Newer ruby lasers with a shorter pulse duration (approximately 25 ns), higher fluences (8-10 J/cm2), and better beam quality clear tattoos more rapidly. Lowe reported similar results by using 10 J/cm2 at 6- to 8-week intervals, and after 5 treatment sessions, reported that 22 of 28 professional tattoos showed excellent results (>75% improvement). A preliminary report by Levins et al was similar, with excellent results and minimal side effects.
Kilmer and Anderson initiated treatment at a fluence of 6-8 J/cm2 with a 40- to 80-nanosecond pulse width and reported black and green ink to be the most responsive, with other colors requiring significantly more treatments. Amateur tattoos usually required 4-6 treatment sessions, and professional tattoos usually required 6-10 sessions; however, in some patients as many as 20 treatment sessions were needed. They noted several trends: professional, distally located, recently acquired, or deeply placed tattoos may be difficult to remove, requiring more treatment sessions to completely eradicate them. Acceptable clearing varied greatly from patient to patient, with some individuals more accepting of vague residual pigment.
The QSRL is remarkably effective in removing tattoos with minimal scarring, although multiple treatment sessions are required. Hypopigmentation is common (occurring in >50% of patients), and although usually transient (2-6 mo), may be permanent. Transient hyperpigmentation is also common and seems to be related more to skin type than to laser treatment.
Scarring and textural changes rarely occur. The risk of adverse tissue response and the speed of clearing both appear to be fluence and pulse-width related, with higher fluences and shorter pulses more effective but causing more nonspecific tissue damage as well. High-energy short pulses cause a pressure shock wave that ruptures blood vessels and aerosolizes tissue with potentially infectious particles, requiring the use of a protective barrier or plastic tube to protect the operator. The use of larger spot sizes with lower fluences eliminates this problem to a large extent.
The occurrence of scarring or tissue textural changes has also been attributed to hot spots within the beam and pulse-to-pulse variability. The QSRL effectively removes black, blue-black, and green ink, although green ink can be difficult despite reflectance spectra predictions that it will respond at 694 nm. Other colors respond poorly to the QSRL. The laser has a repetitive rate of 1 pulse every 1-2 seconds, but no aiming beam to assist in proper alignment. Bleeding and tissue splatter can be cumbersome, but cone devices protect the operator from exposure.
Q-Switched Nd:YAG Laser
The Q-switched Nd:YAG laser was explored in anticipation that its longer wavelength (1064 nm) would increase dermal penetration and decrease melanin absorption, thus improving the response of QSRL-resistant tattoos and avoiding pigmentary changes. An initial report of 20 professional and 3 amateur tattoos in 4 treatment sessions showed the Nd:YAG laser equal to the QSRL in removal of blue-black tattoos at 6 J/cm2. Hypopigmentation and skin texture change were more common with the QSRL than with the Q-switched Nd:YAG laser. Green and red pigments were not removed with the 1064 nm Nd:YAG laser; however, some green pigment was removed with the QSRL.
The ability of the Q-switched Nd:YAG laser (1064 nm, 10 ns, 5 Hz) to remove pigment in QSRL-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 spot size. In most patients, more than 50% lightening of residual tattoo ink was noted with the first treatment, with the greatest improvement seen with higher fluences. Unfortunately, the higher fluences (12 J/cm2) and shorter pulses (10 ns) resulted in more tissue debris and bleeding. A plastic shield was required to promote laser operator safety.
Kilmer et al investigated both QSRL-resistant tattoos and untreated tattoos in a prospective, blinded, dose-response study by using the Q-switched Nd:YAG laser. Twenty-five professional tattoos and 14 amateur tattoos were treated in quadrants by using 6, 8, 10, and 12 J/cm2 and a 2.5-mm spot size. Four treatment sessions were performed at 3- to 4-week intervals. More than 75% ink removal was seen in 77% of black tattoos, and more than 95% ink removal was seen in 28% of tattoos (11 of 39 patients) treated at 10-12 J/cm2. No significant difference was seen in the response of previously untreated tattoos and QSRL-resistant tattoos.
Treatment at the highest fluence (12 J/cm2) proved more effective (P < .01) at removing black tattoo ink than 6 and 8 J/cm2. Green, yellow, white, and red inks resisted treatment and cleared 25% or less after 4 treatment sessions. Purple and orange inks responded minimally. Although textural changes were noted during the course of treatment, these cleared with time and only 2 of 39 tattoos were graded with trace textural changes present. No hypopigmentation and a single case of hyperpigmentation were noted. These results were similar to those reported by Ferguson and August.
Biopsy of treated tattoos revealed fragmentation of black ink particles up to 1.5 mm below the surface. Little, if any, fibrosis was seen in the superficial dermis. In addition, biopsy samples demonstrated that after clinical clearing of the tattoo, ink remained in the dermis, as reported with the QSRL.
Kilmer et al noted that despite increased bleeding and tissue splatter, the lack of both clinical scarring and histologic scarring is most likely attributable to the lack of thermal injury to collagen. The dermis and the 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 6 weeks or longer. The authors also noted a bright flash of white light from the tattoo during laser exposure, as mentioned with the QSRL. Because 1064-nm light is not visible, this flash must result from either a laser-induced plasma incandescence or an incandescence of tattoo ink particles. These both imply temperatures higher than 500°C.
The Q-switched Nd:YAG laser offers a great advantage for treating darker-skinned patients. Jones et al and Grevelink et al demonstrated effective tattoo removal with minimal hypopigmentation or hyperpigmentation. This outcome provides a significant benefit over the QSRL for darker-skinned patients in whom melanin absorption is a hindrance.
The Q-switched Nd:YAG laser is somewhat more effective in removing black ink, creating rare textural changes and almost no hypopigmentation. These improvements are attributable to the longer wavelength, higher fluence, and shorter pulse width. These same factors cause more bleeding and tissue splatter during treatment, making the treatment more cumbersome. The faster repetition rate (1-10 Hz) shortens the treatment session, although this is somewhat counterbalanced by the smaller beam size (4 mm vs 5-6.5 mm for the QSRL). Currently, larger spot sizes up to 6 mm are available with new, higher-powered Nd:YAG laser systems, which also enable deeper penetration and more effective treatment of deeper, denser tattoos. Better beam profiles minimize epidermal damage and decrease bleeding, tissue splatter, and transient textural changes. Often, little wound care is needed.
The primary disadvantage of the 1064-nm wavelength is the limited color range, which is basically restricted to black and dark blue/black tattoo pigment. However, a frequency-doubling crystal is a feature of this laser, which provides a 532-nm wavelength to effectively treat red ink. More than 75% removal of red ink was reported with 3 treatment sessions; orange ink and some purple inks respond almost as well. However, yellow ink responds poorly, presumably because of its dramatic decrease in absorbance from 510-520 nm.
Because of the laser's 1064-nm wavelength absorbance by melanin and hemoglobin, blistering and purpura frequently occur.