Method and apparatus for automated magnetic field shimming in magnetic resonance spectroscopic imaging

Claim 9

A multiply-tuned RF coil for use in magnetic resonance spectroscopic imaging, said coil comprising: multiple pairs of resonant Helmholtz coils, the coils in each pair being capacitively over coupled to one another; and plural adjustably positionable loading and coupling loops, one of said loops being inductively coupled to each of said Helmholtz pairs and feed-connected to a respectively associated separate RF transmission line.

Claim 10

A multiply-tuned RF coil for use in magnetic resonance spectroscopic imaging, said coil comprising: multiple pairs of resonant Helmholtz coils, the coils in each pair being capacitively over coupled to one another; and plural adjustably positionable loading and coupling loops, one of said loops being inductively coupled to each of said Helmholtz pairs and feed-connected to a respectively associated separate RF transmission line.

Claim 11

A multiply-tuned RF coil as in claim 5 further comprising: a frequency multiplexer comprising a plurality of band-pass/band-stop filters individually connected at one end to a respectively corresponding one of said transmission lines and commonly connected together at their other ends to a common RF input/output port.

Claim 14

A method as in claim 7 further comprising, after said applying step(c); (d) again performing said mapping step; (e) comparing the resulting uniformity of said B field distribution to a predetermined maximum permissible magnitude of variation; and (f) if said predetermined maximum is exceeded, repeating steps (b) and (c).

Claim 15

A method as in claim 8 wherein said predetermined maximum corresponds to 0.2 ppm or less.

Claim 16

A method as in claim 7 wherein, prior to step (a), at least one magnetic resonance image is created to define the imaging volume over which the B field distribution is to be shimmed for uniformity.

Claim 17

A method as in claim 7 which is performed while a living patient is located at least partially within said imaging volume.

Claim 18

A method as in claim 11 further comprising: thereafter taking magnetic resonance spectrographic imaging (MRSI) data on additional NMR species of nuclei without moving said patient from said imaging volume.

Claim 19

A method as in claim 12 wherein all magnetic resonance data used therein is obtained using a multiply-tuned set of RF coils coupled to the imaging volume.

Claim 20

A method as in claim 7 wherein said predetermined NMR species of nuclei comprises hydrogen nuclei.

Claim 21

A method as in claim 7 wherein all magnetic resonance data used therein is obtained from NMR spin echoes and not from FID NMR responses.

Claim 22

A method as in claim 7 further comprising generating said calibration matrix by (i) individually changing the current flowing in each of said shim coils; and (ii) measuring and recording the resulting distribution of the incremental changes in the B field per unit current.

Claim 23

A method as in claim 7 wherein step (b) is performed including a non- existent pseudo shim coil S p having an assumed uniform incremental B field distribution and calculating a corresponding pseudo-current I p which produces a uniform offset in the actual B field but with resulting improved uniformity thereover.

Claim 24

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, including means for performing calculations using an assumed uniformly distributed fictitious pseudo shim coil which does not actually exist thereby permitting uniform offset adjustments to be included in the calculations.

Claim 25

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, including means for performing calculations using an assumed uniformly distributed fictitious pseudo shim coil which does not actually exist thereby permitting uniform offset adjustments to be included in the calculations.

Claim 26

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, wherein said first means generated NMR spin echoes in an MRSI sequence which includes two degrees of phase encoding with magnetic gradient pulses and three degrees of Fourier Transformation to produce spectrographic data representing the NMR frequency of hydrogen nuclei at said locations.

Claim 27

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, wherein said first means generated NMR spin echoes in an MRSI sequence which includes two degrees of phase encoding with magnetic gradient pulses and three degrees of Fourier Transformation to produce spectrographic data representing the NMR frequency of hydrogen nuclei at said locations.

Claim 28

An improved MRSI system as in claim 18 wherein said calculation performing means generates a pseudo-current value I n+1 for a fictitious pseudo-shim coil S n+1 which is assumed to have the ability to add a uniform offset to B o within said image volume thereby causing the adjusted actual shim currents I 1 . . . I n pl to produce a more uniform actual B o within said image volume.

