Method, system and computer readable medium for iterative image warping

Abstract

A method of computerized analysis of temporally sequential digital images, including (a) determining first shift values between pixels of a first digital image and corresponding pixels of a second digital image; (b) warping the second digital image based on the first shift values to obtain a first warped image in which spatial locations of pixels are varied in relation to the first shift values; (c) determining second shift values between pixels of the first digital image and pixels of the first warped image; and (d) warping the first warped image based on the second shift values to obtain a second warped image in which spatial locations of pixels of the first warped image are varied in relation to the second shift values. Additional iterations of image warping are possible to enhance image registration between the first digital image and the warped version of the second digital image, followed by image subtraction of the first digital image and the final warped image to produce a difference image from which diagnosis of temporal changes ensues. Temporal subtraction assists radiologists in the detection of interval changes on chest radiographs, and particularly to overcome severe misregistration errors in the temporally sequential images mainly due to differences in a subject's inclination and/or rotation. In the production of shift values used in image warping, initial shift values are obtained by cross-correlation techniques using a template and search regions of interest. Shift vectors and a histogram of shift vectors in each lung are obtained from initial shift values. The histograms of shift vectors are used in the selection of sets of shift values for smoothing, using two-dimensional fitting and subsequent use of fitted shift values in image warping.