This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Once practiced by a small portion of society, skin tattooing has become more common place. A recent survey suggests that 1 in 4 Americans has at least one tattoo. Following this growth in the practice of tattooing has been an increase in demand for laser tattoo removal. The same survey estimated that 17% of those with a tattoo had considered removing it. The gold standard procedure for laser tattoo removal involves the use of one of four, or a combination of, Q-switched lasers operating at wavelengths of 532nm, 694nm, 755nm, and 1064nm. While laser tattoo removal has been effective, it is often an expensive and time consuming process. Amateur tattoos often require four to six sessions to affect near complete erasure. Professional tattoos, which use more robust pigments and are generally placed at higher concentrations in the dermis, require an average of 8-12 treatments. In both cases treatments need to be spaced over four to six weeks. Complications include skin scaling or blistering due to excessive absorption of laser energy by the surrounding tissue, hypo and hyper pigmentation, and spontaneous tattoo darkening due to the presence of titanium oxide or ferric oxide. Ideally, treatment must remove the tattoo with the fewest number of treatments while minimizing these complications. Currently laser selection, as well as other parameters such as fluence, is chosen by the clinician based on qualitative observation and previous clinical experience. The majority of literature involving laser tattoo removal effectiveness has been based on clinical case studies of treatments;however, tattoo related optical information could be used to improve the efficiency of the treatment. In the mid 1990s, Haedersdal et al. measured the spectral reflectance of tattooed skin from 300nm to 800nm to establish ranges of maximum absorption for several colors. Thirteen tattoos involving fourteen different colors, the most common being red and green, were included in the study. The authors suggested that spectral reflectance information could be used to guide laser selection including the use of tunable solid state lasers for tattoo removal. Baumler et al used a spectrophotometer over the wavelength 320nm to 1100nm to measure the absorption spectra of a large number of commercially available pigments suspended in solvent. Unfortunately this is not a practical method for guiding laser tattoo removal because of the even larger number of dyes available. Colors in a tattoo are often a combination of pigments chosen by and known only to the original tattoo artist. Also, bench top spectroscopy does not provide information such as a reduced scattering coefficient or the optical properties of the underlying skin. Most recently, O??""""""""goshi et al used confocal scanning laser microscopy to visualize the particle size and density of a tattoo. This technology scans at a single wavelength and cannot provide rapid wide-field mapping of spectral properties. In this project we meausure absorption and scattering spectra for tattoos using Modulated Imaging, a new wide-field spectral imaging modality.
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