Claim 29

An improved MRSI system as in claim 18 further comprising: means for generating a calibration map of magnetic resonance spectrographic data representing differential shim coil contributions to B o per unit current at corresponding locations within said image volume for each of plural shim coils; and wherein said second means utilizes said calibration maps to generate the adjusted shim currents using an approximated best fit algorithm.

Claim 30

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils S 1 . . . S n to make B o intensity substantially more uniform within the image volume; and means for generating a calibration map of magnetic resonance spectrographic data representing differential shim coil contributions to B o per unit current at corresponding locations within said image volume for each of plural shim coils, wherein said second means utilizes said calibration maps to generate the adjusted shim currents using an approximated best fit algorithm, and said approximated best fit algorithm comprises at least squares fit of B o +shim coils fields to a uniform spatial distribution within said image volume using said adjusted shim currents I 1 . . . I n and said calibration maps.

Claim 31

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils S 1 . . . S n to make B o intensity substantially more uniform within the image volume; and means for generating a calibration map of magnetic resonance spectrographic data representing differential shim coil contributions to B o per unit current at corresponding locations within said image volume for each of plural shim coils, wherein said second means utilizes said calibration maps to generate the adjusted shim currents using an approximated best fit algorithm, and said approximated best fit algorithm comprises at least squares fit of B o +shim coils fields to a uniform spatial distribution within said image volume using said adjusted shim currents I 1 . . . I n and said calibration maps.

Claim 32

An improved MRSI system as in claim 21 wherein said means for generating calibration maps includes a phantom positioned within said image volume and extending substantially therebeyond in the direction of B o .

Claim 33

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils S 1 . . . S n to make B o intensity substantially more uniform within the image volume; wherein said first means generates spectrographic data for each said location which includes measured NMR response versus NMR frequency data and includes an automated peak-picker program for selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity at a corresponding location.

Claim 34

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils S 1 . . . S n to make B o intensity substantially more uniform within the image volume; wherein said first means generates spectrographic data for each said location which includes measured NMR response versus NMR frequency data and includes an automated peak-picker program for selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity at a corresponding location.

Claim 35

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils S 1 . . . S n to make B o intensity substantially more uniform within the image volume; wherein said first means uses multiple phase encoding and multiple Fourier Transformations without any applied frequency encoding magnetic gradient during the reading of NMR signal responses to produce said spectrographic data.

Claim 36

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils S 1 . . . S n to make B o intensity substantially more uniform within the image volume; wherein said first means uses multiple phase encoding and multiple Fourier Transformations without any applied frequency encoding magnetic gradient during the reading of NMR signal responses to produce said spectrographic data.

Claim 37

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, wherein said first means elicits NMR echo responses and generates said spectrographic data therefrom.

Claim 38

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, wherein said first means elicits NMR echo responses and generates said spectrographic data therefrom.

Claim 39

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, wherein said first means comprises a multiple-tuned RF coil structure including plural pairs of resonant Helmholtz coils capacitively coupled to each other and individually tuned to resonate for a respectively corresponding NMR species.

Claim 40

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; and second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume, wherein said first means comprises a multiple-tuned RF coil structure including plural pairs of resonant Helmholtz coils capacitively coupled to each other and individually tuned to resonate for a respectively corresponding NMR species.

Claim 41

An improved MRSI system as in claim 27 wherein said first means comprises: a frequency multiplexer including plural band-pass/band-stop filters connected to combine resonant NMR signals of plural frequencies from said resonant coil pairs onto a common input/output port while still isolating each resonant coil pair from other coil pair(s); and a frequency selective transmit/receive switch means connecting said common input/output port to RF signal transmitting and receiving circuits.

Claim 42

An improved MRSI system as in claim 28 wherein said transmit/receive switch means includes an RF transmission line approximately equal to an odd multiple of a quarter wavelength for RF signals emanating from plural species of NMR nuclei.

Claim 43

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume; and means for generating a locator image using phase and frequency encoded NMR signals from a predetermined single species of NMR nuclei to define the image volume to be shimmed for more uniform B o .

