In Vivo Optical Measurements for Diagnostics and Monitoring of Treatment

The interaction of light with tissue and its use for medical purposes has been under investigation for centuries. Since the early nineteen sixties, the development of novel optical technology and advances in laser design/technology allowed a wide range of innovative applications in many fields of medicine. For the majority of light applications in medicine the distribution of light within tissue is of fundamental importance. The light distribution is determined by the optical properties of the tissue; scattering and absorption. This thesis focuses on two applications of light in medicine, photodynamic therapy (PDT) and optical diagnostics. For each application the effect of differences in and changes of tissue optical properties are investigated. The distribution of light within tissue is of vital importance in PDT and is strongly dependent on the in vivo optical properties. In vivo differences and variations in optical properties are also critically important for optical diagnostics. The hypothesis presented is that the underlying cause of the current limitations in clinical PDT and low sensitivity in optical diagnosis are due to the heterogeneous and dynamic nature of tissue optical properties. This thesis tests this hypothesis by investigating the spatial distribution, inter patient differences, and temporal behaviour of in vivo optical properties by means of in vivo light measurement.

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