EP0426464A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Computerized tomographic image reconstruction method for helical scanning
Assignee: General Electric Co
•
Filing: 1990-11-01
•
Granted: —
•
Expires: 2010-11-01
Abstract
Abstract A method of reducing image artifacts in images acquired with fan beam, helical scanning, tomographic imaging systems uses half scans of less than 360° of projection data of an imaged object on each side of the slice plane being imaged. The half scans are weighted with half scan weighting factors to compensate for redundant data and are weighted with helical scanning weighting factors to interpolate the half scans projection data to projection data at the slice plane. The imaged object may be moved one slice thickness for each 360° of scanning so that the half scans are concentrated closer to the slice plane thereby reducing interpolation errors. Alternatively, for a series of slice images, the imaged object may be moved one slice thickness for each half scan to reduce average slice acquisition time.
Inventors
- 👤 Kevin Franklin King
- 👤 Carl Ross Crawford
- 👤 Albert Henry Roger Lonn
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-23 16:01
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/02; A61B6/03; A61B6/032; A61B6/027; G; G06; G06T; G06T12/00; G06T12/10
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
150 words
A method of producing a tomographic image of an imaged object from data acquired in a helical scan, the data comprising a series of fan beam projections at a plurality of gantry angles ϑ about a z axis, the fan beam projections subtending an angle 2φ max , comprising the steps of: a) identifying a slice plane Z sp relative to the imaged object and parallel to the slice plane; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane at a gantry angle of ϑ₀; c) acquiring a first half scan data set prior to the imaging plane crossing the slice plane; d) acquiring a second half scan data set subsequent to the imaging plane crossing the slice plane; and e) interpolating and reconstructing a tomographic image at the slice plane from the first and second half scans.
Claim 2
Independent Claim
150 words
A method of producing a tomographic image of an imaged object from data acquired in a helical scan, the data comprising a series of fan beam projections at a plurality of gantry angles ϑ about a z axis, the fan beam projections subtending an angle 2φ max , comprising the steps of: a) identifying a slice plane Z sp relative to the imaged object and parallel to the slice plane; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane at a gantry angle of ϑ₀; c) acquiring a first half scan data set prior to the imaging plane crossing the slice plane; d) acquiring a second half scan data set subsequent to the imaging plane crossing the slice plane; and e) interpolating and reconstructing a tomographic image at the slice plane from the first and second half scans.
Claim 3
Dependent Claim
37 words
The method of claim 1 wherein the first half scan data set is acquired for ϑ such that ϑ₀-π-2φ max <ϑ<ϑ₀ and the second half scan data set is acquired for ϑ such that ϑ₀<ϑ<ϑ₀+π+2φ max .
Claim 4
Dependent Claim
46 words
The method of claim 1 wherein the first half scan data set is acquired for ϑ such that ϑ₀-α<ϑ<ϑ₀ and the second half scan data set is acquired for ϑ such that ϑ₀<ϑ<ϑ₀+α where α is less than 2π but not less than π+2φ max .
Claim 5
Dependent Claim
70 words
The method of claim 1 where the tomographic image is interpolated and reconstructed from the first and second half scan data sets by: applying a half scan weighting function to the data in the first and second half scan data sets; applying a helical scan weighting function to the data in the first and second half scan data sets; and reconstructing the first and second weighted half scan data sets.
Claim 6
Dependent Claim
33 words
The method of claim 4 including the step of summing the data of the weighted first and second half scan data sets before reconstructing the first and second weighted half scan data sets.
Claim 7
Dependent Claim
26 words
The method of claim 4 including the step of combining the weighted first and second half scan data sets into a larger data set before reconstruction.
Claim 8
Dependent Claim
53 words
The method of claim 4 where the half scan weighting function is such that the sum of the weights assigned to redundant data within a half scan is equal to the weight assigned to non-redundant data within the half scan and corresponding data between half scans are assigned the same half scan weights.
Claim 9
Dependent Claim
17 words
The method of claim 4 where the half scan weighting function is one of two binary values.
Claim 10
Dependent Claim
11 words
The method of claim 8 wherein one binary value is zero.
Claim 11
Dependent Claim
56 words
The method of claim 3 where the half scan weighting function is constant within zones of non-redundant data and varies with angles ϑ according to a function f(x)=3x²-2x³ in zones of redundant data where x is a variable that varies linearly as a function of angles ϑ between zero and 1 in zones of redundant data.
