Early on, patients were treated every 4 weeks. In the alexandrite study, of the 4 patients unable to return for their scheduled treatment, 2 patients went 3 months and 2 patients went 5 months between treatments. Two of these 4 patients reported progressive and gradual clearing of the tattoo during the prolonged interval between treatment sessions; the other 2 patients noticed immediate improvement only, which then stabilized without further clearing.
The appropriate treatment interval is critical and yet poorly understood. To study different treatment intervals, one group of patients received 3 treatments within 7-10 days and then no treatment for 3 months, a second group had single treatments at 2-month intervals, and the third group had single treatments at 1-month intervals. No difference in the rate of tattoo clearing was seen. All 3 treatment intervals resulted in approximately 50% clearing after 3 treatment sessions; however, as the number of treatments increases, the potential for tissue reaction also increases.
Occasional rest periods or longer treatment intervals of 2-3 months allow melanin to recover and transient textural changes to normalize, which may help avoid unwanted adverse tissue responses. Higher fluences and shorter pulse widths appear to remove tattoo pigment more rapidly but may induce excessive shock wave tissue reaction; therefore, they must be balanced with the desire to remove pigment without scarring or hypopigmentation. The current recommendation is to treat at 6- to 8-week intervals unless a longer period is needed for tissue recovery.
Recommended Treatment Parameters
The main parameters include pulse duration, wavelength, fluence, and spot size. All of the Q-switched lasers are in the nanosecond range, and pulse width is predetermined by the laser. Wavelength is chosen based on the best available wavelength for the tattoo ink color. For example, red ink is best treated by a green wavelength (510 or 532 nm), and green ink is best treated by a red wavelength (694 or 755 nm). When melanin is present, the 1064-nm wavelength is the best choice to avoid disruption of the epidermis.
Fluence should be sufficient to produce immediate whitening without immediate bleeding or blistering. Larger spot sizes provide deeper penetration and should be used as long as sufficient fluence can be obtained. This maximizes the distribution of laser light to the dermal pigment and minimizes cutaneous injury. Predicting the number of treatment sessions necessary for tattoo removal is difficult.
Frequently, the initial treatment session produces a more dramatic response than subsequent sessions. Definite sites of clearing, corresponding to laser impacts, are often seen. Other tattoos are highly unresponsive during early treatment phases, although biopsy samples reveal fragmentation of tattoo granules. The response difference from one patient to another likely involves the efficiency of mobile macrophages in removing fragmented tattoo pigment debris, as well as the density and amount of tattoo pigment present. The speed of the macrophage response, as well as the maximum amount of pigment removed per session, likely varies from patient to patient and, to some extent, from treatment to treatment. The more superficial the tattoo pigment and the less the total volume of pigment, the fewer the number of treatments necessary to remove the pigment.
In contrast to anecdotal reports about the QSRL and the Nd:YAG laser, new Q-switched alexandrite-treated tattoos clear faster, possibly because the location of newer tattoos is more superficial. New tattoos have sharp lines with bright colors; whereas, older tattoos are blurred, with indistinct lines and duller, bluer colors, presumably resulting from ink movement deeper into the dermis. Further studies are underway to explore these observations.