Time-resolved photon migration in a heterogeneous tissue-vessel model

We investigate the relationship between the apparent absorption coefficient and actual absorption coefficient inside the vessels. This analytical formula predicts that the apparent absorption coefficient measured on a biological organ is a volume-weighted sum of the absorption coefficients of different absorbing components. Further, we present some apparent absorption coefficients measured in vivo in animals and humans and show that ignoring the background absorption can lead to significant errors in oxygenation determination.