STUDY Comparison of Responses of Tattoos to Picosecond and Nanosecond Q-Switched Neodymium:YAG Lasers CDR E. Victor Ross, USN; George Naseef, MD; Charles Lin, PhD; Michael Kelly, MS; Norm Michaud, MS; Thomas J. Flotte, MD; Jill Raythen; R. Rox Anderson, MD Objective: To test the hypothesis that picosecond la- ated with the study (and blinded to the treatment type) ser pulses are more effective than nanosecond domain evaluated photographs to assess tattoo lightening. For- pulses in clearing of tattoos. malin-fixed specimens were examined for qualitative epi- dermal and dermal changes as well as depth of pigment Design: Intratattoo comparison trial of 2 laser treat- alteration. Electron micrographs were examined for par- ment modalities. ticle electron density and size changes (in vivo and in vitro). The gross in vitro optical density changes were Setting: A large interdisciplinary biomedical laser labo- measured. ratory on the campus of a tertiary medical center. Results: In 12 of 16 tattoos, there was significant light- Patients: Consecutive patients with black tattoos were ening in the picosecond-treated areas compared with enrolled; all 16 patients completed the study. those treated with nanosecond pulses. Mean depth of pigment alteration was greater for picosecond pulses, Intervention: We treated designated parts of the same but the difference was not significant. In vivo biopsy tattoo with 35-picosecond and 10-nanosecond pulses from specimens showed similar electron-lucent changes for 2 neodymium:YAG lasers. Patients received a total of 4 both pulse durations. In vitro results were similar for treatments at 4-week intervals. All laser pulse param- both pulse durations, showing increases in particle sizes eters were held constant except pulse duration. Radia- and decreased electron density as well as gross ink tion exposure was 0.65 J/cm2 at the skin surface. Biop- lightening. sies were performed for routine microscopic and electron microscopic analysis at the initial treatment session and Conclusions: Picosecond pulses are more efficient than 4 weeks after the final treatment in 8 consenting pa- nanosecond pulses in clearing black tattoos. Black tat- tients. Also, ink samples were irradiated in vitro. toos clear principally by laser-induced changes in the in- trinsic optical properties of the ink. Main Outcome Measures: In vivo, on the comple- tion of treatment, a panel of dermatologists not associ- Arch Dermatol. 1998;134:167-171 -SWITCHED LASERS have pulses.5 Assuming a thermal or mechanical revolutionized the treat- mechanism for tattoo removal, subnanosec- ment of tattoos. By restrict- ond pulses theoretically should be more ef- ing pulse duration, ink par- fective in tattoo treatment. To test the hy- ticles reach very high tem- pothesis that picosecond pulses are more ef- Q peratures1 with relative ficient than nanosecond pulses in the sparing of adjacent normal skin. This signifi- treatment of tattoos, we compared tattoo cantly decreases the scarring that often re- clearing after treatment with 2 neodymium: sults after nonselective tattoo removal meth- YAG laser systems in which all laser param- ods, such as dermabrasion or treatment with eters were held constant except pulse dura- a carbon dioxide laser. The Q-switched neo- tion. Using both pulse widths, we also ex- dymium:YAGlaserhasbeenshowntobepar- amined immediate particle responses to ticularly effective in the treatment of black pulsed laser irradiation in vitro. From the Department of tattoos.2,3 Neodymium:YAG lasers in clini- Dermatology, Wellman cal use are capable of delivering 10-nano- RESULTS Laboratories of Photomedicine, second pulses. The most common pigment Harvard Medical School, particle, carbon black in india ink, has been Of the 16 tattoos, 12 were judged to clear bet- Massachusetts General 4 Hospital, Boston, Mass. Dr Ross showntobeabout40nmindiameter. These ter with picosecond pulses based on the re- is now with the Department of particleshavethermalrelaxationtimesofless sponse of black ink regions (Figure 1 shows Dermatology, Naval Medical than10nanoseconds;therefore,anargument a representative result). In the remainder of Center, San Diego, Calif. can be made for using subnanosecond tattoos, there was only slight or no clearing ARCH DERMATOL / VOL 134, FEB 1998 167 ©1998 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 10/02/2021 PATIENTS, MATERIALS, AND conventionally used in clinical practice (fluence of 8.0 J/cm2 and 2.5-mm spot size). Both laser units used an articulated METHODS arm and focusing handpiece lens assembly for beam deliv- ery. Care was taken to avoid gross overlapping of adjacent Sixteen patients with cosmetic tattoos participated after be- exposure sites. For all treatment sites, the patients under- ing informed of the nature of the protocol and giving con- went 4 treatments in the described manner at 3- to 4-week sent. The protocol was approved by the Subcommittee for intervals. All pulse energies were verified with an energy me- Human Subjects