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US6134292A
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Methods and apparatus for reducing z-axis non-uniformity artifacts
Assignee: General Electric Co
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Filing: 1998-07-13
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Granted: 2000-10-17
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Expires: 2018-07-13
Abstract
Abstract Methods and apparatus of correcting image data for z-axis non-uniformity in a computed tomography (CT) system are described. In one embodiment, the CT system includes a configurable multislice detector array and a calibration algorithm. In accordance with one embodiment of the algorithm, output signals from a plurality of detector cells are sampled to generate an x-ray beam z-axis non-uniformity profile. The x-ray beam z-axis profile is then used to determine a detector z-axis non-uniformity profile for the detector array. Utilizing the z-axis profiles, the output signals from the detector cells may be calibrated to reduce z-axis non-uniformity errors.
Inventors
- 👤 Jiang Hsieh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 15:47
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/44; A61B6/4411; A61B6/02; A61B6/03; A61B6/032; A61B6/40; A61B6/4064; A61B6/4085; G; G01; G01T; G01T1/00; G01T1/29; G01T1/2914; G01T1/2985; Y; Y10; Y10S; Y10S378/00; Y10S378/901
Claims Analysis
Total Claims: 56
Claim 1
Independent Claim
143 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said system being configured to: determine an x-ray beam z-axis profile; and determine a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein: said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to obtain signals from a select number of detector cells in at least one channel of the detector array; and said system being configured to obtain signals from a selected number of detector cells comprises said system being configured to select at least one detector cell having a uniform gain measurement.
Claim 2
Independent Claim
143 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said system being configured to: determine an x-ray beam z-axis profile; and determine a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein: said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to obtain signals from a select number of detector cells in at least one channel of the detector array; and said system being configured to obtain signals from a selected number of detector cells comprises said system being configured to select at least one detector cell having a uniform gain measurement.
Claim 3
Independent Claim
91 words
A method for calibrating projection data in a multi-slice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, and the detector array cells are arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile including obtaining signals from detector cells in at least one fully sampled channel of the detector array; and determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile.
Claim 4
Independent Claim
91 words
A method for calibrating projection data in a multi-slice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, and the detector array cells are arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile including obtaining signals from detector cells in at least one fully sampled channel of the detector array; and determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile.
Claim 5
Dependent Claim
15 words
A method in accordance with claim 2 wherein each channel comprises a plurality of slices.
Claim 6
Dependent Claim
38 words
A method in accordance with claim 3 wherein determining an x-ray beam z-axis profile comprises fully sampling a plurality of channels and interpolating signals from the fully-sampled channels to estimate an x-ray beam z-axis profile for non-fully-sampled channels.
Claim 7
Dependent Claim
28 words
A method in accordance with claim 2 further comprising the step of determining a gain profile for each of the selected detector cells to determine detector gain profiles.
Claim 8
Dependent Claim
25 words
A method in accordance with claim 2 further comprising the step of adjusting the projection data using the detector gain profiles and x-ray flux profiles.
Claim 9
Dependent Claim
26 words
A method in accordance with claim 6 wherein adjusting projection data comprises the step of generating a gain profile for each detector cell not fully sampled.
Claim 10
Dependent Claim
34 words
A method in accordance with claim 7 wherein generating a gain profile for each non-fully-sampled detector cell comprises the step of determining a measured output signal, wherein the measured output signal, y', is: ##EQU4##
Claim 11
Dependent Claim
31 words
A method in accordance with claim 8 wherein generating the true x-ray flux for each non-fully-sampled detector cell further comprises the step of determining a true x-ray flux for the channel.
Claim 12
Dependent Claim
16 words
A method in accordance with claim 9 wherein the true x-ray flux for the channel is:
Claim 13
Dependent Claim
38 words
A method in accordance with claim 10 wherein each slice channel comprises four cells and wherein the measured output signal for each slice of each non-fully-sampled detector cell is: y'=g'.sub.0 α'.sub.0 l'+g'.sub.1 α'.sub.1 l'+g'.sub.2 α'.sub.2 l'+g'.sub.3 α'.sub.3 l'.