Claim 44

In a magnetic resonance spectrographic imaging (MRSI) system having shim coils S 1 . . . . . S n for adjusting the uniformity of a nominally static magnetic field B o within an image volume, the improvement comprising: first means for generating a map array of magnetic resonance spectrographic data representing actual B o intensity at corresponding locations within said image volume; second means for using said spectrographic data to generate and supply adjusted shim currents I 1 . . . I n to shim coils, S 1 . . . S n to make B o intensity substantially more uniform within the image volume; and means for generating a locator image using phase and frequency encoded NMR signals from a predetermined single species of NMR nuclei to define the image volume to be shimmed for more uniform B o .

Claim 45

A magnetic resonance spectroscopic imaging (MRSI) system comprising: RF coils tuned to resonate at plural frequencies f 1 and f 2 and adapted to couple RF signals at such frequencies to/from an object to be imaged; RF signal transmit and receive circuits coupled (a) to transmit RF signals at said plural frequencies to said RF coils and (b) to receive RF signals at said plural frequencies from said RF coils; a main magnet for generating a nominally static magnetic field B o throughout a predetermined image volume; plural shimming magnet coils S 1 . . . S n for controllably adjusting the uniformity of said static magnetic field B o by passing adjusted shim currents AI 1 . . . AI n through the corresponding shim coils S 1 . . . S n ; magnetic gradient coils Gx, Gy, Gz for controllably generating respective gradients in the magnetic field B o , control means connected to control sequences of RF signal transmission and reception in conjunction with magnetic gradient pulses to generate MRSI image data; said control means including shim control means which: (1) generates a map of spectrographic data representative of actual B o intensity within said image volume; (2) generates corrective shim current values AI 1 . . . AI n based on said spectrographic data for making B o intensity more uniform; and (3) adjusts the shim current values accordingly so as to make B o intensity substantially more uniform prior to generation of said MRSI image data.

Claim 46

A magnetic resonance spectroscopic imaging (MRSI) system comprising: RF coils tuned to resonate at plural frequencies f 1 and f 2 and adapted to couple RF signals at such frequencies to/from an object to be imaged; RF signal transmit and receive circuits coupled (a) to transmit RF signals at said plural frequencies to said RF coils and (b) to receive RF signals at said plural frequencies from said RF coils; a main magnet for generating a nominally static magnetic field B o throughout a predetermined image volume; plural shimming magnet coils S 1 . . . S n for controllably adjusting the uniformity of said static magnetic field B o by passing adjusted shim currents AI 1 . . . AI n through the corresponding shim coils S 1 . . . S n ; magnetic gradient coils Gx, Gy, Gz for controllably generating respective gradients in the magnetic field B o , control means connected to control sequences of RF signal transmission and reception in conjunction with magnetic gradient pulses to generate MRSI image data; said control means including shim control means which: (1) generates a map of spectrographic data representative of actual B o intensity within said image volume; (2) generates corrective shim current values AI 1 . . . AI n based on said spectrographic data for making B o intensity more uniform; and (3) adjusts the shim current values accordingly so as to make B o intensity substantially more uniform prior to generation of said MRSI image data.

Claim 47

An MRSI system as in claim 31 further comprising an RF transmitter/receiver isolation circuit including: an RF transmission line connected between the RF transmitter and receiver circuit and having an effective length which is simultaneously approximately equal to an odd multiple of quarter wavelengths for plural NMR species of nuclei, and a PIN shunt diode and associated biasing circuit for selectively short circuiting the end of said line nearest the receiver circuits.

Claim 48

An MRSI system as in claim 32 further comprising: a second RF transmission line connected serially between the first mentioned line and said receiver circuit and having an effective length less than 0.2 wavelength at all received NMR frequencies; a second PIN shunt diode for selectively short circuiting the end of said line nearest the receiver circuits.

Claim 49

Apparatus for adjusting currents in plural magnetic shim coils in an MRI/MRSI system comprising: (a) means for mapping an existing magnetic field distribution; (b) means for machine calculating an adjusted set of currents for actual shim coils to improve uniformity of field distribution while also using, in such calculation a fictitious, assumed uniformly distributed pseudo-shim coil which does not actually exist thereby permitting uniform offset adjustments to be included in the calculations; and (c) means for applying said adjusted set of currents to the actual shim coils.

