EP0430506A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Reducing patient translation artifacts in tomographic imaging
Assignee: General Electric Co
•
Filing: 1990-11-16
•
Granted: —
•
Expires: 2010-11-16
Abstract
Abstract A method of reducing artifacts in images acquired with fan beam, helical scanning, tomographic imaging systems, applies a weighting function to the tomographic projection set. The weighting function reduces the contribution to the final image of projection data with large helical offset. Other redundant data within the projection set is increased in weight by the weighting function to prevent image artifacts from the weighting. In one embodiment, the projection set is centered on the slice plane to avoid discontinuities in the projection data caused by the weighting functions. Apparatus for carrying out the method is disclosed.
Inventors
- 👤 Carl Ross Crawford
- 👤 Kevin Franklin King
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 00:52
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: 14
Claim 1
Independent Claim
138 words
A method of producing a tomographic image of an imaged object from projection data acquired in a helical scan, the data derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z axis and having a helical offset along the z axis, the fan beam projections subtending an angle 2φ max , comprising the steps of: a) acquiring projection data over 360° of gantry rotation; b) reducing the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; c) increasing the relative contribution of a second set of data in the projection set redundant with the first set of data; and d) constructing an image from the first and second data set and the remaining data of the projection set.
Claim 2
Independent Claim
138 words
A method of producing a tomographic image of an imaged object from projection data acquired in a helical scan, the data derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z axis and having a helical offset along the z axis, the fan beam projections subtending an angle 2φ max , comprising the steps of: a) acquiring projection data over 360° of gantry rotation; b) reducing the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; c) increasing the relative contribution of a second set of data in the projection set redundant with the first set of data; and d) constructing an image from the first and second data set and the remaining data of the projection set.
Claim 3
Dependent Claim
31 words
The method of claim 1 where the step of reducing comprises assigning a weighting factor to the projection data wherein said weighting factor decreases monotonically as a function of helical offset.
Claim 4
Dependent Claim
30 words
The method of claim 1 where the step of reducing comprises assigning a weighting factor to the projection data wherein said weighting factor is a cubic function of helical offset.
Claim 5
Dependent Claim
31 words
The method of claim 1 where the step of reducing comprises assigning a weighting factor to the projection data wherein said weighting factor is a piecewise continuous function of helical offset.
Claim 6
Independent Claim
183 words
A method of producing a tomographic image of an imaged object from projection data acquired in a helical scan, the data derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z axis and having a helical offset along the 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 image 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 π and acquiring projection data over 360° of gantry rotation; c) reducing the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; d) increasing the relative contribution of a second set of data in the projection set redundant with the first set of data; and e) constructing an image from the first and second data set and the remaining data of the projection set.
Claim 7
Independent Claim
183 words
A method of producing a tomographic image of an imaged object from projection data acquired in a helical scan, the data derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z axis and having a helical offset along the 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 image 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 π and acquiring projection data over 360° of gantry rotation; c) reducing the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; d) increasing the relative contribution of a second set of data in the projection set redundant with the first set of data; and e) constructing an image from the first and second data set and the remaining data of the projection set.
Claim 8
Dependent Claim
35 words
The method of claim 5 wherein the first set of data comprises two distinct regions, one including the first projections of the projection set and the other including the last projections of the projection set.
Claim 9
Dependent Claim
20 words
The method of claim 6 wherein the data of the two distinct regions are symmetrically disposed about the slice plane.
Claim 10
Dependent Claim
11 words
Apparatus arranged to carry out the method of any preceding claim.
Claim 11
Dependent Claim
173 words
Apparatus for producing a tomographic image of an imaged object from projection data acquired in a helical scan, comprising a gantry, means supported by the gantry for producing a fan beam, means for acquiring projection data, means for moving the imaged object along the z-axis and processing means arranged to cause: the data to be derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z-axis and having a helical offset along the z-axis, the fan beam projections subtending an angle 2φ max , and to cause: a) acquisition of projection data over 360° of gantry rotation: b) reduction of the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; c) increase of the relative contribution of a second set of data in the projection set redundant with the first set of data; and d) construction of an image from the first and second data set and the remaining data of the projection set.
Claim 12
Dependent Claim
173 words
Apparatus for producing a tomographic image of an imaged object from projection data acquired in a helical scan, comprising a gantry, means supported by the gantry for producing a fan beam, means for acquiring projection data, means for moving the imaged object along the z-axis and processing means arranged to cause: the data to be derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z-axis and having a helical offset along the z-axis, the fan beam projections subtending an angle 2φ max , and to cause: a) acquisition of projection data over 360° of gantry rotation: b) reduction of the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; c) increase of the relative contribution of a second set of data in the projection set redundant with the first set of data; and d) construction of an image from the first and second data set and the remaining data of the projection set.
Claim 13
Dependent Claim
221 words
Apparatus for producing a tomographic image of an imaged object from projection data acquired in a helical scan, comprising a gantry, means supported by the gantry for producing a fan beam, means for acquiring projection data, means for moving the imaged object along the z-axis and processing means arranged to cause: the data to be derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z-axis and having a helical offset along the z-axis, the fan beam projections subtending an angle 2φ max , and to cause: a) identification of a slice plane z sp relative to the imaged object and parallel to the image plane; b) movement of the imaged object along the z-axis and rotation of the gantry so that the imaging plane crosses the slice place at a gantry angle of π and acquisition of projection data over 360° of gantry rotation; c) reduction of the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; d) increase of the relative contribution of a second set of data in the projection set redundant with the first set of data; and e) construction of an image from the first and second data set and the remaining data of the projection set.
Claim 14
Dependent Claim
221 words
Apparatus for producing a tomographic image of an imaged object from projection data acquired in a helical scan, comprising a gantry, means supported by the gantry for producing a fan beam, means for acquiring projection data, means for moving the imaged object along the z-axis and processing means arranged to cause: the data to be derived from a series of fan beam projections at a plurality of gantry angles ϑ about a z-axis and having a helical offset along the z-axis, the fan beam projections subtending an angle 2φ max , and to cause: a) identification of a slice plane z sp relative to the imaged object and parallel to the image plane; b) movement of the imaged object along the z-axis and rotation of the gantry so that the imaging plane crosses the slice place at a gantry angle of π and acquisition of projection data over 360° of gantry rotation; c) reduction of the relative contribution of a first set of data in the projection set having helical offset of greater than a predetermined value; d) increase of the relative contribution of a second set of data in the projection set redundant with the first set of data; and e) construction of an image from the first and second data set and the remaining data of the projection set.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.