Method, system and computer readable medium for iterative image warping prior to temporal subtraction of chest radiographs in the detection of interval changes
First Claim
1. In a method for computerized analysis of temporally sequential digital chest images, each including data corresponding to a pair of lungs, the improvement comprising the steps of:
- (a) determining first shift values between pixels of a first digital chest image and corresponding pixels of a second digital chest image, comprising,selecting plural template regions of interest (ROIs) in the first digital chest image and corresponding search area ROIs in the second digital chest image,determining shift values between pixels centered in each template ROI and pixels centered in a respective search area ROI and exhibiting highest cross-correlation with respect to said template ROI,determining shift vectors for each of said shift values, a first cumulative histogram of said shift vectors for pixels in one lung, and a second cumulative histogram of said shift vectors for pixels in the other lung,selecting, based on characteristics of said first and second cumulative histograms of shift vectors, plural of said shift values for derivation of fitted shift values, perfoming two-dimentional fitting on the shift values selected in the preceding step to derive said fitted shift values which serve as said first shift values; and
(b) warping said second digital chest image using the first shift values to obtain a warped image in which spatial locations of pixels are varied in relation to said first shift values.
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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.
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Citations
60 Claims
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1. In a method for computerized analysis of temporally sequential digital chest images, each including data corresponding to a pair of lungs, the improvement comprising the steps of:
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(a) determining first shift values between pixels of a first digital chest image and corresponding pixels of a second digital chest image, comprising, selecting plural template regions of interest (ROIs) in the first digital chest image and corresponding search area ROIs in the second digital chest image, determining shift values between pixels centered in each template ROI and pixels centered in a respective search area ROI and exhibiting highest cross-correlation with respect to said template ROI, determining shift vectors for each of said shift values, a first cumulative histogram of said shift vectors for pixels in one lung, and a second cumulative histogram of said shift vectors for pixels in the other lung, selecting, based on characteristics of said first and second cumulative histograms of shift vectors, plural of said shift values for derivation of fitted shift values, perfoming two-dimentional fitting on the shift values selected in the preceding step to derive said fitted shift values which serve as said first shift values; and (b) warping said second digital chest image using the first shift values to obtain a warped image in which spatial locations of pixels are varied in relation to said first shift values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A computer readable medium storing computer instructions for computerized analysis of temporally sequential digital chest images, each including data corresponding to a pair of lungs, by performing the steps of:
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(a) determining first shift values between pixels of a first digital chest image and corresponding pixels of a second digital chest image, comprising, selecting plural template regions of interest (ROIs) in the first digital chest image and corresponding search area ROIs in the second digital chest image, determining shift values between pixels centered in each template ROI and pixels centered in a respective search area ROI and exhibiting highest cross-correlation with respect to said template ROI, determining shift vectors for each of said shift values, a first cumulative histogram of said shift vectors for pixels in one lung, and a second cumulative histogram of said shift vectors for pixels in the other lung, selecting, based on characteristics of said first and second cumulative histograms of shift vectors, plural of said shift values for derivation of fitted shift, and performing two-dimensional fitting on the shift values selected in the preceding step to derive said first shift values; and (b) warping said second digital chest image using the first shift values to obtain a warped image in which spatial locations of pixels are varied in relation to said first shift values. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A system for computerized analysis of temporally sequential digital chest images, each including data corresponding to a pair of lungs, the improvement comprising:
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(a) means for determining first shift values between pixels of a first digital image and corresponding pixels of a second digital image, comprising, means for selecting plural template regions of interest (ROIs) in the first digital image and corresponding search area ROIs in the second image, means for determining shift values between pixels centered in each template ROI and pixels centered in a respective search area ROI and exhibiting highest cross-correlation with respect to said template ROI, means for determining shift vectors for each of said shift values, a first cumulative histogram of said shift vectors for pixels in one lung, and a second cumulative histogram of said shift vectors for pixels in the other lung, means for selecting, based on characteristics of said first and second cumulative histograms of shift vectors, plural of said shift values for derivation of fitted shift values to serve as said first shift values, and means for performing two-dimensional fitting on the shift values selected in the preceding step to derive said first shift values; and (b) means for warping said second digital image based on the first shift values to obtain a warped image in which spatial locations of pixels are varied in relation to said first shift values. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60)
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Specification