Image reconstruction for a CT system implementing a dual fan beam helical scan
AssigneeGeneral Electric Company
InventorHu Hui
Life of this patent
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Abstract
The present invention, in one form, is an apparatus for performing image reconstruction using data obtained by a dual beam helical scan. In reconstructing an image in accordance with the present invention, projection data from each fan beam measurement is weighted by weighting factors to obtain a reconstructed slice. The data arrays selected and weighting factors applied vary depending on the table speed and the detector spacing measured at the axis of gantry rotation, i.e., the detector z spacing.
Claims18
A system for producing a tomographic image of an object from projection data acquired in a helical scan, said system generating data from a pair of x-ray fan beams disposed along a z axis, said system comprising a data acquisition system configured to:
- (a) create projection data arrays corresponding to the data obtained from each of the x-ray fan beams;
- (b) apply a weighting function to each of the projection data arrays generated in step (a) to generate respective weighted projection data arrays, the weighting function applied being:
- (i) if the table feeding speed s and detector z spacing, d, satisfy the relation d<s<(2.pi./(.pi.+2.gamma..sub.m))d, the helical weighting factors to be applied for each data set, denoted as W1 (.beta.,.gamma.) and W2 (.beta., .gamma.), are:
- ##EQU6## (ii) if the table feeding speed s and detector z spacing, d, satisfy the relation s>((2.pi./(.pi.-2.gamma..sub.m))d, the helical weighting factors to be applied for each data set, denoted as W1 (.beta., .gamma.) and W2 (.beta., .gamma.), are:
- ##EQU7## (c) from the projection data arrays generated in step (b), generate image data arrays to be used to construct a slice image.
A method for producing a tomographic image of an object from projection data acquired in a helical scan, the system generating data from a pair of x-ray fan beams disposed along a z axis, the table feeding speed s and detector z spacing, d, satisfying the relation d<s<(2.pi./(.pi.+2.gamma..sub.m))d, said method comprising the steps of:
- (a) creating projection data arrays corresponding to the data obtained from each of the x-ray fan beams;
- (b) applying a weighting function to each of the projection data arrays generated in step (a) to generate respective weighted projection data arrays, the weighting factors to be applied for each data set, denoted as W1 (.beta., .gamma.) and W2 (.beta., .gamma.), being:
- ##EQU8## (c) from the projection data arrays generated in step (b), generating image data arrays to be used to construct a slice image.
A method for producing a tomographic image of an object from projection data acquired in a helical scan, the system generating data from a pair of x-ray fan beams disposed along a z axis, the table feeding speed s and detector z spacing, d, satisfying the relation s>((2.pi./ (.pi.-2.gamma..sub.m))d, said method comprising the steps of:
- (a) creating projection data arrays corresponding to the data obtained from each of the x-ray fan beams;
- (b) applying a weighting function to each of the projection data arrays generated in step (a) to generate respective weighted projection data arrays, the weighting factors to be applied for each data set, denoted as W1 (.beta., .gamma.) and W2 (.beta., .gamma.), being:
- ##EQU9## (c) from the projection data arrays generated in step (b), generating image data arrays to be used to construct a slice image.
Dependencies are inferred from the claim text.