Claim 14
Dependent Claim
17 words
A method in accordance with claim 10 wherein the true x-ray flux for the channel is: ##EQU5##
Claim 15
Dependent Claim
33 words
A method in accordance with claim 12 wherein generating the x-ray flux profile for the non-fully-sampled detector cells comprises the step of creating a polynomial fit of the fully-sampled detector cell output signals.
Claim 16
Dependent Claim
48 words
A method in accordance with claim 2 wherein obtaining signals from detector cells in at least one fully sampled channel of the detector array further comprises the steps of: generating view data utilizing the detector cell signals; and generating the true x-ray flux profile utilizing the view data.
Claim 17
Dependent Claim
51 words
A method in accordance with claim 2 wherein obtaining signals from detector cells in at least one fully sampled channel of the detector array further comprises the steps of: generating data for multiple views utilizing the detector cell signals; and generating the true x-ray flux profile utilizing the multiple view data.
Claim 18
Dependent Claim
40 words
A method in accordance with claim 2 wherein obtaining signals from detector cells in at least one fully sampled channel of the detector array further comprises the step of selecting at least one detector cell having an uniform gain measurement.
Claim 19
Dependent Claim
43 words
A method in accordance with claim 2 wherein determining an x-ray beam z-axis profile comprises the steps of: estimating an x-ray flux profile; adjusting the output signals of each channel; and generating a revised x-ray beam z-axis profile utilizing the adjusted output signals.
Claim 20
Independent Claim
153 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said system being configured to: determine an x-ray beam z-axis profile; and determine a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein: said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to obtain signals from a select number of detector cells in at least one channel of the detector array; said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to: estimate an x-ray flux profile; adjust the output signals of each channel; and generate a revised x-ray beam z-axis profile utilizing the adjusted output signals.
Claim 21
Independent Claim
153 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said system being configured to: determine an x-ray beam z-axis profile; and determine a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein: said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to obtain signals from a select number of detector cells in at least one channel of the detector array; said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to: estimate an x-ray flux profile; adjust the output signals of each channel; and generate a revised x-ray beam z-axis profile utilizing the adjusted output signals.
Claim 22
Independent Claim
107 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, wherein said detector cell columns are arranged in channels said system configured to: determine at least one z-axis x-ray beam profile; and determine a true x-ray flux utilizing detector gain profiles and said determined x-ray beam profile; and wherein to determine said x-ray beam profile, said system is configured to obtain signals from a select number of detector cells in at least one channel of said detector array.
Claim 23
Independent Claim
107 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, wherein said detector cell columns are arranged in channels said system configured to: determine at least one z-axis x-ray beam profile; and determine a true x-ray flux utilizing detector gain profiles and said determined x-ray beam profile; and wherein to determine said x-ray beam profile, said system is configured to obtain signals from a select number of detector cells in at least one channel of said detector array.
Claim 24
Dependent Claim
15 words
A system in accordance with claim 19 wherein each channel comprises a plurality of slices.
Claim 25
Dependent Claim
49 words
A system in accordance with claim 20 wherein said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to fully sample a plurality of channels and to interpolate signals from the fully-sampled channels to estimate an x-ray beam z-axis profile for non-fully-sampled channels.
Claim 26
Dependent Claim
24 words
A system in accordance with claim 19, said system being further configured to determine a gain profile for each of said selected detector cells.
Claim 27
Dependent Claim
23 words
A system in accordance with claim 19 further configured to adjust the projection data using said detector gain profiles and said x-ray flux.
Claim 28
Dependent Claim
29 words
A system in accordance with claim 23 wherein to adjust the projection data, said system is configured to generate a gain profile for each detector cell not fully sampled.
Claim 29
Dependent Claim
36 words
A system in accordance with claim 24 wherein to generate a gain profile for each non-fully-sampled detector cell, said system is configured to determine a measured output signal, wherein said measured output signal, y', is: ##EQU6##
Claim 30
Dependent Claim
32 words
A system in accordance with claim 25 wherein to generate said true x-ray flux for each non-fully-sampled detector cell, said system is configured to determine a true x-ray flux for said channel.
