Converting a digital radiograph to an absolute thickness map
First Claim
1. A method for calibrating digital data representing a digital image of an object, said method comprising the steps of:
- a. providing a radiation source for directing radiation through a region of said object;
b. providing a radiation detector having a plurality of sensing elements for detecting said radiation;
c. acquiring a flat field image to equalize a response from each said sensing element;
d. recording numerical data indicative of an intensity of said radiation incident on each said sensing element;
e. correlating said numerical data to a measurable property of said object;
f. calibrating said numerical data, comprising the steps of;
i. correcting for variations in a source-detector-distance (SDD) between said source and said detector;
ii. correcting for variations in a source-object-distance (SOD) between said source and said object;
iii. correcting for variations in a spatial frequency response (MTF) of said detector; and
iv. correcting for variations in a geometric profile defining said object; and
g. utilizing said calibrated data to generate a map representing said measurable property.
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Abstract
A digital radiography imaging system for acquiring digital images of an object, and a method for transforming digital images into an absolute thickness map characterizing the object under inspection. The system includes a radiation source for directing radiation through a desired region of the object, and a radiation detector having a plurality of sensing elements for detecting radiation passing through the object. Numerical data generated from each sensing element is calibrated, for example by correcting for variations in radiation paths between the source and detector, by correcting for variations in the spatial frequency response (MTF) of the detector, by correcting for variations in the geometric profile of the object under inspection, and by correcting for material contained in and/or around the object. The calibrated data is processed in order to generate and display an absolute thickness map of the object. The calibration procedures are adapted for extracting a thickness map from both isotope sources and X-ray tube sources.
48 Citations
24 Claims
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1. A method for calibrating digital data representing a digital image of an object, said method comprising the steps of:
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a. providing a radiation source for directing radiation through a region of said object;
b. providing a radiation detector having a plurality of sensing elements for detecting said radiation;
c. acquiring a flat field image to equalize a response from each said sensing element;
d. recording numerical data indicative of an intensity of said radiation incident on each said sensing element;
e. correlating said numerical data to a measurable property of said object;
f. calibrating said numerical data, comprising the steps of;
i. correcting for variations in a source-detector-distance (SDD) between said source and said detector;
ii. correcting for variations in a source-object-distance (SOD) between said source and said object;
iii. correcting for variations in a spatial frequency response (MTF) of said detector; and
iv. correcting for variations in a geometric profile defining said object; and
g. utilizing said calibrated data to generate a map representing said measurable property. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for calibrating digital images, comprising:
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a. a radiation source for directing radiation through a region of an object;
b. a radiation detector having a plurality of sensing elements for detecting said radiation;
c. means for acquiring a flat field image to equalize a response from each said sensing element;
d. means for recording numerical data indicative of an intensity of said radiation incident on each said sensing element;
e. means for correlating said numerical data to a measurable property of said object;
f. means for calibrating said numerical data, comprising;
i. means for correcting for variations in a source-detector-distance (SDD) between said source and said detector;
ii. means for correcting for variations in a source-object-distance (SOD) between said source and said object;
iii. means for correcting for variations in a spatial frequency response (MTF) of said detector;
iv. means for correcting for variations in a geometric profile defining said object; and
g. means for generating a map representing said measurable property from said calibrated data. - View Dependent Claims (10, 11, 12, 13)
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14. A method for calibrating digital data, comprising the steps of:
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a. providing a calibration block having a plurality of thickness regions disposed along a length of said block;
b. acquiring a digital image representing each said thickness region;
c. detecting the boundaries of each said thickness region;
d. sampling an inner area of said image at each said thickness region so as to generate a mean pixel value and an uncertainty representing each said thickness region;
e. mapping each said mean pixel value to a thickness dimension defining each said thickness region; and
f. generating a look-up table to store results from said mapping step (e). - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification