US6651018B2
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Method for correcting calibration values in a calibration table of computed tomography apparatus
Assignee: Siemens AG
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Filing: 2002-03-05
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Granted: 2003-11-18
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Expires: 2022-03-05
Abstract
Abstract In a method for correcting a calibration table T(n,k) of a CT apparatus that contains calibration values, the CT apparatus having a detector system with N>=2 rows of detector elements following one another in the z-direction that include a first active row of detector elements in the z-direction and a last active row of detector elements in the z-direction, for correcting the calibration values of the aforementioned first and last active rows of detector elements, a reference vector R(k) is produced, the error is determined with respect to the first and last active rows of detector elements, and the error F(n,k) of the first and last active rows of detector elements is subtracted from the corresponding calibration values of the calibration table T(n,k) for determining corrected calibration values Tcor(n,k) with respect to the first and last active rows of detector elements.
Inventors
- 👤 Helmut Kropfeld
- 👤 Karl Schwarz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 14:55
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/58; A61B6/582; A61B6/585; A61B6/02; A61B6/03; A61B6/032; G; G01; G01N; G01N23/00; G01N23/02; G01N23/04; G01N23/046; G01T; G01T1/00; G01T1/29; G01T1/2914; G01T1/2985; A61B6/06; G01N2223/00; G01N2223/40; G01N2223/419; Y; Y10; Y10S; Y10S378/00; Y10S378/901
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
150 words
A method for correcting a calibration table T(n,k) of a computed tomography apparatus wherein n is a row index of a detector system of the apparatus and k is a channel index of the detector system, said detector system comprising a plurality N≧2 of active rows of detector elements following one another in a z-direction that includes outer active rows comprising at least a first active row of detector elements in the z-direction and a last active row of detector elements in the z-direction, comprising the steps, for correcting the calibration values of the outer active rows of detector elements, of: producing a reference vector R(k); determining an error F(n,k)=T(n,k)−R(k) for the outer active rows, and subtracting the error F(n,k) for the outer active rows from calibration values of the calibration table T(n,k) for said outer rows to determine corrected calibration values T cor (n,k) for the outer active rows.
Claim 2
Independent Claim
150 words
A method for correcting a calibration table T(n,k) of a computed tomography apparatus wherein n is a row index of a detector system of the apparatus and k is a channel index of the detector system, said detector system comprising a plurality N≧2 of active rows of detector elements following one another in a z-direction that includes outer active rows comprising at least a first active row of detector elements in the z-direction and a last active row of detector elements in the z-direction, comprising the steps, for correcting the calibration values of the outer active rows of detector elements, of: producing a reference vector R(k); determining an error F(n,k)=T(n,k)−R(k) for the outer active rows, and subtracting the error F(n,k) for the outer active rows from calibration values of the calibration table T(n,k) for said outer rows to determine corrected calibration values T cor (n,k) for the outer active rows.
Claim 3
Dependent Claim
31 words
A method according to claim 1 , comprising low pass filtering the error F(n,k) for the outer active rows before the subtraction from the calibration values of the calibration table T(n,k).
Claim 4
Dependent Claim
61 words
A method according to claim 1 wherein N>2 and comprising producing R ( k ) = 1 ( N - 2 ) ∑ n = 2 N - 1 ( T ( n , k ) ) as said reference vector for determining the error of the respective outermost active rows n=1 and n=N in the z-direction.
Claim 5
Dependent Claim
64 words
A method according to claim 1 wherein N>2 and comprising: producing R(k)=T(n+1,k) as said reference vector for determining the error for the outermost active row n=1 at one side of the detector system, in the z-direction: and producing R(k)=T(N−1,k) as said reference vector for determining the error for the outermost active row n=N at an opposite side of said detector system in the z-direction.
Claim 6
Dependent Claim
121 words
A method according to claim 1 wherein N>2 and comprising: producing R ( k ) = 1 u ∑ n = 2 u + 1 ( T ( n , k ) ) as said reference vector for determining the error for the outermost active row n=1 at one side of the detector system in the z-direction; and producing R ( k ) = 1 u ∑ n = N - u N - 1 ( T ( n , k ) ) n=N at an opposite side of the detector system in the z-direction wherein u is a number of inner active rows of said detector system between said outermost active rows.
Claim 7
Dependent Claim
61 words
A method according to claim 1 wherein N>2 and comprising: producing R ( k ) = 1 2 ( T ( n + 1 , k ) + T ( N - 1 , k ) ) as said reference vector for determining the error of the respective outermost active rows n=1 and n=N in the z-direction.
Claim 8
Dependent Claim
93 words
A method according to claim 1 wherein N>2 and comprising: producing R ( k ) = 1 2 ( 1 ( N - 2 ) ∑ n = 2 u + 1 ( T ( n , k ) ) + 1 ( N - 2 ) ∑ n = N - n N - 1 ( T ( n , k ) ) ) as said reference vector for determining the error of the respective outermost active rows n=1 and n=N in the z-direction.
Claim 9
Dependent Claim
56 words
A method according to claim 1 wherein N>2 comprising: producing R ( k ) = 1 2 ( T ( 1 , k ) + T ( 2 , k ) ) as said reference vector for determining the error of the respective outermost active rows n=1 and n=N in the z-direction.
Claim 10
Dependent Claim
30 words
A method according to claim 1 , comprising correcting calibration values at opposite sides of said detector system in the z-direction for respective pluralities q of outer rows, with q≧1.
Claim 11
Dependent Claim
67 words
A method according to claim 9 , comprising: producing R ( k ) = 1 ( N - 2 q ) ∑ n = 1 + q N - q ( T ( n , k ) ) as respective reference vectors for determining the error of the respective outermost active lines n=1 through n=q and n=N−q+1 through n=N in the z-direction.
Claim 12
Dependent Claim
33 words
A method according to claim 9 comprising identically weighting the reference vectors R(k) for determining the error of the respectively outermost active lines n=1 through n=q and n=N−q+1 through n=N in the z-direction.
Claim 13
Dependent Claim
33 words
A method according to claim 9 comprising differently weighting the reference vectors R(k) for determining the error of the respectively outermost active lines n=1 through n=q and n=N−q+1 through n=N in the z-direction.
Claim 14
Dependent Claim
54 words
A method according to claim 12 , wherein the step of differently weighting the respective reference vectors R(k) for determining the error of the respective outermost active lines n=1 through n=q and n=N−q+1 through n=N in the z-direction comprises weighting the respective vectors R(k) increasingly higher from inside to outside of said detector system.
References Cited (Backward Citations)
US6163759A
Cited
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