Different volume fraction of absorbing and scattering agents producing similar spectral reflectance in agarose-gel skin phantom

摘要

Spectral measurement of human skin has often been used to provideknowledge about skin conditions and sometimes physical conditionmainly by analyzing spectral reflectance curve. Such analysis generatesinformation about skin parameters, largely about absorption coefficientμ_a and scattering coefficient μ_s. Now, these μ_a and μ_s are used to evaluatepigments concentration (melanin and hemoglobin) and tissuemorphological information. However, such an evaluation of μ_a and μs byreflectance spectra goes through unpredictability as some different valuesof μ_a and μs produce similar spectra. In thisstudy, we investigate the phenomena of similarspectra from different μ_a and μ_s in 3-layeredagarose-gel phantom and finally we confirmthose divergent μ_a and μ_s values of phantomsby inverse Monte Carlo (IMC) method.A three-layered agarose-gel phantom wasused to emulate the human-skincharacteristics. Each of the three layers hasspecific thickness, they are: layer 1(epidermis)-0.06cm, layer 2 (dermis)–0.68cmand layer 3 (subcutaneous)-0.45cm. Asabsorbing agents, coffee solution in layer 1,and horse blood with 44% hematocrit in layers2 and 3 are used. For scattering agent, 20%intralipos solution in different volume fractionin layers 1, 2 and 3 is used. Also, agar solutionis used as the binding agent in each layer. Tofind out the actual μ_a and μs values of thephantoms having different volume fraction ofabsorbing and scattering agents IMC wasemployed, in which layer-wise reflectance andtransmittance were used as inputs and asoutput, it resulted in generating μ_a and μsvalues of each layers respectively.