EP0210038A2
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EP
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Chemical shift imaging with field inhomogeneity corrections
Assignee: Siemens AG
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Filing: 1986-07-15
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Granted: —
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Expires: 2006-07-15
Abstract
Abstract In an NMR system, two chemical shift components are separated by correcting NMR data for field inhomogeneity. A first image data set is acquired which contains no chemical shift information or field inhomogeneity. A second image data set is acquired which contains both chemical shift information and field inhomogeneity. A third image data set is acquired which contains field inhomogeneity information. The first and third image data sets are combined to identify the field inhomogeneity information. This intermediate field image is then used to correct the second image data set for field inhomogeneity. The first image data set and corrected second image data set may then be combined by magnitude reconstruction of complex sums and differences to separate the two chemical shift components.
Inventors
- 👤 Donald William Kormos
- 👤 Henry Samuel Dewhurst
- 👤 Hong-Ning Yeung
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 11:48
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/565; G01R33/56563; G01R33/483; G01R33/485
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
101 words
Apparatus for obtaining chemical shift information in an NMR environment comprising: means for obtaining a) a first data set of NMR signal information which contains virtually no chemical shift and magnetic field inhomogeneity information, b) a second data set of NMR signal information which contains chemical shift and field inhomogeneity information, and c) a third data set of NMR signal information which contains field inhomogeneity information; and means for combining the first and third data sets to identify the field inhomogeneity information and for combining the identified field inhomogeneity information with the second data set to identify the chemical shift information.
Claim 2
Dependent Claim
101 words
Apparatus for obtaining chemical shift information in an NMR environment comprising: means for obtaining a) a first data set of NMR signal information which contains virtually no chemical shift and magnetic field inhomogeneity information, b) a second data set of NMR signal information which contains chemical shift and field inhomogeneity information, and c) a third data set of NMR signal information which contains field inhomogeneity information; and means for combining the first and third data sets to identify the field inhomogeneity information and for combining the identified field inhomogeneity information with the second data set to identify the chemical shift information.
Claim 3
Dependent Claim
46 words
The apparatus of claim 1, wherein each data set may also contain an instrumentation error phase angle, and wherein the combining means is adapted to combinine the first and third data sets to identify the field inhomogeneity information and eliminate any common instrumentation error phase angle.
Claim 4
Dependent Claim
155 words
Apparatus for obtaining chemical shift information in an NMR environment comprising: means for obtaining a) a first data set of NM R signal information in which two chemical shift components are oriented at a first angle relative to each other and which contains virtually no magnetic field inhomogeneity information, b) a second data set of NMR signal information in which said two chemical shift components are oriented at a second angle relative to each other and which contains field inhomogeneity information, and c) a third data set of NMR signal information in which said two chemical shift components are oriented at said first angle relative to each other and which contains field inhomogeneity information; and means for combining the first and third data sets to identify the field inhomogeneity information; and for combining the identified field inhomogeneity information with the second data set to correct the second data set by eliminating the field inhomogeneity information.
Claim 5
Dependent Claim
155 words
Apparatus for obtaining chemical shift information in an NMR environment comprising: means for obtaining a) a first data set of NM R signal information in which two chemical shift components are oriented at a first angle relative to each other and which contains virtually no magnetic field inhomogeneity information, b) a second data set of NMR signal information in which said two chemical shift components are oriented at a second angle relative to each other and which contains field inhomogeneity information, and c) a third data set of NMR signal information in which said two chemical shift components are oriented at said first angle relative to each other and which contains field inhomogeneity information; and means for combining the first and third data sets to identify the field inhomogeneity information; and for combining the identified field inhomogeneity information with the second data set to correct the second data set by eliminating the field inhomogeneity information.
Claim 6
Dependent Claim
24 words
The apparatus of claim 3, wherein said first angle is substantially equal to zero radians, and said second angle is substantially equal to radians.
Claim 7
Independent Claim
80 words
The apparatus of any one of claims 1 to 4, further comprising means for reconstructing images using the three data sets; and wherein the combining means is adapted to combine the image data of the first and third data sets to form a field image which identifies the field inhomogeneity information and to combine the field image in combination with the image data of the second data set to form a corrected second image which eliminates the field inhomogeneity information.
