EP0430549A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Helical scan computed tomography
Assignee: General Electric Co
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Filing: 1990-11-21
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Granted: —
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Expires: 2010-11-21
Abstract
Abstract A method of and apparatus for reducing image artifacts in images acquired with fan beam, helical scanning, tomographic imaging systems rebins the fan beam data into parallel beam projection sets. Data is spliced from first areas of the parallel beam projection data to second areas to create a set of 2π radians of complete projection data. The 2π of projection data is divided into half scans which are interpolated and extrapolated to produce a new projection set at the slice plane with reduced helical offset error. A feathering function is used to blend the discontinuities in the interpolation and extrapolation weights to prevent streak image artifacts.
Inventors
- 👤 Carl Ross Crawford
- 👤 Kevin Franklin King
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 20:51
CPC Classifications
G; G06; G06T; G06T12/00; G06T12/10; A; A61; A61B; A61B6/00; A61B6/02; A61B6/027
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
193 words
A method of producing a tomographic image of an imaged object from data acquired in a helical scan, the data acquired as a series of fan beam projections at a plurality of gantry angles ϑ about a z axis and within an image plane, the source-vertex projections including a plurality of data at fan beam angles φ, comprising the steps of: a) identifying a slice plane z sp relative to the imaged object and parallel to the image plane; b) acquiring a fan beam projection set of data over 2π of source rotation; c) moving the imaged object along the z-axis and rotating the source so that the imaging plane crosses the slice plane during the acquisition of a fan beam projection set; d) rebinning the fan beam projection set into a parallel projection set; e) dividing the parallel beam projection set into two half scans; f) splicing data between the half scans to create 2π of complete parallel beam projections; g) extrapolating and interpolating the data of the half scans to a slice plane parallel beam projection set; and h) reconstructing the slice plane parallel beam projection set into a slice image.
Claim 2
Independent Claim
193 words
A method of producing a tomographic image of an imaged object from data acquired in a helical scan, the data acquired as a series of fan beam projections at a plurality of gantry angles ϑ about a z axis and within an image plane, the source-vertex projections including a plurality of data at fan beam angles φ, comprising the steps of: a) identifying a slice plane z sp relative to the imaged object and parallel to the image plane; b) acquiring a fan beam projection set of data over 2π of source rotation; c) moving the imaged object along the z-axis and rotating the source so that the imaging plane crosses the slice plane during the acquisition of a fan beam projection set; d) rebinning the fan beam projection set into a parallel projection set; e) dividing the parallel beam projection set into two half scans; f) splicing data between the half scans to create 2π of complete parallel beam projections; g) extrapolating and interpolating the data of the half scans to a slice plane parallel beam projection set; and h) reconstructing the slice plane parallel beam projection set into a slice image.
Claim 3
Dependent Claim
39 words
The method of claim 1 where the data of the half scans is extrapolated and interpolated by applying a weighting function to the half scans and reconstructing the combined weighted half scans into a slice image per step (h).
Claim 4
Dependent Claim
34 words
The method of claim 2 wherein the weighting function for pairs of redundant data within each half scan add to a constant and the weight for any such datum is a function of ϑ.
Claim 5
Dependent Claim
17 words
The method of claim 1 including the step of applying a feathering weighting to the half scans.
Claim 6
Dependent Claim
23 words
The method of claim 1 where the slice plane crosses the imaging plane midway through the acquisition of the fan beam projection set.
Claim 7
Dependent Claim
11 words
Apparatus arranged to carry out the method of any preceding claim.
Claim 8
Dependent Claim
225 words
Apparatus for producing a tomographic image of an imaged object from data acquired in a helical scan, comprising a gantry, a source supported by the gantry for producing a fan beam, means for moving the gantry, means for moving the imaged object, means for acquiring data as a series of fan beam projections at a plurality of gantry angles ϑ about a z-axis and within an image plane, the source-vertex projections including a plurality of data at fan beam angles ϑ, and processing means for: a) identifying a slice plane z sp relative to the imaged object and parallel to the image plane; b) causing the acquisition of a fan beam projection set of data over 2π of source rotation; c) causing the imaged object to be moved along the z-axis and the source to be rotated so that the imaging plane crosses the slice plane during the acquisition of a fan beam projection set; d) rebinning the fan beam projection set into a parallel projection set; e) dividing the parallel beam projection set into two half scans; f) splicing data between the half scans to create 2π of complete parallel beam projections; g) extrapolating and interpolating the data of the half scans to a slice plane parallel beam projection set; and h) reconstructing the slice plane parallel beam projection set into a slice image.
Claim 9
Dependent Claim
225 words
Apparatus for producing a tomographic image of an imaged object from data acquired in a helical scan, comprising a gantry, a source supported by the gantry for producing a fan beam, means for moving the gantry, means for moving the imaged object, means for acquiring data as a series of fan beam projections at a plurality of gantry angles ϑ about a z-axis and within an image plane, the source-vertex projections including a plurality of data at fan beam angles ϑ, and processing means for: a) identifying a slice plane z sp relative to the imaged object and parallel to the image plane; b) causing the acquisition of a fan beam projection set of data over 2π of source rotation; c) causing the imaged object to be moved along the z-axis and the source to be rotated so that the imaging plane crosses the slice plane during the acquisition of a fan beam projection set; d) rebinning the fan beam projection set into a parallel projection set; e) dividing the parallel beam projection set into two half scans; f) splicing data between the half scans to create 2π of complete parallel beam projections; g) extrapolating and interpolating the data of the half scans to a slice plane parallel beam projection set; and h) reconstructing the slice plane parallel beam projection set into a slice image.
References Cited (Backward Citations)
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