Patent ID: 6128525
Filing Date: 2000-10-03
Classification: A61B,A61N

Abstract:
A method for controlling the dosimetry of photodynamic therapy (PDT) that involves exposing a site to be treated to treatment light in order to generate toxic products at the site and other photoproducts, comprising the steps of:selecting at least one photoproduct such that the photoproduct has an identifying characteristic comprising a peak in a fluorescence spectrum of the at least one photoproduct and such that the level of the photoproduct being generated is proportional to the toxic effect of the PDT therapy;monitoring the at least one photoproduct using the identifying characteristic to determine the level of the photoproduct being generated, the monitoring performed by a) exposing the treatment site to an excitation light; b) capturing resulting fluorescence images by i) capturing a first fluorescence image over a narrow wavelength band around the peak in the fluorescence spectrum of the photoproduct; ii) capturing a second fluorescence image over a wavelength band adjacent to the photoproduct peak and remote from any other PDT fluorescence peaks; and, iii) dividing the fluorescence image captured in step i) by the fluorescence image captured in step b) to obtain a ratio image; c) analysing the captured fluorescence images to determine the level of the at least one photoproduct by i) obtaining the ratio image of the site before exposing the site to treatment light; and, ii) dividing each ratio image acquired during PDT treatment by the ratio image of step a) to determine the distribution at the site of the levels of the at least one photoproduct; d) repeating steps a), b), and c) at set intervals;terminating the photodynamic therapy when the at least one photoproduct being monitored reaches a predetermined level; and,modifying the distribution of the treatment light at the site based on the distribution at the site of the levels of the at least one photoproduct by controlling a light valve in the path of the treatment light to regulate how much treatment light will be received by different areas of the treatment site, wherein the light valve is a digital micromirror device.