Abstract
Light can be used to probe the function and structure of human tissues. We have been exploring two distinct methods: (i) externally emitting light into tissue and measuring the transmitted light to characterize a region through which the light has passed, and (ii) internally generating light within tissue and using the radiated light as a quantitative homing beacon. The emitted-light approach falls within the domain of spectroscopy, and has allowed for imaging of intracranial haemorrhage in newborns and of brain functions in adults. The generated-light approach is conceptually parallel to positron emission tomography (PET) or nuclear medicine scanning, and has allowed for real-time, non-invasive monitoring and imaging of infection and gene expression in vivo using low-light cameras and ordinary lenses. In this paper, we discuss recent results and speculate on the applications of such techniques.