Computed tomography system with correction for z-axis detector non-uniformity
AssigneeGeneral Electric Company
InventorsJiang Hsieh, Dale R. Thayer
Life of this patent
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Abstract
An x-ray CT scanner acquires projection profiles P during a scan which are corrected for errors caused by non-uniform response of the detectors along the z-axis. In addition to corrections using a calibration vector Q that offsets errors caused by variations in the detector response, additional corrections are made to offset object dependent errors caused by the same variations in detector response when imaging certain objects.
Claims8
A method for correcting x-ray data for a computed tomography system having an x-ray source for producing a fan beam of x-rays along a fan beam plane and with a thickness along an axis normal to the fan beam plane, and having a set of detector elements disposed in the fan beam of x-rays to produce a corresponding set of attenuation signals that indicate the x-ray flux density profile of the fan beam, the steps comprising:
- a) acquiring a set of attenuation signals from the detector elements during a calibration scan and calculating a calibration vector Q which indicates corrections to be made to the attenuation signals as a function of the location of the fan beam plane along said axis;
- b) acquiring a set of attenuation signals from the detector elements during a scan of a subject and producing a projection profile P;
- c) correcting the projection profile P using the calibration vector Q and the measured position of the fan beam plane along said axis;
- d) calculating an error vector E from the projection profile P indicative of the errors therein caused by non-uniform response of detector elements along said axis;
- e) calculating an offset value .DELTA.Z from the error vector E and the calibration vector Q;
- f) further correcting the projection profile P by calculating corrections C based on the offset value .DELTA.Z, the calibration vector Q and projection profile P;
- g) repeating steps b) through f) to perform a scan in which a plurality of corrected projection profiles are produced;
- and
- h) reconstructing an image using said plurality of corrected projection profiles.
Dependencies are inferred from the claim text.