Converting a digital radiograph to an absolute thickness map
First Claim
1. A method for generating a wall thickness map of an object by converting digital data representing a digital radiographic image into a display map representing the absolute thickness of the object, said method comprising the steps of:
- a. providing an X-ray or gamma ray 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 measurement of the thickness 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 by correcting the flux of X-rays or gamma rays to account for scattering;
ii. correcting for variations in a source-object-distance (SOD) between said source and said object by correcting the flux of X-rays or gamma rays to account for scattering;
iii. correcting for variations in a spatial frequency response (MTF) of said detector to determine the spatial extent and penetration depth of features within the object; and
iv. correcting for variations in a geometric profile defining said object; and
g. generating an absolute thickness map for a region of said object from said calibrated data.
3 Assignments
0 Petitions
Accused Products
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.
77 Citations
23 Claims
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1. A method for generating a wall thickness map of an object by converting digital data representing a digital radiographic image into a display map representing the absolute thickness of the object, said method comprising the steps of:
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a. providing an X-ray or gamma ray 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 measurement of the thickness 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 by correcting the flux of X-rays or gamma rays to account for scattering; ii. correcting for variations in a source-object-distance (SOD) between said source and said object by correcting the flux of X-rays or gamma rays to account for scattering; iii. correcting for variations in a spatial frequency response (MTF) of said detector to determine the spatial extent and penetration depth of features within the object; and iv. correcting for variations in a geometric profile defining said object; and g. generating an absolute thickness map for a region of said object from said calibrated data. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for generating a wall thickness map of an object by converting digital data representing digital radiographic images into a display map representing the absolute thickness of a region of the object, the system comprising:
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a. a radiation source for directing X-ray or gamma ray 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 measurement of the thickness 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 an absolute thickness of the region of the object from said calibrated data. - View Dependent Claims (9, 10, 11, 12)
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13. A method for calibrating digital data and using the data to generate a thickness map of an object, comprising the steps of:
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providing an X-ray gamma ray radiation source and radiation detector; providing a calibration block having a plurality of thickness regions disposed along a length of said block; acquiring a digital image with said radiation detector representing each of said thickness regions; detecting the boundaries of each said thickness region; 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; mapping each said mean pixel value to a thickness dimension defining each said thickness region; generating a look-up table to store results from said mapping step; and generating a thickness map using the look up table. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification