Optimal tattoo removal in a single laser session based on the method of repeated exposures

Background

Unwanted tattoos are treated with Q-switched lasers. Despite a series of treatments, efficacy is limited.

Objective

We compared a single Q-switched laser treatment pass with 4 treatment passes separated by 20 minutes.

Methods

Eighteen tattoos on 12 adults were divided in half and randomized. One half received a single treatment pass (the “conventional” method) with a Q-switched alexandrite laser (5.5 J/cm², 755 nm, 100-nanosecond pulse duration, 3-mm spot size), and the other half received 4 treatment passes with an interval of 20 minutes between passes (the “R20” method). Tattoo lightening was compared 3 months later, by blinded evaluation of photographs. Biopsy specimens obtained before and immediately after treatment on both halves were also compared in blinded fashion.

Results

Immediate whitening reaction occurred on the first treatment pass, with little or no whitening on subsequent passes. Three months later, treatment with the R20 method was much more effective than conventional single-pass laser treatment (P <.01; all tattoos favored the R20 method). Despite greater epidermal injury with the R20 method, neither method caused adverse events or scarring. Light microscopy showed greater dispersion of tattoo ink with the R20 method.

Limitations

This prospective study involved a small number of subjects.

Conclusions

The R20 method is much more effective than conventional laser tattoo treatment, removing most tattoos in a single treatment session. New laser device technology is not required to practice this method.

Introduction

Q-switched lasers emitting short, high-intensity pulses are widely used for treatment of unwanted tattoos based on the principles of selective photothermolysis.1, 2, 3, 4, 5, 6

Multiple treatment sessions (4-6 for amateur tattoos and up to 20 for professional tattoos) are usually necessary to obtain acceptable tattoo lightening.7, 8, 9, 10 The number of treatment sessions depends on pigment color, composition, density, depth, duration, body location, and the number of tattoo inks present. Each successive treatment removes some of the remaining pigment.7, 8, 11 Laser treatment fragments the tattoo ink particles, which are then cleared or rephagocytosed into smaller aggregations to the point where the tattoo is no longer clinically apparent.5, 12, 13, 14 Laser treatments are typically spaced 1 to 2 months apart.4, 7, 15 The overall treatment course is often prolonged, costly, and sometimes impractical, which can lead to patient dissatisfaction and abandonment of the treatment.2, 9, 11, 16 Risks of treatment include scarring,² permanent hypopigmentation,15, 16 and the possibility of incomplete tattoo removal.¹³ For these reasons, laser tattoo removal frustrates patients and challenges clinicians.

In a preliminary animal (swine) study, we compared the efficacy of tattoo removal by using a wide range of pulse durations and treatment conditions. A surprising result was that administration of multiple laser exposures delivered after fading of the immediate whitening reaction was more effective than a single laser exposure. Immediate whitening is a common reaction to Q-switched laser treatment due to bubbles that form in the dermis. The immediate whitening reaction fades over about 20 minutes, as the gas bubbles dissolve. We decided to compare the efficacy of Q-switched laser tattoo removal in a single pass versus treatment in multiple passes with a 20-minute interval between them. The cumulative effect of two consecutive pulses delivered one immediately after another has been previously examined and appeared to offer only slightly greater efficacy.¹⁷ The administration of two pulses separated by 30 seconds to 20 minutes has also been tested and was not more effective than one pulse.⁶ We hypothesized that the temporary increase in optical scattering due to immediate whitening reaction⁴ limits penetration and efficacy of laser treatment, such that a second exposure performed before fading of the immediate whitening reaction did not substantially improve efficacy.