Measuring the effects of topically applied skin optical clearing agents and modeling the effects and consequences for laser therapies.

摘要

Human skin prepared with an optical clearing agent manifests reduced scattering as a result of de-hydration andrefractive index matching. This has potentially large effects for laser therapies of several skin lesions such as port winestain, hair removal and tattoo removal. With most topically applied clearing agents the clearing effect is limited becausethey penetrate poorly through the intact superficial skin layer (stratum corneum). Agent application modi other thantopically are impractical and have limited the success of optical clearing in laser dermatology. In recent reports,however, a mixture of lipofylic and hydrofylic agents was shown to successfully penetrate through the intact stratumcorneum layer which has raised new interest in this field. Immediately after application, the optical clearing effect issuperficial and, as the agent diffuses through the skin, reduced scattering is manifested in deeper skin layers. Forpractical purposes as well as to maximize therapeutic success, it is important to quantify the reduced scattering as wellas the trans-cutaneous transport dynamics of the agent. We determined the time and tissue depth resolved effects ofoptically cleared skin by inserting a microscopic reflector array in the skin. Depth dependent light intensity wasmeasured by quantifying the signal of the reflector array with optical coherence tomography. A 1-dimensional massdiffusion model was used to estimate a trans-cutaneous transport diffusion constant for the clearing agent mixture. Theresults are used in Monte Carlo modeling to determine the optimal time of laser treatment after topical application ofthe optical clearing agent.