Claim 8
Dependent Claim
46 words
The apparatus of claim 5, further comprising means for forming a complex sum of the image data of the first data set and the corrected second image; and for taking the magnitude of the complex sum to produce a magnitude image of one chemical shift component.
Claim 9
Dependent Claim
47 words
The apparatus of claim 5, further comprising means for forming a complex difference of the image data of the first data set and the corrected second image; and for taking the magnitude of the complex difference to produce a magnitude image of a second chemical shift component.
Claim 10
Dependent Claim
109 words
Apparatus for obtaining field inhomogeneity corrected NMR information in an NMR environment comprising: means for performing a first NMR multi-echo experiment to yield first and second data sets of NMR signal information, each with a characteristic set of instrument error terms, and a second NMR multi-echo experiment to yield third and fourth data sets of NMR signal information, each with a characteristic set of magnetic field inhomogeneity and instrumentation error terms; and means for combining said second and fourth data set to identify said field inhomogeneity terms; and for combining the identified field inhomogeneity terms with the third data set to correct the third data set for field inhomogeneities.
Claim 11
Dependent Claim
109 words
Apparatus for obtaining field inhomogeneity corrected NMR information in an NMR environment comprising: means for performing a first NMR multi-echo experiment to yield first and second data sets of NMR signal information, each with a characteristic set of instrument error terms, and a second NMR multi-echo experiment to yield third and fourth data sets of NMR signal information, each with a characteristic set of magnetic field inhomogeneity and instrumentation error terms; and means for combining said second and fourth data set to identify said field inhomogeneity terms; and for combining the identified field inhomogeneity terms with the third data set to correct the third data set for field inhomogeneities.
Claim 12
Dependent Claim
109 words
The apparatus of claim 8, wherein the means for performing is adapted to perform a) a first NMR multi-echo experiment to yield first and second data sets of NMR signal information, each with a characteristic set of instrumentation error terms, wherein said first data set contains two chemical shift components oriented at a first angle relative to each other; and b) a second NMR multi-echo experiment to yield third and fourth data sets of NMR signal information, each with a characteristic set of magnetic field inhomogeneity and instrumentation error terms, wherein said third data set contains two chemical shift components orieinted at a second angle relative to each other.
Claim 13
Dependent Claim
77 words
The method of claim 8 or claim 9, further comprising means for reconstructing images using the four data sets; and wherein the means for combining is adpated to combine the image data of the second and fourth data sets to form a field image which identifies the field inhomogeneity terms; and to combine the field image with the image data of the third data set to form a corrected third image which is corrected for field inhomogeneities.
Claim 14
Dependent Claim
46 words
The apparatus of claim 10, further comprising means for forming a complex sum of the image data of the first data set and the corrected third image; and for taking the magnitude of the complex sum to produce a magnitude image of one chemical shift component.
Claim 15
Dependent Claim
47 words
The method of claim 10, further comprising means for forming a complex difference of the image data of the first data set and the corrected third image; and for taking the magnitude of the complex difference to produce a magnitude image of a second chemical shift conponent.
Claim 16
Dependent Claim
65 words
Apparatus for obtaining field inhomogeneity information in an NMR environment comprising: means for obtaining a) a first data set of NMR signal information which contains virtually no field inhomogeneity information; and b) a second data set of NMR signal information which contains a characteristic set of field inhomogeneity terms; and means for combining said first and second data sets to identify said field inhomogeneity terms.
Claim 17
Dependent Claim
65 words
Apparatus for obtaining field inhomogeneity information in an NMR environment comprising: means for obtaining a) a first data set of NMR signal information which contains virtually no field inhomogeneity information; and b) a second data set of NMR signal information which contains a characteristic set of field inhomogeneity terms; and means for combining said first and second data sets to identify said field inhomogeneity terms.
Claim 18
Dependent Claim
61 words
The apparatus of claim 13, wherein said field inhomogeneity terms each include a phase angle term; and the apparatus further comprises: means for picking a phase angle of one of said terms which is within a reference range of contiguous phase angle values; and for comparing said terms to detect phase angles which are within ranges other than said reference range.