of the Massachusetts General Hospital, Bos- ter (Model 365, Scientech, Boulder, Colo) prior to each treat- ton. Patients were enrolled on a consecutive basis as long as ment. The beam profiles and spot sizes were determined by their tattoos were partly black and previously untreated. The imaging the beam with a charge-coupled device camera restriction to black tattoos allowed for a reasonable chance (Model TM-34KC, Pulnix, Sunnydale, Calif) as follows. A for pigment lightening, given the response of black tattoos black surface was placed at the object distance in front of to 1064-nm radiation and the low fluences used in the study the articulated arm. The surface was brought into the focus (vide supra), and easier correlation between clinical re- of the camera so that the laser spot was in the field of view. sponses and in vitro black pigment alterations induced by la- The video signal was input into a frame grabber (CX100, Im- ser. Of the 16 tattoos, 15 were created by a professional and age Nation Corp, Beaverton, Ore) interfaced with a per- 1 was done by an amateur. Eleven of the tattoos were mul- sonal computer. After capturing the image, the beam size and ticolored, most of these containing black, red, and green pig- profile were determined with the aid of imaging software (NIH ments. The remaining 5 clinically showed only black pig- Image, National Institutes of Health, Bethesda, Md). mentation. Tattoos were divided into 3 parts, the first 2 parts Photographs were taken before each treatment. All pho- being the treatment sites for comparison between pulse du- tographs were taken with the same 35-mm camera (AE1, rations. These sites were designated either as the left or right Canon USA, Lake Success, NY) under similar lighting con- symmetrical parts of a representative portion of the whole tat- ditions. The same film type (Ektachrome 100, Kodak, Roch- too. Part 1 was treated with a mode-locked Q-switched neo- ester, NY) and processing method were used for all pho- dymium:YAG laser (Model YG501, Quantel Technologies, tographs. Local anesthesia (2% lidocaine with epinephrine) Santa Clara, Calif) delivering 35-picosecond pulses. Spot size, was used in patients requesting it. In 10 consenting pa- fluence, and repetition rate were 1.4 mm, 0.65 J/cm2, and 10 tients, 2-mm punch biopsy specimens were obtained be- Hz, respectively. The beam profile was gaussian. Part 2 was fore and immediately after the first treatment, and at 30 days treated with a Q-switched neodymium:YAG laser (Model after the final treatment. Samples were taken from tattoo NY82-10, Continuum, Santa Clara, Calif). Laser parameters areas that appeared clinically black. Specimens were fixed were identical to part 1 except for pulse duration, which was in 10% buffered formalin, processed in paraffin, and stained 10 nanoseconds, and the beam profile, which was multimo- with hematoxylin and eosin. Also, 1-µm sections were cut dal. The remainder of the tattoo was treated with the same and stained with buffered 0.5% toluidine blue O. These sec- laser values as those for part 2 except with parameters tions and their unstained counterparts were examined for with either pulse duration (Table). Within individual tat- irregularly shaped “clumps” that ranged from 1 to 5 µm in toos, black tattoo regions responded best in all cases. Over- diameter. In some specimens, occasional distinct red and all, clearance of black ink was better after picosecond treat- green granules (1-2 µm in diameter) were identified. Inter- ment (P,.002). Although green tattoo regions lightened in tattoo ink depth varied considerably and ranged from 250 somepatients,red,purple,blue,orange,andyellowpigments to 1700 µm deep to the stratum corneum. Intratattoo ink did not clear regardless of number of treatments or pulse du- depths, however, were more consistent, with biopsy speci- ration, and overall, nonblack tattoo regions responded simi- mens showing no more than ±200 µm depth variability from larly for both pulse durations (P..20). Although not for- different sections of the same specimens. Immediately af- mally assessed by the panel of raters, we found that conven- ter treatment, nonblack particles appeared unaltered in the tional high-energy nanosecond pulses produced clearing biopsy specimens; however, in all cases there was a smudg- comparable with that of the lower-energy picosecond pulses. ing of black particles, noted as a transition from black gran- During treatment, picosecond pulses produced more intense ules to amorphous light brown bodies with a lacy appear- immediate whitening than low-energy nanosecond pulses. ance. In general, a line could be drawn demarcating the depth Also, in most cases, picosecond pulse sites showed plasma of transition of the particles. This depth ranged from a mean formation and slight postoperative pinpoint bleeding not ob- (±SEM) of 670±96 µm (n=10) for picosecond pulses to served after nanosecond pulses of the same fluence (Figure 590±107µmfornanosecondpulses.Otherimmediatechanges 1).