Three types of Q-switched pulsed lasers can remove that now-undesirable body art
Tattooing is an ancient art whose origins have been traced to the Stone Age (12,000 bce). Primitive humans slashed their skin during bereavement ceremonies and rubbed ash into the cuts as a sign of grief. Decorative tattooing has been traced to the Bronze Age (8000 bce) by the circumstantial evidence of crude needles and pigment bowls found in caves in France, Spain, and Portugal. Bronze Age humans decorated animal skins worn for warmth with ochre and plant pigments. This may have led to decorative tattooing of their own skin, because mummies dating from 4000 bce had crude tattoos. Tattooing also thrived throughout ancient China, Japan, and North Africa—areas isolated by geography and absence of communication—suggesting that tattooing represents a response to some inherent human need.
Attempts at tattoo removal may also have begun about 6,000 years ago, based on evidence found on Egyptian mummies. The motivation for tattoo removal may be not only internal regret and the desire for more mature identity and self-expression, but may also be driven by societal pressure. Tattoos may become a significant barrier to employment, social status, or religious acceptance. In general, tattoos are not well-received by the general public, and tattooed individuals may be perceived as antisocial, aggressive, immature, or unable to accept controls and authority.
Over the centuries, many different tattoo-removal methods have been explored. The earliest documented report of tattoo removal was by Aetius, a Greek physician, who described salabrasion in 543 ce. Older tattoo-removal techniques involve the destruction or removal of the outer skin layers by mechanical, chemical, or thermal means, accompanied by inflammation. The primary disadvantage of these mechanical destructive modalities is the high risk of scarring. Hypertrophic scars are very common when tissue removal is performed deeply in an attempt to remove all tattoo pigment. In addition, residual pigment is common, and postoperative pain can be significant.
Surgical excision of skin containing tattoo pigment is also common, but it often results in incomplete tattoo removal, tissue distortion, and scarring because of limitations in wound closure and healing. It was not until the laser was developed for medical uses that tattoos could be removed effectively and nondestructively.
Pulsed Laser Treatments
Anderson and Parrish’s principle of selective photothermolysis revolutionized the treatment of tattoos.1 They proposed that if a wavelength was well-absorbed by the target and the pulse width was equal to or shorter than the target’s thermal relaxation time, the heat generated would be confined to the target. Laser wavelength and pulse duration must be appropriately chosen to target tattoos specifically.
In one of the earliest studies, Diette et al2 examined the effects of a tunable dye laser at three wavelengths (505, 577, and 680 nanometers [nm]) using a 1-microsecond pulse to remove black, blue, red, and white tattoo pigment. They found that the threshold dose to induce histological changes was much less than that required for the argon laser, and that each wavelength reacted only with complementary colors of tattoo pigment. However, despite the short pulse time, widespread tissue necrosis was observed, and tattoo lightening occurred only as a result of significant dermal necrosis and resultant fibrosis. The authors postulated that an even shorter pulse—in the nanosecond domain—would interact best with the thermal relaxation time of the micrometer-sized pigment granule.
Q-switched ruby laser. The earliest reports of tattoo–pigment interactions with short-pulsed lasers were from Goldman et al in 1965.3,4 They compared the reaction of a dark blue tattoo with a nanosecond-pulsed Q-switched ruby laser with the corresponding reaction with a microsecond-pulsed ruby laser. They found nonspecific thermal necrosis with the microsecond impacts, whereas nanosecond impacts produced only transient edema, accompanied by a peculiar whitening of the impact area that lasted about 30 minutes. No thermal necrosis was present, but tattoo fragments remained in the dermis.
Other investigators confirmed and expanded these results by using a Q-switched ruby laser (694 nm, 20 nanoseconds) to remove blue and black tattoo pigments successfully without tissue damage.5,6 Biopsies performed after 3 months showed the absence of tattoo pigment and no evidence of thermal damage. These effects were dose-dependent, with fluences of 5.6 joules per square centimeter (J/cm2) or less showing the absence of thermal damage but incomplete pigment removal. Higher fluences led to subepidermal blisters, similar to second-degree burns, and dermal fibrosis at 3 months, but pigment removal was more complete.