Claim 19
Dependent Claim
48 words
The apparatus of claim 14, wherein each range has a magnitude of 2π radians, and the apparatus further comprises means for compiling numerical corrections of multiples of + 2 IT for field inhomogeneity terms which contain phase angle terms which are within ranges other than said reference range.
Claim 20
Dependent Claim
134 words
Apparatus for obtaining chemical shift information in an NMR environment comprising: means for obtaining a) a first image data set of NMR signal information in which two chemical shift components are oriented relative to each other at a first angle; b) a second image data set of NM R signal information in which two chemical shift components are oriented relative to each other at a second angle, wherein said second image data set contains spatially variable field inhomogeneity terms, and c) a field map containing phase angle terms representing spatially varying field inhomogeneity; and means for combining said field map with said second image data set to produce a second image corrected for field inhomogeneities; and for combining said first image data set and said corrected second image to identify said chemical shift components.
Claim 21
Dependent Claim
134 words
Apparatus for obtaining chemical shift information in an NMR environment comprising: means for obtaining a) a first image data set of NMR signal information in which two chemical shift components are oriented relative to each other at a first angle; b) a second image data set of NM R signal information in which two chemical shift components are oriented relative to each other at a second angle, wherein said second image data set contains spatially variable field inhomogeneity terms, and c) a field map containing phase angle terms representing spatially varying field inhomogeneity; and means for combining said field map with said second image data set to produce a second image corrected for field inhomogeneities; and for combining said first image data set and said corrected second image to identify said chemical shift components.
Claim 22
Dependent Claim
97 words
The apparatus of claim 16, wherein the obtaining means is adpated to a) obtain a first image data set of NMR signal information in which two chemical shift components are oriented relative to each other at an angle of n(2T-) where n is an integer number or zero; and b) obtaining a second image data set of NMR signal information in which two chemical shift components are oriented relative to each other at an angle of m π, where m is an odd integer number, wherein said second image data set contains spatially variable field inhomogeneity terms.
Claim 23
Dependent Claim
97 words
The method of claim 16, wherein the means for obtaining is adapted to obtain a first image data set of NMR signal information in which two chemical shift components are oriented relative to each other at an angle of n(π/2), where n is a first integer number; and b) obtaining a second image data set of NMR signal information in which two chemical shift components are oriented relative to each other at an angle of m(1 f /2), where m is a second integer number, wherein said second image data set contains spatially variable field inhomogeneity terms.
Claim 24
Dependent Claim
45 words
The method of claim 16, further comprising means for forming complex sums and differences of the first image data set and the corrected second image; and for taking the magnitude of the complex sums and differences to produce magnitude images of said chemical shift components.
Claim 25
Dependent Claim
32 words
The method of claim 19, further comprising means for unwrapping said field map when the variation in field homogeneity is greater than the chemical shift separation of the two chemical shift components.
Claim 26
Dependent Claim
112 words
Apparatus for identifying chemical shift information comprising: means for generating and acquiring first and second sets of spin echo information signals at times T E relative to the time of an RF excitation pulse; means for generating and acquiring third and fourth sets of spin echo information signals at times offset from times T E and n TE by multiples of an offset time π s ; means for combining the second and fourth set of spin echo information signals to produce a data set representative of field inhomogeneity; and means for combining the field inhomogeneity data set and the third set of spin echo information signals to identify chemical shift information.
Claim 27
Dependent Claim
112 words
Apparatus for identifying chemical shift information comprising: means for generating and acquiring first and second sets of spin echo information signals at times T E relative to the time of an RF excitation pulse; means for generating and acquiring third and fourth sets of spin echo information signals at times offset from times T E and n TE by multiples of an offset time π s ; means for combining the second and fourth set of spin echo information signals to produce a data set representative of field inhomogeneity; and means for combining the field inhomogeneity data set and the third set of spin echo information signals to identify chemical shift information.
Claim 28
Dependent Claim
44 words
The apparatus of claim 21, further comprising: means for combining the third set of spin echo information signals in which the chemical shift information has been identified and the first set of spin echo information signals to separately identify components of chemical shift information.
References Cited (Backward Citations)
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