.6

Paradoxical Darkening of the Tattoo
Paradoxical darkening occurs when the chemical composition of the ink is changed by laser treatment—for example, from rust-colored ferric oxide to jet black ferrous oxide. Similarly, titanium dioxide contained in white ink that is used to brighten other colors can be reduced to titanium oxide or blue Ti3+ in response to laser therapy.1 Darkening is often difficult to correct, requiring the use of several lasers, including Q-switched or ablative (eg, ultrapulse CO2, pulsed erbium:YAG) lasers.9

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