US5379333A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable dose application by modulation of x-ray tube current during CT scanning
Assignee: General Electric Co
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Filing: 1993-11-19
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Granted: 1995-01-03
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Expires: 2013-11-19
Abstract
Abstract An x-ray CT system modulates x-ray tube current as a function of gantry angle to reduce the total patient dose without significantly increasing image noise. A scout scan is performed to acquire attenuation data which enables an optimal current modulation profile to be calculated for each slice in the scan.
Inventors
- 👤 Thomas L. Toth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 23:34
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/48; A61B6/488; A61B6/02; A61B6/03; A61B6/032; A61B6/54; A61B6/542; H; H05; H05G; H05G1/00; H05G1/08; H05G1/26; H05G1/60
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
120 words
A method for reducing the dose of an x-ray beam applied to a patient by an x-ray CT system during the acquisition of attenuation data from a single slice as a gantry rotates around the patient, the steps comprising: acquiring patient projection data from the slice which indicates patient attenuation of the x-ray beam at two substantially orthogonal gantry angles; calculating a modulation profile using information derived from the acquired patient projection data, the modulation profile indicating the x-ray dose to be applied to the patient as a function of gantry angle; and acquiring the attenuation data for the single slice by rotating the gantry around the patient and modulating the applied x-ray dose as indicated by the modulation profile.
Claim 2
Independent Claim
120 words
A method for reducing the dose of an x-ray beam applied to a patient by an x-ray CT system during the acquisition of attenuation data from a single slice as a gantry rotates around the patient, the steps comprising: acquiring patient projection data from the slice which indicates patient attenuation of the x-ray beam at two substantially orthogonal gantry angles; calculating a modulation profile using information derived from the acquired patient projection data, the modulation profile indicating the x-ray dose to be applied to the patient as a function of gantry angle; and acquiring the attenuation data for the single slice by rotating the gantry around the patient and modulating the applied x-ray dose as indicated by the modulation profile.
Claim 3
Dependent Claim
23 words
The method as recited in claim 1 in which the x-ray dose is modulated by changing the current supplied to the x-ray tube.
Claim 4
Dependent Claim
44 words
The method as recited in claim 1 in which the modulation profile varies the x-ray dose substantially sinusoidally as a function of gantry angle, and the info,nation derived from the patient projection data is a modulation index which indicates the magnitude of the variations.
Claim 5
Dependent Claim
30 words
The method as recited in claim 3 in which the modulation index is derived by calculating the ratio of patient projection data acquired at said two substantially orthogonal gantry angles.
Claim 6
Dependent Claim
25 words
The method as recited in claim 3 in which the shape of the modulation profile is changed when the modulation index exceeds a preset amount.
Claim 7
Dependent Claim
49 words
The method as recited in claim 3 in which the modulation index is derived by calculating the ratio of patient projection data acquired at said two substantially orthogonal gantry angles and using said ratio to read the modulation index from a table storing a plurality of different modulation indices.
Claim 8
Independent Claim
83 words
A method for reducing the dose of an x-ray beam applied to a patient by an x-ray CT system during the acquisition of attenuation data from a single slice, the steps comprising: storing a modulation profile which indicates variations in x-ray beam intensity as a function of gantry angle during the acquisition of attenuation data; modulating an x-ray tube operating parameter using values stored in the modulation profile; and acquiring a slice of attenuation data while the x-ray tube operating parameter is modulated.
Claim 9
Independent Claim
83 words
A method for reducing the dose of an x-ray beam applied to a patient by an x-ray CT system during the acquisition of attenuation data from a single slice, the steps comprising: storing a modulation profile which indicates variations in x-ray beam intensity as a function of gantry angle during the acquisition of attenuation data; modulating an x-ray tube operating parameter using values stored in the modulation profile; and acquiring a slice of attenuation data while the x-ray tube operating parameter is modulated.
Claim 10
Dependent Claim
17 words
The method as recited in claim 7 in which the x-ray tube operating parameter is tube current.
Claim 11
Dependent Claim
54 words
The method as recited in claim 7 in which the modulation profile is shaped to reduce the x-ray dose while the gantry is oriented to position the x-ray tube directly over the patient's eyes, and to increase the x-ray dose when the x-ray tube is positioned directly over the back of the patient's head.
References Cited (Backward Citations)
US4624007A
Cited
US5103469A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-01-02 | 1998-07-04 | 1999-01-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-01-02 | 2002-07-04 | 2003-01-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-01-02 | 2006-07-04 | 2007-01-03 | $7700.00 | Window Closed / Lapsed |