Claim 12
Independent Claim
159 words
A method of producing a series of tomographic images of an imaged object, separated by slice thickness D, from data acquired in a helical scan, the data comprising a series of fan beam projections within an imaging plane at a plurality of gantry angles ϑ about a z axis, comprising the steps of: a) identifying a slice plane relative to the imaged object; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane; c) acquiring a first half scan of projection data prior to the imaging plane crossing the slice plane; d) acquiring a second half scan of projection data subsequent to the imaging plane crossing the slice plane; e) moving the imaged object so that the imaged object is moved D along the z-axis during each half scan; and f) interpolating and reconstructing a tomographic image at the slice plane from the first and second half scans.
Claim 13
Independent Claim
159 words
A method of producing a series of tomographic images of an imaged object, separated by slice thickness D, from data acquired in a helical scan, the data comprising a series of fan beam projections within an imaging plane at a plurality of gantry angles ϑ about a z axis, comprising the steps of: a) identifying a slice plane relative to the imaged object; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane; c) acquiring a first half scan of projection data prior to the imaging plane crossing the slice plane; d) acquiring a second half scan of projection data subsequent to the imaging plane crossing the slice plane; e) moving the imaged object so that the imaged object is moved D along the z-axis during each half scan; and f) interpolating and reconstructing a tomographic image at the slice plane from the first and second half scans.
Claim 14
Independent Claim
157 words
A method of producing a series of tomographic images of an imaged object, separated by slice thickness D, from data acquired in a helical scan, the data comprising a series of fan beam projections within an imaging plane at a plurality of gantry angles ϑ about a z axis, comprising the steps of: a) identifying a slice plane relative to the imaged object; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane and so that the imaged object is moved D along the z-axis during each 2π of gantry rotation; c) acquiring a first half scan of projection data prior to the imaging plane crossing the slice plane; d) acquiring a second half scan of projection data subsequent to the imaging plane crossing the slice plane; and e) interpolating and reconstructing a tomographic image at the slice plane from the first and second half scans.
Claim 15
Independent Claim
157 words
A method of producing a series of tomographic images of an imaged object, separated by slice thickness D, from data acquired in a helical scan, the data comprising a series of fan beam projections within an imaging plane at a plurality of gantry angles ϑ about a z axis, comprising the steps of: a) identifying a slice plane relative to the imaged object; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane and so that the imaged object is moved D along the z-axis during each 2π of gantry rotation; c) acquiring a first half scan of projection data prior to the imaging plane crossing the slice plane; d) acquiring a second half scan of projection data subsequent to the imaging plane crossing the slice plane; and e) interpolating and reconstructing a tomographic image at the slice plane from the first and second half scans.
Claim 16
Dependent Claim
178 words
Apparatus for producing a series of tomographic images of an imaged object, separated by slice thickness D, from data acquired in a helical scan, the data comprising series of fan beam projections within an imaging plane at a plurality of gantry angles 0 about a z axis, the apparatus comprising: a gantry (16) and means (56) for moving the gantry, means (10) supported by the gantry for producing a fan beam (24), means (22, 52) for moving the imaged object along an z-axis, and processing means arranged to a) identify a slice plane relative to the imaged object; b) cause the imaged object to move along the z-axis and cause the gantry to rotate so that the imaging plane crosses the slice plane, c) acquire a first half scan of projection data prior to the imaging plane crossing the slice plane; d) acquire a second half scan of projection data subsequent to the imaging plane crossing the slice plane; and e) interpolate and reconstruct a tomographic image at the slice plane from the first and second half scans.
Claim 17
Dependent Claim
178 words
Apparatus for producing a series of tomographic images of an imaged object, separated by slice thickness D, from data acquired in a helical scan, the data comprising series of fan beam projections within an imaging plane at a plurality of gantry angles 0 about a z axis, the apparatus comprising: a gantry (16) and means (56) for moving the gantry, means (10) supported by the gantry for producing a fan beam (24), means (22, 52) for moving the imaged object along an z-axis, and processing means arranged to a) identify a slice plane relative to the imaged object; b) cause the imaged object to move along the z-axis and cause the gantry to rotate so that the imaging plane crosses the slice plane, c) acquire a first half scan of projection data prior to the imaging plane crossing the slice plane; d) acquire a second half scan of projection data subsequent to the imaging plane crossing the slice plane; and e) interpolate and reconstruct a tomographic image at the slice plane from the first and second half scans.
Claim 18
Dependent Claim
14 words
Apparatus arranged to carry out the method of anyone of claims 1 to 12.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.