Measurement depth of laser-induced tissue fluorescence with application to laser angioplasty

Laser-induced fluorescence spectroscopy can be used to discriminate between normal and atherosclerotic tissue and guide the delivery of high-power laser energy for laser angioplasty. The depth of tissue from which fluorescence is measured should closely match the depth of laser ablation and, from a practical standpoint, should be neither too small nor too large. This paper investigates the depth of the fluorescence signal. A simple mathematical model is presented. An experimental procedure for determining this depth is described. The results agree well with the model. The implications of the findings to the development of a practical fluorescence-guided laser angioplasty system are discussed.