Claim 31
Dependent Claim
16 words
A system in accordance with claim 26 wherein said true x-ray flux for said channel is:
Claim 32
Dependent Claim
38 words
A system in accordance with claim 27 wherein each slice channel comprises four cells and wherein said measured output signal for each slice of each non-fully-sampled detector cell is: y'=g'.sub.0 α'.sub.0 l'+g'.sub.1 α'.sub.1 l'+g'.sub.2 α'.sub.2 l'+g'.sub.3 α'.sub.3 l'.
Claim 33
Dependent Claim
17 words
A system in accordance with claim 27 wherein said true x-ray flux for said channel is: ##EQU7##30.
Claim 34
Dependent Claim
35 words
A system in accordance with claim 29 wherein to generate said x-ray flux profile for said non-fully-sampled detector cells, said system is configured to create a polynomial fit of said fully-sampled detector cell output signals.
Claim 35
Dependent Claim
50 words
A system in accordance with claim 19 wherein to obtain signals from detector cells in at least one fully sampled channel of the detector array, said system is further configured to: generate view data utilizing said detector cell signals; and generate said true x-ray flux profile utilizing said view data.
Claim 36
Dependent Claim
53 words
A system in accordance with claim 19 wherein to obtain signals from detector cells in at least one fully sampled channel of the detector array, said system is further configured to: generate data for multiple views utilizing said detector cell signals; and generate said true x-ray flux profile utilizing said multiple view data.
Claim 37
Dependent Claim
42 words
A system in accordance with claim 19 wherein to obtain signals from detector cells in at least one fully sampled channel of the detector array, said system is further configured to select at least one detector cell having an uniform gain measurement.
Claim 38
Dependent Claim
45 words
A system in accordance with claim 19 wherein to determine an x-ray beam z-axis profile, said system is configured to: estimate an x-ray flux profile; adjust said output signals of each channel; and generate a revised x-ray beam z-axis profile utilizing said adjusted output signals.
Claim 39
Independent Claim
118 words
A method for calibrating projection data in a multislice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile, including obtaining signals from a select number of detector cells in at least one channel of the detector array; and determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein obtaining signals from a selected number of detector cells comprises the step of selecting at least one detector cell having a uniform gain measurement.
Claim 40
Independent Claim
118 words
A method for calibrating projection data in a multislice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile, including obtaining signals from a select number of detector cells in at least one channel of the detector array; and determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein obtaining signals from a selected number of detector cells comprises the step of selecting at least one detector cell having a uniform gain measurement.
Claim 41
Independent Claim
129 words
A method for calibrating projection data in a multislice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile, including obtaining signals from a select number of detector cells in at least one channel of the detector array; and determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein determining an x-ray beam z-axis profile comprises the steps of: estimating an x-ray flux profile; adjusting the output signals of each channel; and generating a revised x-ray beam z-axis profile utilizing the adjusted output signals.
Claim 42
Independent Claim
129 words
A method for calibrating projection data in a multislice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile, including obtaining signals from a select number of detector cells in at least one channel of the detector array; and determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; wherein determining an x-ray beam z-axis profile comprises the steps of: estimating an x-ray flux profile; adjusting the output signals of each channel; and generating a revised x-ray beam z-axis profile utilizing the adjusted output signals.
Claim 43
Independent Claim
143 words
A method for calibrating projection data in a multislice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile including obtaining signals from a select number of detector cells in at least one channel of the detector array; determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; adjusting the projection data using the detector gain profiles and the determined x-ray flux profiles, including generating a gain profile for each non-selected detector cell; wherein generating a gain profile for each non-selected detector cell comprises the step of determining a measured output signal, wherein the measured output signal, y', is: ##EQU8##
Claim 44
Independent Claim
143 words
A method for calibrating projection data in a multislice computed tomography system, the system including an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells arranged in channels, said method comprising the steps of: determining an x-ray beam z-axis profile including obtaining signals from a select number of detector cells in at least one channel of the detector array; determining a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; adjusting the projection data using the detector gain profiles and the determined x-ray flux profiles, including generating a gain profile for each non-selected detector cell; wherein generating a gain profile for each non-selected detector cell comprises the step of determining a measured output signal, wherein the measured output signal, y', is: ##EQU8##
Claim 45
Dependent Claim
31 words
A method in accordance with claim 37 wherein generating the true x-ray flux for each non-selected detector cell further comprises the step of determining a true x-ray flux for the channel.