Reid and coworkers continued the study of the Q-switched ruby laser, and in 1983 they published a report on the removal of black pigment in professional- and amateur-applied tattoos.7 They reported good results, particularly with amateur tattoos, but noted several disadvantages, including the need for multiple treatments, often six or more, for complete pigment removal. They also reported scarring in two patients, and emphasized the need to use relatively low powers (but above the threshold to produce immediate tissue whitening) and the importance of the treatment interval.
At least 3 weeks between treatments was necessary for tissue healing and pigment removal by macrophages. In vitro tests revealed an immediate reaction with ink that could be explained only as a chemical reaction. Biopsy specimens revealed evidence of the fragmentation of ink into smaller particles, which were then phago-cytized by macrophages. These two phenomena correspond with clinical observations of an immediate reduction in pigment during the first week after treatment, followed by gradual fading over the next several weeks without further therapy.
Newer ruby lasers with shorter pulse durations (approximately 25 nanoseconds), higher fluences (8–10 J/cm2), and better beam quality clear tattoos more rapidly.8,9 Lowe et al reported similar results using 10 J/cm2 at 6–8-week intervals; after five treatments, they reported excellent results (greater than 75% improvement) on 22 of 28 professional tattoos.10 Levins and coworkers’ preliminary report was similar, with excellent results and minimal side effects.11 In addition to amateur and professional tattoos, cosmetic, iatrogenic, traumatic, and mucosal amalgam tattoos have been removed without scarring by using Q-switched ruby lasers.12–15 See Figure 1 for an example of our treatment with this laser.
Q-switched Nd:YAG laser. The neodymium laser was explored in anticipation that its longer wavelength (1064 nm) would increase dermal penetration and decrease melanin absorption, improving the response of ruby laser–resistant tattoos and avoiding pigment changes. An initial report of 20 professional and 3 amateur tattoos in four treatment sessions showed that the Nd:YAG laser equaled the ruby laser in removing blue-black tattoos at 6 J/cm2. Hypopigmentation and changes in skin texture were more common with the ruby laser. Green and red pigments were not removed with the Nd:YAG laser, whereas some green pigment was removed with the ruby laser.16
The ability of the Nd:YAG laser (1064nm, 10 nanoseconds, 5 hertz [Hz]) to remove pigment in ruby laser–resistant tattoos was assessed in the treatment of 28 tattoos (23 professional, 5 amateur) using fluences of 6–12 J/cm2 with a 2.5-mm-diameter spot size.17 In most cases, more than 50% lightening of residual tattoo ink occurred with the first treatment, with the greatest improvement seen with higher fluences. Unfortunately, the higher fluences (12 J/cm2) and shorter pulses (10 nanoseconds) resulted in more tissue debris and bleeding, necessitating the use of a plastic shield or transparent membrane to ensure the safety of the laser operator.18
Kilmer et al noted that the lack of scarring, despite the increased bleeding and tissue splatter, is most likely due to the lack of thermal injury to collagen.19 The dermis and epidermis sustain mechanical injury from the photoacoustic wave, but this trauma is apparently highly reparable. Textural changes generally resolve within 4–6 weeks, suggesting an optimal treatment interval of 6weeks or longer.
The Q-switched Nd:YAG laser has a great advantage for treating darker-skinned patients. Jones et al and Grevelink et al demonstrated effective tattoo removal with minimal hypopigmentation and hyperpigmentation.20,21 This provides a significant benefit over the Q-switched ruby laser for darker-skinned patients in whom melanin absorption is a hindrance, and for cosmetic eyeliner tattoos, where care must be taken not to damage the eyelashes or retinal melanin.22 In addition, the smaller spot size available with most Q-switched Nd:YAG lasers (1.5-mm diameter) allows for more accurate distinguishing of the tattoo in sensitive areas.
The primary disadvantage of the 1064-nm wavelength is its limited color range, which is restricted to black and dark blue-black tattoo pigments. However, this laser has a frequency-doubling crystal that allows the use of the 532-nm wavelength to treat red ink effectively. Removal of more than 75% of red ink in three treatment sessions has been reported, and orange and some purples respond almost as well. However, yellow ink responds poorly, presumably because of its dramatic drop in absorbance between 510 and 520 nm, as do green and blue inks, whose absorption peaks at 600 nm or longer.23 Another disadvantage of 1064-nm light is that it is absorbed by melanin and hemoglobin, frequently causing blistering and purpura.
