On the inverse problem in transcutaneous bilirubinometry

Summary Transcutaneous bilirubinometry based on reflectance spectroscopy technique requires the development of suitable optical models of icteric skin and the solution of the inverse problem to derive pigment concentrations from spectral measurements. An algorithm is presented which allows the evaluation of bilirubin concentration during phototherapy. The present analysis shows that quantitative evaluation of bile pigment concentrations during phototherapy can be obtained with a good degree of accuracy by an inverse best-fit procedure; moreover, the knowledge of pigment kinetics makes this method almost independent of other conditions of the skin. The present results refer to the initial part of the phototherapy cycle and are based on a simple model of icteric skin; they may help to extend the application range of commercial transcutaneus bilirubinometer and to investigate the photoconfigurational transient of phototherapy.