Claim 46
Dependent Claim
16 words
A method in accordance with claim 38 wherein the true x-ray flux for the channel is:
Claim 47
Dependent Claim
38 words
A method in accordance with claim 39 wherein each slice channel comprises four cells and wherein the measured output signal for each slice of each non-selected detector cell is: y'=g'.sub.0 α'.sub.0 l'+g'.sub.1 α'.sub.1 l'+g'.sub.2 α'.sub.2 l'+g'.sub.3 α'.sub.3 l'.
Claim 48
Dependent Claim
17 words
A method in accordance with claim 39 wherein the true x-ray flux for the channel is: ##EQU9##
Claim 49
Dependent Claim
33 words
A method in accordance with claim 41 wherein generating the x-ray flux profile for the non-selected detector cells comprises the step of creating a polynomial fit of the selected detector cell output signals.
Claim 50
Independent Claim
183 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said system configured to: determine an x-ray beam z-axis profile; determine a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; and adjust the projection data using the detector gain profiles and the determined x-ray flux profiles; wherein: said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to obtain signals from a select number of detector cells in at least one channel of the detector array; said system being configured to adjust the projection data includes said system being configured to generate a gain profile for each non-selected detector cell; and said system being configured to generate a gain profile for each non-selected detector cell comprises said system being configured to determine a measured output signal, wherein the measured output signal, y', is: ##EQU10##
Claim 51
Independent Claim
183 words
A system for calibrating projection data for generating a tomographic image of an object, said system comprising an x-ray source and a detector array comprising a plurality of cells arranged in rows and columns and displaced along a z-axis, the detector array column cells being arranged in channels, said system configured to: determine an x-ray beam z-axis profile; determine a true x-ray flux utilizing detector gain profiles and the determined x-ray beam profile; and adjust the projection data using the detector gain profiles and the determined x-ray flux profiles; wherein: said system being configured to determine an x-ray beam z-axis profile comprises said system being configured to obtain signals from a select number of detector cells in at least one channel of the detector array; said system being configured to adjust the projection data includes said system being configured to generate a gain profile for each non-selected detector cell; and said system being configured to generate a gain profile for each non-selected detector cell comprises said system being configured to determine a measured output signal, wherein the measured output signal, y', is: ##EQU10##
Claim 52
Dependent Claim
37 words
A system in accordance with claim 43 wherein said system being configured to generate the true x-ray flux for each non-selected detector cell comprises said system being configured to determine a true x-ray flux for the channel.
Claim 53
Dependent Claim
16 words
A system in accordance with claim 44 wherein the true x-ray flux for the channel is:
Claim 54
Dependent Claim
38 words
A system in accordance with claim 45 wherein each slice channel comprises four cells and wherein the measured output signal for each slice of each non-selected detector cell is: y'=g'.sub.0 α'.sub.0 l'+g'.sub.1 α'.sub.1 l'+g'.sub.2 α'.sub.2 l'+g'.sub.3 α'.sub.3 l'.
Claim 55
Dependent Claim
17 words
A system in accordance with claim 45 wherein the true x-ray flux for the channel is: ##EQU11##
Claim 56
Dependent Claim
40 words
A system in accordance with claim 47 wherein said system being configured to generate the x-ray flux profile for the non-selected detector cells comprises said system being configured to create a polynomial fit of the selected detector cell output signals.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2003-10-17 | 2004-04-17 | 2004-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-10-17 | 2008-04-17 | 2008-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-10-17 | 2012-04-17 | 2012-10-17 | $7700.00 | Window Closed / Lapsed |