Patent ID: 6333991
Filing Date: 2001-12-25
Classification: A61N,G06T

Abstract:
A method of analysing a radiographic image comprising the following steps;(a) preparing a reference image, wherein the reference image is one of a portal image from a first treatment, a pre-treatment test image, or a digitally reconstructed radiograph;(b) preparing a sample image;(c) preparing a reference radiation field image and a sample radiation field image from the reference image and the sample image respectively by, in order, (i) defining a threshold value and (ii) setting pixels within the respective images to a dark or a bright state if darker or brighter than the threshold value;(d) optionally, comparing the reference radiation field image and the sample radiation field image to determine at least one of their relative rotation, translation and scaling;(e) subtracting one of the radiation field images from the other thereby to obtain a difference image;(f) inspecting the difference image to ascertain changes in the radiation field between preparation of the reference image and the sample image.