Photodiagnosis and fluorescence imaging in clinical practice.

For cancer diagnosis clinicians rely upon histo pathological preparations in their broadest sense and the characteristic microscopic features which represent malignant changes. Standard method of in-vivo sampling (biopsy) uses white light indicating abnormal tissue. The manner in which light interacts with a specific tissue type is dictated by the wavelength dependent scattering and absorbtion properties. In the UV and visible part of the spectrum the tissue optical properties are dominated by the endogenous chromophores which is different for normal/abnormal tissue. It follows that abnormal tissue, absorbs light and fluoresces differently to normal tissue at specific light wavelengths. Autofluorescence takes advantage of this principle. Enhanced fluorescence employs exogenous markers to produce better definition. Fluorescence imaging has become an important diagnostic tool to highlight cancer at an early stage of development and/or to guide biopsy from representative samples.