Characterization of Laser Tattoo Removal Treatment Using Pulsed Photothermal Radiometry

Matija Milanic, Boris Majaron
Pages: 68-74

Pulsed photothermal radiometry (PPTR) enables noninvasive determination of temperature depth profiles induced in strongly scattering biological tissues and organs, including human skin, by pulsed laser irradiation. In the present study, we evaluate the potential of this technique for objective characterization of a laser tattoo removal procedure.

The study involved 5 healthy volunteers (age 20-30 years) undergoing tattoo removal treatment using a Q-switched Nd:YAG laser. Four measurement and treatment sessions were performed over a time period of 10 months. Prior to each treatment, PPTR measurements were performed on several tattoo sites and one nearby healthy site in each patient, using a 5 μs Nd:YAG laser at low radiant exposure values and a dedicated PPTR setup. The laser-induced temperature profiles were reconstructed using a custom numerical optimization code. In addition, each tattoo site was documented with a digital camera and measured with a custom colorimetric system (in tristimulus color space), providing an objective evaluation of the therapeutic efficacy to be correlated with our PPTR results.

The laser-induced temperature rise in previously untreated tattoos was maximal at a subsurface depth of µ300 μm. In tattoo sites that responded well to laser therapy, a significant drop of the temperature peak was observed in the subsequent temperature depth profiles. In several sites which appeared much less responsive according to photography and the colorimetric record, a progressive shift of the laser-induced temperature profile deeper into the dermis was observed over the course of consecutive laser treatments, indicating that the tattoo removal procedure was nevertheless effective.

Keywords: laser tattoo removal, pulsed photothermal radiometry, temperature depth profiling, colorimetry

Article: J. LA&HA, Vol. 2013, No. 1; pp. 68-74.

Characterization of Laser Tattoo Removal Treatment Using Pulsed Photothermal Radiometry