US5090037A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Helical scanning computed tomography with tracking x-ray source
Assignee: General Electric Co
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Filing: 1990-11-19
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Granted: 1992-02-18
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Expires: 2010-11-19
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.
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 21:31
CPC Classifications
G; G21; G21K; G21K5/00; G21K5/10; A; A61; A61B; A61B6/00; A61B6/02; A61B6/027; G21K1/00; G21K1/02; G21K1/025
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
138 words
A method of acquiring tomographic projection data of an imaged object comprising: supporting and translating the imaged object concurrently along a translation axis; projecting a beam of x-rays from an x-ray generator through the imaged object and alternately sweeping the beam along the translation axis in a first direction with translation of the imaged object during a first period, and in a second direction along the translation axis but counter to the translation of the imaged object during a second period; receiving the beam from the x-ray generator with an x-ray detector array after it passes through the imaged object; and holding the x-ray generator and x-ray detector in opposition around the imaged body and concurrently rotating the same around a center of rotation and the imaged object, in an gantry plane substantially perpendicular to the translation axis.
Claim 2
Independent Claim
138 words
A method of acquiring tomographic projection data of an imaged object comprising: supporting and translating the imaged object concurrently along a translation axis; projecting a beam of x-rays from an x-ray generator through the imaged object and alternately sweeping the beam along the translation axis in a first direction with translation of the imaged object during a first period, and in a second direction along the translation axis but counter to the translation of the imaged object during a second period; receiving the beam from the x-ray generator with an x-ray detector array after it passes through the imaged object; and holding the x-ray generator and x-ray detector in opposition around the imaged body and concurrently rotating the same around a center of rotation and the imaged object, in an gantry plane substantially perpendicular to the translation axis.
Claim 3
Dependent Claim
41 words
The method as recited in claim 1 wherein the x-ray exposure of the imaged object by the x-ray beam during the first period is greater than the x-ray exposure of the imaged object by the x-ray beam during the second period.
Claim 4
Dependent Claim
20 words
The method as recited in claim 2 wherein the intensity of the x-ray beam is reduced during the second period.
Claim 5
Dependent Claim
35 words
The method as recited in claim 1 wherein the sweeping of the x-ray beam during the first period is such as to maintain the beam centered on a predetermined volume element on the translation axis.
Claim 6
Dependent Claim
26 words
The method recited in claim 4 wherein the x-ray generator comprises: a fixed x-ray source; and a collimator having an aperture movable along the translation axis.
Claim 7
Dependent Claim
83 words
The method recited in claim 5 wherein the aperture of the collimator is controlled according to the following equation: ##EQU5## where V z is the distance along the translation axis between the predetermined volume element and the gantry plane; C z is the distance along the translation axis between the center of the collimator and the gantry plane; l 1 is the distance between the x-ray source and the collimator; and l 2 is the distance between the collimator and the translation axis.
Claim 8
Dependent Claim
134 words
The method recited in claim 5 wherein the aperture of the collimator is controlled according to the following equation gantry angle θ as follows: ##EQU6## where l.sub.2 '=l.sub. -cos(θ+α) (Δ) and where θ is the gantry angle; V z is the distance along the translation axis between the predetermined volume element and the gantry plane; C z is the distance along the translation axis between the center of the collimator and the gantry plane; α is the angle, with respect to the center of rotation, between the volume of interest and gantry angle θ=O; Δ is the distance between the volume of interest and the center of gantry rotation; l 1 is the distance between the x-ray source and the collimator; and l 2 is the distance between the collimator and the translation axis.
Claim 9
Dependent Claim
33 words
The method recited in claim 4 wherein the x-ray generator comprises an x-ray source having a focal point movable along the translation axis and collimator having a aperture movable along the translation axis.
Claim 10
Dependent Claim
115 words
The method recited in claim 8 wherein the focal point and aperture of the collimator are controlled according to the following equations: ##EQU7## where V z is the distance along the translation axis between the predetermined volume element and the gantry plane; F z is the distance along the translation axis between x-ray source and the gantry plane; C z is the distance along the translation axis between the center of the collimator and the gantry plane; l 1 is the distance between the x-ray source and the collimator; l 2 is the distance between the collimator and the translation axis; and l 3 is the distance between the translation axis and the x-ray detector.
Claim 11
Dependent Claim
167 words
The method recited in claim 8 wherein the focal point and the aperture of the collimator are controlled according to the following equations: ##EQU8## where l.sub.2 '=l.sub.2 -cos(74 +α) (Δ) l.sub.3 '=l.sub.3 +cos(θ+α) (Δ) and where θ is the gantry angle; α is the angle, with respect to the center of rotation, between the volume of interest and gantry angle θ=O; Δ is the distance between the volume of interest and the center of gantry rotation; V z is the distance along the translation axis between the predetermined volume element and the gantry plane; F z is the distance along the translation axis between x-ray source and the gantry plane; C z is the distance along the translation axis between the center of the collimator and the gantry plane; l 1 is the distance between the x-ray source and the collimator; l 2 is the distance between the collimator and the translation axis; and l 3 is the distance between the translation axis and the x-ray detector.
Claim 12
Dependent Claim
81 words
The method recited in claim 8 wherein the focal point and the aperture of the collimator are controlled according to the following equation: F.sub.z =C.sub.z =V.sub.z where V z is the distance along the translation axis between the predetermined volume element and the gantry plane; F z is the distance along the translation axis between x-ray source and the gantry plane; and C z is the distance along the translation axis between the center of the collimator and the gantry plane.
Claim 13
Dependent Claim
27 words
The method recited in claim 4 wherein the x-ray generator comprises an x-ray source having a focal point movable along translation axis and a fixed collimator aperture.
Claim 14
Dependent Claim
78 words
The method recited in claim 12 wherein the focal point is controlled according to the following equation: ##EQU9## where F z is the distance along the translation axis between x-ray source and the gantry plane; V z is the distance along the translation axis between the predetermined volume element and the gantry plane; l 1 is the distance between the x-ray source and the collimator; and l 2 is the distance between the collimator and the translation axis.
Claim 15
Dependent Claim
124 words
The method recited in claim 10 wherein the focal point is controlled according to the following equation: ##EQU10## where l.sub.2 '=l.sub.2 -cos(θ+α) (Δ) and where θ is the gantry angle; α is the angle, with respect to the center of rotation, between the volume of interest and gantry angle θ=O; Δ is the distance between the volume of interest and the center of gantry rotation; F z is the distance along the translation axis between x-ray source and the gantry plane; V z is the distance along the translation axis between the predetermined volume element and the gantry plane; l 1 is the distance between the x-ray source and the collimator; and l 2 is the distance between the collimator and 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) | 1995-02-17 | 1995-08-19 | 1996-02-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-02-17 | 1999-08-19 | 2000-02-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-02-17 | 2003-08-19 | 2004-02-18 | $7700.00 | Window Closed / Lapsed |