Q-switched alexandrite laser. The third Q-switched laser developed for tattoo treatment, the alexandrite laser, has a wavelength of 755 nm, a pulse width of 100 nanoseconds (50 nanoseconds is available in newer models), and a repetition rate of 1 Hz.24–27 The 3-mm-diameter beam is delivered via a fiber-optic system or an articulated arm. Reflectance studies at 755 nm suggest excellent absorption by black pigments, good absorption by blue and green, and poor absorption by red, as confirmed by preliminary studies performed on tattooed guinea pigs and harvested human skin.28 This result corroborates previous findings from preliminary trials on Yucatan mini-pigs, in which one treatment session provided excellent results for removing black ink, good results for blue and green, and poor results for red. Efficacy was relate to fluence; it was greatest at 8 J/cm2 and decreased monotonically with decreasing fluence until there was no effect at 2 J/cm2.29
The first human study using the Q-switched alexandrite laser involved 30 tattoos and fluences of 4.5–8.0 J/cm2. Test sites using three fluences of up to 6 J/cm2 were evaluated at 4weeks. The appropriate fluence was then selected, and the treatment was begun. A second test was done if none of the first set of fluences produced significant lightening. Fluences of 6 J/cm2 or higher were used once the tattoo had lightened by 20–50%.
Approximately 25% clearing of tattooed pigment required an average of 1.7 treatments; 50% clearing, 2.8 treatments; 75% clearing, 5.0 treatments; 90% clearing, 6.4 treatments; and complete clearing, 10.4 treatments (with a range of 4–16). Professional, cosmetic, traumatic, amalgam, and amateur tattoos were all cleared. The latter responded more rapidly, and required approximately three fewer treatments than the others, to reach complete clearance; some professional tattoos responded rapidly as well.30–35
Transient hypopigmentation is common (50% of patients), but often it is not apparent until after five to seven treatment sessions, and it usually resolves gradually over 1–12 months. As with the other Q-switched lasers, hyperpigmentation is dependent on skin type and clears with hydroquinone and sunscreen. Transient-surface textural changes have been noted in about 10% of patients. However, they all resolved within 3–9 months, although one patient developed a small scar (2 mm ¥ 7 mm) secondary to excoriating a treated area. See Figure 2 (page 42) for an example of our treatment with the alexandrite laser.
Following Q-switched laser treatment, immediate tattoo-ink darkening has been observed. Although this can occur with any color of ink, it is more common with red, white, and flesh-toned inks; darkening of yellow ink has also been reported.36 This is of particular concern with cosmetic tattoos.
Under certain circumstances, the potential for tattoo-ink darkening by treatment with Q-switched laser can be used to therapeutic advantage. One patient of ours who had auburn hair in her youth received red-brown eyebrow tattoos at age 30. Although she had been pleased with the tattoos for nearly 2 decades, her hair color grayed over time, and at age 55 she presented for tattoo treatment. Understanding the potential for red tattoos to turn black with Q-switched lasers, we used the ruby laser to achieve our patient’s desire to change the tattoo color from red to gray to match the change in her hair color (see Figure 3).
Laser treatment of flesh-tone, pink, red, and brown tattoos must be approached with caution. The resulting gray-black or other color change of the tattoo may be difficult to remove and is certainly more visible than the original cosmetic tone; therefore test sites are recommended.37–40
Current and Future Developments
Q-switched lasers provide a dramatic improvement over previous modalities for tattoo removal, and scarless removal has become the expected therapeutic outcome. Appropriate wavelength choice will facilitate clearing of multicolored tattoos, and current goals include more efficient specific targeting of tattoo pigment over a smaller number of treatment sessions. Exploration into the use of picosecond lasers is under way and may further enhance our ability to remove tattoos rapidly without damaging surrounding tissue.
Michelle Ehrlich, MD, is a Board-certified dermatologist and fellowship-trained cosmetic surgeon practicing in La Jolla, Calif. She can be reached at mehrlich@alumni. princeton.edu.
Mitchel P. Goldman, MD, is an internationally respected dermatologist and cosmetic surgeon. He is the founder and medical director of La Jolla Spa MD.
This article was adapted from Ehrlich’s chapter “Treatment of Tattoos” in the forthcoming textbook Cutaneous and Cosmetic Laser Surgery, edited by Goldman (Elsevier, 2006).
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