Laser und Medizin Technology

Berlin, Germany

Laser und Medizin Technology

Berlin, Germany
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Andree S.,Laser und Medizin Technology | Helfmann J.,Laser und Medizin Technology | Gersonde I.,Laser und Medizin Technology
Optics InfoBase Conference Papers | Year: 2011

Chromophore concentrations from skin contain information about the blood parameters, for example total hemoglobin content or antioxidant status of the skin. Deviations from the normal values of the concentrations may indicate pathologies. As the chromophore concentrations are determined from skin absorption coefficients, the optical absorption spectra of the isolated skin chromophores have to be known in advance, enabling least squares fitting of the basis spectra to the skin absorption coefficient. It could be shown that spectrally and spatially resolved reflectance in combination with a determination of absorption and reduced scattering coefficients from a look-up table provides a means for quantification of chromophores, although the accuracy largely depends on the tissue model. Good qualitative results can also be obtained with the homogenous tissue model used here. For example, it could be shown that the hemoglobin basis spectra determined from human whole blood and the pure water absorption fit very well to the skin absorption coefficients, but the ex vivo carotene spectra does not. Therefore it was examined how the carotene spectra change from ex vivo to in vivo. Interindividual and interpositional variation of the optical parameters could also be evaluated using this method as well as the dependence of determined optical parameters on the source-detector separation. © 2011 SPIE-OSA.


Andree S.,TU Berlin | Reble C.,TU Berlin | Helfmann J.,Laser und Medizin Technology | Gersonde I.,Laser und Medizin Technology | Illing G.,Laser und Medizin Technology
Journal of Biomedical Optics | Year: 2010

We present a new variant of a noncontact, oblique incidence spatially resolved reflectance setup. The continuously variable source detector separation enables adaptation to high and low albedo samples. Absorption (μa) and reduced scattering coefficients (μ′s) are determined in the wavelength range of 400-1000 nm using a lookup table, calculated by a Monte Carlo simulation of the light transport. The method is characterized by an silicone phantom study covering a wide parameter range 0.01 mm-1 ≤ μa ≤ 2.5 mm-1 and 0.2 mm -1 ≤ μ′s ≤ 10 mm-1, which includes the optical parameters of tissue in the visible and near infrared. The influence of the incident angle and the detection aperture on the simulated remission was examined. Using perpendicular incidence and 90-deg detection aperture in the Monte Carlo simulation in contrast to the experimental situation with 30-deg incidence and 4.6-deg detection aperture is shown to be valid for the parameter range μ′s > 1 mm-1 and μa ≤ 1.2 mm -1. A Mie calculation is presented, showing that a decreasing reduced scattering coefficient for increasing absorption can be the consequence of real physics instead of cross talk. © 2010 Society of Photo-Optical Instrumentation Engineers.


Friebel M.,Laser und Medizin Technology | Pernell O.,Laser und Medizin Technology | Cappius H.-J.,Laser und Medizin Technology | Helfmann J.,Laser und Medizin Technology | Meinke M.C.,Charité - Medical University of Berlin
Dental Materials | Year: 2012

Objectives: Esthetic restorations require that dental restorative materials have similar optical properties to teeth. To improve the color perception, the inhomogeneous morphology of the native tooth can be imitated by layering two optically different restorative materials. However until now the benefit of this method has not been satisfactorily demonstrated. Methods: The optical parameters, absorption coefficient μ a, scattering coefficient μ s, anisotropy factor g and effective scattering coefficient μ′s, were determined for the enamel and dentin material of the restorative material systems Artemis ® and Herculite XRV ®. This was carried out for each material system in the wavelength range between 400 and 700 nm using integrating sphere measurements followed by inverse Monte Carlo simulations. Results: Using the optical parameters and a forward Monte Carlo simulation, the color perception of layered samples could be predicted with a sufficient degree of accuracy. The total color impression was shown to be dependent on the sample thickness and the transparency/translucency of the single layers of enamel and dentin materials. Conclusion: The study demonstrated that the use of two materials is well-suited for the restoration of front teeth with their relatively high proportion of enamel. This study will continue further with the compilation of a data pool of optical parameters which will enable the application of calculation models to optimize the optical approximation of the natural tooth. © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.


PubMed | Laser und Medizin Technology
Type: Evaluation Studies | Journal: Dental materials : official publication of the Academy of Dental Materials | Year: 2012

Esthetic restorations require that dental restorative materials have similar optical properties to teeth. To improve the color perception, the inhomogeneous morphology of the native tooth can be imitated by layering two optically different restorative materials. However until now the benefit of this method has not been satisfactorily demonstrated.The optical parameters, absorption coefficient (a), scattering coefficient (s), anisotropy factor g and effective scattering coefficient (s), were determined for the enamel and dentin material of the restorative material systems Artemis() and Herculite XRV(). This was carried out for each material system in the wavelength range between 400 and 700nm using integrating sphere measurements followed by inverse Monte Carlo simulations.Using the optical parameters and a forward Monte Carlo simulation, the color perception of layered samples could be predicted with a sufficient degree of accuracy. The total color impression was shown to be dependent on the sample thickness and the transparency/translucency of the single layers of enamel and dentin materials.The study demonstrated that the use of two materials is well-suited for the restoration of front teeth with their relatively high proportion of enamel. This study will continue further with the compilation of a data pool of optical parameters which will enable the application of calculation models to optimize the optical approximation of the natural tooth.

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