US5224136A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Helical scanning computed tomography apparatus with constrained tracking of the x-ray source
Assignee: General Electric Co
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Filing: 1992-06-30
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Granted: 1993-06-29
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Expires: 2012-06-30
Abstract
Abstract A CT apparatus reduces errors in projection data acquired in helical scanning. The imaged object moves concurrently along a translation axis and the x-ray beam is periodically translated with the imaged object so as to subtend a single predetermined volume element during the acquisition of one projection set of data for a first slice. The x-ray beam then returns to its starting position and tracks a second predetermined volume element within a next slice. The x-ray beam may be translated by moving the focal point or a collimator or a combination of both. Helical scans with a pitch requiring sweeping of the x-ray beam beyond the detector limits are accommodated by limiting the sweep to a lessor compliance distance. The angular rate of the sweep is held constant within this compliance distance during the sweep.
Inventors
- 👤 Thomas L. Toth
- 👤 Kevin F. King
- 👤 Carl R. Crawford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 20:52
CPC Classifications
G; G21; G21K; G21K5/00; G21K5/10; A; A61; A61B; A61B6/00; A61B6/02; A61B6/027; G21K1/00; G21K1/02; G21K1/04; G21K1/043
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
191 words
An apparatus for acquiring a tomographic projection set of an imaged object, the apparatus comprising: an x-ray generator for projecting a beam of x-rays through the imaged object at a plurality of angles about the imaged object gantry plane substantially perpendicular to a translation axis; an x-ray detector opposing the x-ray generator through the imaged object for receiving the x-ray beam at the plurality of angles to create a projection set; a table for supporting and translating the imaged object by a translation distance along a translation axis with the acquisition of the projection set during a first period, the translation being concurrent with the projections of the plurality of angles; a means for alternately sweeping the beam by a predetermined compliance distance along the translation axis in a first direction during the first period, and in a second direction along the translation axis but counter to the translation of the imaged object during a second period, wherein the compliance distance is limited to less than the translation distance and wherein the beam of x-rays is received by the x-ray detector throughout the sweeping of the beam by the compliance distance.
Claim 2
Independent Claim
191 words
An apparatus for acquiring a tomographic projection set of an imaged object, the apparatus comprising: an x-ray generator for projecting a beam of x-rays through the imaged object at a plurality of angles about the imaged object gantry plane substantially perpendicular to a translation axis; an x-ray detector opposing the x-ray generator through the imaged object for receiving the x-ray beam at the plurality of angles to create a projection set; a table for supporting and translating the imaged object by a translation distance along a translation axis with the acquisition of the projection set during a first period, the translation being concurrent with the projections of the plurality of angles; a means for alternately sweeping the beam by a predetermined compliance distance along the translation axis in a first direction during the first period, and in a second direction along the translation axis but counter to the translation of the imaged object during a second period, wherein the compliance distance is limited to less than the translation distance and wherein the beam of x-rays is received by the x-ray detector throughout the sweeping of the beam by the compliance distance.
Claim 3
Dependent Claim
54 words
The apparatus as recited in claim 1 including additionally an exposure controller for controlling the exposure of the imaged object by the x-ray beam during the first period so that the exposure during the first period is greater than the x-ray exposure of the imaged object by the x-ray beam during a second period.
Claim 4
Dependent Claim
22 words
The apparatus as recited in claim 2 wherein the exposure controller reduces the intensity of the x-ray beam during the second period.
Claim 5
Dependent Claim
74 words
The apparatus as recited in claim 1 wherein the means for alternatively sweeping sweeps the x-ray beam during a first portion of the first period so as to maintain the beam centered on a predetermined volume element on the translation axis in the imaged object within the predetermined compliance distance and stops the sweeping of the x-ray beam during a second portion of the first period at the limit of the predetermined compliance distance.
Claim 6
Dependent Claim
23 words
The apparatus as recited in claim 4 wherein the first portion is divided equally between the start and end of the first period.
Claim 7
Dependent Claim
37 words
The apparatus as recited in claim 1 wherein the means for alternatively sweeping, sweeps of the x-ray beam during the first period so as to maintain a constant angular motion of the beam during the first period.
Claim 8
Dependent Claim
34 words
The apparatus recited in claim 1 wherein the means for alternatively sweeping comprises a collimator positioned between the x-ray generator and the imaged object, the collimator having an aperture movable along the translation axis.
Claim 9
Dependent Claim
35 words
The apparatus recited in claim 1 wherein the means for alternatively sweeping comprises an x-ray source having a focal point movable along the translation axis and collimator having a aperture movable along the translation axis.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-06-28 | 1996-12-28 | 1997-06-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-28 | 2000-12-28 | 2001-06-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-28 | 2004-12-28 | 2005-06-29 | $7700.00 | Window Closed / Lapsed |