Monte Carlo simulations in complex geometries: Modeling laser light transport in real anatomy of rheumatoid arthritis

The potential of Monte Carlo simulations is demonstrated for the prediction of scattering light distributions in the near infrared spectral range on a model for complex human anatomy, the finger joint. The transition from the Boltzmann transport equation to the Monte Carlo algorithm is described. The origins of optical properties of tissues (absorption coefficient μ a , scattering coefficient μ s , anisotropy factor g) are discussed and illustrated by laboratory measurements. When measuring these parameters, changes were discovered that correlate with the rheumatoid arthritis of a small joint. A realistic model of the rather complex geometry is described. The results of first simulations show a clear distinction between the stray light distribution of healthy and rheumatoid joints and are in good agreement with recent transillumination experiments.