Claim 50

Apparatus for adjusting currents in plural magnetic shim coils in an MRI/MRSI system comprising: (a) means for mapping an existing magnetic field distribution; (b) means for machine calculating an adjusted set of currents for actual shim coils to improve uniformity of field distribution while also using, in such calculation a fictitious, assumed uniformly distributed pseudo-shim coil which does not actually exist thereby permitting uniform offset adjustments to be included in the calculations; and (c) means for applying said adjusted set of currents to the actual shim coils.

Claim 51

Apparatus for adjusting currents in plural magnetic shim coils in an MRI/MRSI system comprising: (a) means for acquiring an MRI image of a patient volume; (b) means for defining a desired MRSI image volume therewithin; and (c) means for automatically shimming a static magnetic field within the defined MRSI image volume by mapping the existing field distribution and calculating and applying adjusted shim coil currents to improve the homogeneity of the thus mapped distribution, including means for performing calculations using an assumed uniformly distributed fictitious pseudo shim coil which does not actually exist thereby permitting uniform offset adjustments to be included in the calculations.

Claim 52

Apparatus for adjusting currents in plural magnetic shim coils in an MRI/MRSI system comprising: (a) means for acquiring an MRI image of a patient volume; (b) means for defining a desired MRSI image volume therewithin; and (c) means for automatically shimming a static magnetic field within the defined MRSI image volume by mapping the existing field distribution and calculating and applying adjusted shim coil currents to improve the homogeneity of the thus mapped distribution, including means for performing calculations using an assumed uniformly distributed fictitious pseudo shim coil which does not actually exist thereby permitting uniform offset adjustments to be included in the calculations.

Claim 53

Apparatus for automated shimming of static magnetic fields for homogeneity in an MRSI system comprising: (a) means for acquiring and using NMR spin echo responses to create NMR spectral responses from plural voxels within an image area and a map of existing magnetic field variation therewithin corresponding to the NMR spectral peak frequency of a predetermined NMR species and using same to automatically reduce said variations; and (b) means for thereafter acquiring and using NMR FID or spin echo responses to create MRSI plots of other NMR species from said image area.

Claim 54

Apparatus for automated shimming of static magnetic fields for homogeneity in an MRSI system comprising: (a) means for acquiring and using NMR spin echo responses to create NMR spectral responses from plural voxels within an image area and a map of existing magnetic field variation therewithin corresponding to the NMR spectral peak frequency of a predetermined NMR species and using same to automatically reduce said variations; and (b) means for thereafter acquiring and using NMR FID or spin echo responses to create MRSI plots of other NMR species from said image area.

Claim 55

Apparatus for automated shimming of static magnetic fields for homogeneity in an MRSI system comprising: (a) means for mapping the distribution of incremental magnetic field change per unit current to create a calibration value matrix for each of plural magnetic shim coils over a predetermined array of voxels, including means for generating spectrographic data for each voxel which includes measured NMR response versus NMR frequency data, including automated peak-picking means for selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within a corresponding voxel; (b) means for mapping and recording variations in existing static magnetic field distribution for only some of said voxels; (c) means for using said recorded variations and a subset of said calibration value matrix corresponding to only some of said voxels to calculate adjusted shim coil currents required to reduce the magnitude of said variations; and (d) means for applying said adjusted shim coil currents to respectively corresponding shim coils.

Claim 56

Apparatus for automated shimming of static magnetic fields for homogeneity in an MRSI system comprising: (a) means for mapping the distribution of incremental magnetic field change per unit current to create a calibration value matrix for each of plural magnetic shim coils over a predetermined array of voxels, including means for generating spectrographic data for each voxel which includes measured NMR response versus NMR frequency data, including automated peak-picking means for selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within a corresponding voxel; (b) means for mapping and recording variations in existing static magnetic field distribution for only some of said voxels; (c) means for using said recorded variations and a subset of said calibration value matrix corresponding to only some of said voxels to calculate adjusted shim coil currents required to reduce the magnitude of said variations; and (d) means for applying said adjusted shim coil currents to respectively corresponding shim coils.

