Patent US5301108A successfully refreshed from Google Patents.
US5301108A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Computed tomography system with z-axis correction
Assignee: General Electric Co
•
Filing: 1993-02-01
•
Granted: 1994-04-05
•
Expires: 2013-02-01
Abstract
Abstract An x-ray CT scanner is operated in a calibration procedure to produce error signature vectors that indicate detector elements that have a non-uniform response along the z-axis and which may generate ring or band artifacts when certain anatomies are scanned. A correction process employs these error signatures during the scan to determine when correction is necessary and to make those corrections to the projection data as it is acquired.
Inventors
- 👤 Jiang Hsieh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 21:17
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/02; A61B6/03; A61B6/032; A61B6/40; A61B6/4021; A61B6/4035; A61B6/58; A61B6/582; A61B6/583; G; G01; G01T; G01T1/00; G01T1/29; G01T1/2914; G01T1/2985; G06; G06T; G06T12/00; G06T12/10
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
249 words
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 in a direction 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: acquiring a set of attenuation signals from the detector elements with a reference phantom disposed in the fan beam of x-rays that attenuates the x-rays such that the flux density of the x-rays striking the detector elements has a substantial gradient along the thickness direction; filtering the acquired set of attenuation signals to produce an error signature vector having elements whose values are indicative of variations in the response of detector elements along the thickness direction; acquiring sets of attenuation signals from the detector elements with a subject to be imaged disposed in the fan beam of x-rays and correcting each set of attenuation signals prior to reconstructing an image by: a) producing an error candidate vector from said set of attenuation signals by filtering therefrom variations in the attenuation signals caused substantially by structures in the subject to be imaged; b) comparing the error signature vector with the error candidate vector to identify specific attenuation signals in the set of attenuation signals that require correction; and c) correcting the identified attenuation signals.
Claim 2
Independent Claim
249 words
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 in a direction 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: acquiring a set of attenuation signals from the detector elements with a reference phantom disposed in the fan beam of x-rays that attenuates the x-rays such that the flux density of the x-rays striking the detector elements has a substantial gradient along the thickness direction; filtering the acquired set of attenuation signals to produce an error signature vector having elements whose values are indicative of variations in the response of detector elements along the thickness direction; acquiring sets of attenuation signals from the detector elements with a subject to be imaged disposed in the fan beam of x-rays and correcting each set of attenuation signals prior to reconstructing an image by: a) producing an error candidate vector from said set of attenuation signals by filtering therefrom variations in the attenuation signals caused substantially by structures in the subject to be imaged; b) comparing the error signature vector with the error candidate vector to identify specific attenuation signals in the set of attenuation signals that require correction; and c) correcting the identified attenuation signals.
Claim 3
Dependent Claim
24 words
The method as recited in claim 1 in which the correction of identified attenuation signals is performed using values from said error candidate vector.
Claim 4
Dependent Claim
24 words
The method as recited in claim 1 in which the correction of identified attenuation signals is performed using values from the error signature vector.
Claim 5
Dependent Claim
25 words
The method as recited in claim 3 in which the correction of identified attenuation signals is also performed using values from the error candidate vector.
Claim 6
Dependent Claim
40 words
The method as recited in claim 1 in which the reference phantom is a rod that has its lengthwise dimension disposed in the plane of the fan beam and which is constructed to variably attenuate x-rays along the thickness direction.
Claim 7
Dependent Claim
13 words
The method as recited in claim 5 in which the rod is tapered.
Claim 8
Dependent Claim
62 words
The method as recited in claim 1 in which the reference phantom is a circular disc disposed in the plane of the fan beam and the error signature vector is produced by averaging corresponding values in a plurality of sets of attenuation signals acquired by passing the fan beam of x-rays through the circular disc from a corresponding plurality of different angles.
Claim 9
Dependent Claim
18 words
The method as recited in claim 7 in which the circular edge of the circular disc is tapered.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-04-04 | 1997-10-04 | 1998-04-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-04-04 | 2001-10-04 | 2002-04-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-04-04 | 2005-10-04 | 2006-04-05 | $7700.00 | Window Closed / Lapsed |