Claim 57

Apparatus for adjusting currents in plural magnetic shim coils in a magnetic resonance imaging system, said apparatus comprising: (a) means for mapping the distribution of a static magnetic field B within an imaging volume with a first set of currents I 1 . . . I n in shim coils S 1 . . . S n by magnetic resonance spectroscopy which maps the frequency of a predetermined NMR species at an array of locations within said imaging volume, including means for generating spectrographic data for each voxel which includes measured NMR response versus NMR frequency data, including automated peak-picking means for selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within a corresponding voxel; (b) means for machine calculating an adjusted second set of shim coil currents AI 1 . . . AI n using a calibration matrix of field distributions produced by the individual shim coils and the measured existing B field distribution so as to minimize variations in the B field distribution; and (c) means for applying said adjusted shim coil currents AI 1 . . . AI n to respectively corresponding shim coils S 1 . . . S n .

Claim 58

Apparatus for adjusting currents in plural magnetic shim coils in a magnetic resonance imaging system, said apparatus comprising: (a) means for mapping the distribution of a static magnetic field B within an imaging volume with a first set of currents I 1 . . . I n in shim coils S 1 . . . S n by magnetic resonance spectroscopy which maps the frequency of a predetermined NMR species at an array of locations within said imaging volume, including means for generating spectrographic data for each voxel which includes measured NMR response versus NMR frequency data, including automated peak-picking means for selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within a corresponding voxel; (b) means for machine calculating an adjusted second set of shim coil currents AI 1 . . . AI n using a calibration matrix of field distributions produced by the individual shim coils and the measured existing B field distribution so as to minimize variations in the B field distribution; and (c) means for applying said adjusted shim coil currents AI 1 . . . AI n to respectively corresponding shim coils S 1 . . . S n .

Claim 59

Apparatus as in claim 38 further comprising, (d) means for again performing said mapping step; (e) means for comparing the resulting uniformity of said B field distribution to a predetermined maximum permissible magnitude of variation; and (f) means for repeating steps (b) and (c) if said predetermined maximum is exceeded.

Claim 60

Apparatus as in claim 38 further comprising means for creating at least one magnetic resonance image to define the imaging volume over which the B field distribution is to be shimmed for uniformity.

Claim 61

Apparatus as in claim 38 wherein: said mapping means includes means for mapping said field distribution while a patient is disposed within said imaging volume; said calculating means and said applying means each operate while said patient is disposed within said imaging volume; and said apparatus further comprises means for taking magnetic resonance spectrographic imaging (MRSI) data on additional NMR species of nuclei without moving said patient from said imaging volume after said shim currents have been adjusted.

Claim 62

Apparatus as in claim 41 wherein said means for mapping comprises a multiply-tuned set of RF coils coupled to the imaging volume.

Claim 63

Apparatus as in claim 38 wherein said means for calculating includes means for including a fictitious non-existent pseudo-shim coil S p having an assumed uniform incremental B field distribution and for calculating a corresponding pseudo-current I p which produces a uniform offset in the actual B field but with resulting improved uniformity.

Claim 64

A method as in claim 2 wherein said shimming step (c) includes the step of generating spectrographic data including measured NMR response versus NMR frequency data for each of plural voxels within said patient volume, and automatically picking peak spectrographic responses by selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within a corresponding voxel.

Claim 65

A method as in claim 4 wherein said mapping step (a) includes the steps of: (i) generating spectrographic data including measured NMR response versus NMR frequency data for each of said voxels, and (ii) automatically picking peak spectrographic responses by selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within a corresponding voxel.

Claim 66

An improved MRSI system as in claim 18 wherein said first means includes: means for generating spectrographic data including measured NMR response versus NMR frequency data for each of said voxels, and means operatively coupled to said spectrographic data generating means for automatically picking peak spectrographic responses by selecting a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within a corresponding voxel.

Claim 67

Apparatus as in claim 35 wherein said shimming means includes: means for generating spectrographic data including measured NMR response versus NMR frequency data for each of a plurality of voxels within said patient volume, and means operatively coupled to said spectrographic data generating means for automatically picking peak spectrographic response by selecting, for each of a subset of said plurality of voxels, a predetermined NMR species response peak frequency as the spectrographic data representing B o intensity within said corresponding subset of voxels.