Method for recording the nuclear magnetic resonance for use in VNMR tomography

Claim 2

A nuclear-magnetic-resonance tomographic method for producing a sequence of images derived from an ensemble of nuclear spins within a preselected cross-sectional plane passing through a body, each image being associated with a particular time and representing a two-dimensional distribution of nuclear-spin polarization of the ensemble of nuclear spins in the plane, different images representing different two-dimensional distributions of nuclear-spin polarization from the same ensemble of nuclear spins as a result of different degrees of spin relaxation of the polarization at different locations within the cross-sectional plane at the diffferent times of the images, the method comprising the steps of: (a) subjecting at least a portion of the body which includes the preselected cross-sectional plane to a polarizing magnetic field to polarize the nuclear spins in the plane, the polarizing magnetic field being essentially static and effectively homogeneous in the cross-sectional plane; (b) superimposing upon said polarizing magnetic field in the cross-sectional plane at least one magnetic-resonance-tomographic-imaging magnetic gradient field produced in accordance with a magnetic-resonance-tomographic-image generation process, each magnetic gradient field having a field component directed essentially parallel to the polarizing magnetic field, the magnetic-resonance-tomographic-imaging magnetic gradient fields varying in magnitude along directions relative to the preselected cross-sectional plane effective to permit nuclear-magnetic-resonance signals to be tomographically detected from nuclear spins located in the plane in accordance with the magnetic-resonance-tomographic-image generation process; (c) exciting nuclear spins in the cross-sectional plane with a spin-echo-inducing pulse sequence of radio-frequency pulses, the pulse sequence having a first pulse and causing the excited nuclear spins to produce a sequence of spin-echo nuclear-magnetic-resonance signals in a timed relation relative to pulses in the pulse sequence, each spin-echo signal occurring at a time after the first pulse of the pulse sequence which defines a spin-echo-occurance time characteristic of the particular spin-echo signal, each spin-echo signal being representative of a distribution of nuclear-spin polarization resulting from the ensemble of nuclear spins in the cross-sectional plane under the influence of the polarizing magnetic field and the magnetic gradient fields with the nuclear spins at each different location within the plane at the degree of spin relaxation characteristic of the location at the spin-echo-occurance time of the spin-echo signal; (d) repeating steps (b) and (c) a tomographic-image-generation number of times less one, at least one magnetic-resonance-tomographic-imaging magnetic gradient field being altered with each repetition of step (b) in accordance with the magnetic-resonance-tomographic-image generation process, each repetition of steps (b) and (c) producing a sequence of spin-echo nuclear magnetic-resonance signals, each spin-echo signal in the sequence being characterized by one of the spin-echo occurance times; (e) digitizing at least a portion of each spin-echo signal; and (f) for each spin-echo occurance time, combining the digitized spin-echo signals associated with the particular spin-echo occurance time produced by the tomographic-image generation number of spin-echo-inducing pulse sequences to form a magnetic-resonance-tomographic-image in accordance with the magnetic-resonance-tomographic-image generation process, each image being characterized by the spin-echo occurance time of the digitized spin-echo signals combined to form the image and representing the two-dimensional distribution of nuclear-spin polarization resulting from the ensemble of nuclear spins in the cross-sectional plane and reflecting the different degrees of spin relaxation at different locations of the nuclear spins within the plane at the spin-echo occurance time.

Claim 3

The nuclear-magnetic-resonance-tomographic method in accordance with claim 1 wherein each sequence of spin-echo signals corresponding to a pulse sequence is digitized and stored before spin-echo signals corresponding to identical spin-echo occurance times in said sequences are combined.

Claim 4

The nuclear-magnetic-resonance-tomographic method in accordance with claim 1 wherein the spin-echo-inducing pulse sequences are selected to cause the spin-echo signals forming a sequence to vary substantially in accordance with spin-spin relaxation times of the ensemble of nuclear spins at different locations in the cross-sectional plane.

Claim 5

The nuclear-magnetic-resonance-tomographic method in accordance with claim 3 wherein each of the spin-echo-inducing pulse sequences is of a Carr-Purcell sequence type.

Claim 6

The nuclear-magnetic-resonance-tomographic method in accordance with claim 3 wherein a sufficient number of images are produced to determine e-functions characteristic of the spin-spin relaxation times of the nuclear spins at a plurality of different locations in the cross-sectional plane.

Claim 7

The nuclear-magnetic-resonance-tomographic method in accordance with claim 5 wherein for each location in the cross-sectional plane represented by the sequence of images an e-function is determined having a spin-spin relaxation time characteristic of the location.

Claim 8

The nuclear-magnetic-resonance-tomographic method in accordance with claim 5 wherein the intensity of individual locations represented in an image are corrected in accordance with e-functions determined to correspond to the locations.

Claim 9

The nuclear-magnetic-resonance-tomographic method in accordance with claim 1 wherein the spin-echo signals forming a sequence to vary substantially in accordance with the spin-lattice relaxation times of the ensemble of nuclear spins at different locations in the cross-sectional plane.

Claim 10

The nuclear-magnetic-resonance-tomographic method in accordance with claim 8 wherein each of the spin-echo-inducing pulse sequences is of a DEFT-sequence type.

Claim 11

The nuclear-magnetic-resonance-tomographic method in accordance with claim 8 wherein a sufficient number of images are produced to determine e-functions characteristic of the spin-lattice relaxaton times of the nuclear spins at a plurality of different locations in the cross-sectional plane.

Claim 12

The nuclear-magnetic-resonance-tomographic method in accordance with claim 10 wherein for each location in the cross-sectional plane represented by a sequence of images an e-function is determined having a spin-lattice relaxation time characteristic of the location.

Claim 13

The nuclear-magnetic-resonance-tomographic method in accordance with claim 10 wherein the intensity of individual locations represented in an image are corrected in accordance with e-functions determined to correspond to the locations.

Claim 14

The nuclear-magnetic-resonance-tomographic method according to claim 1 wherein the body has a thin essentially planar shape and the preselected cross-sectional plane passing through the body constitutes essentially the entire body so that nuclear-magnetic-resonance signals are tomographically detected from nuclear spins from essentially the entire body.

Claim 15

The nuclear-magnetic-resonance-tomographic method according to claim 1 wherein the body has an extended shape in a direction perpendicular to the preselected cross-sectional plane passing through the body and the step of superimposing at least one magnetic-resonance-tomographic-imaging magnetic gradient field upon the polarizing magnetic field includes imposing a slice-selection magnetic gradient field upon the polarizing field, the slice-selection magnetic gradient field having a field component directed essentially parallel to the polarizing magnetic field, said component being substantially constant in magnitude over the cross-sectional plane and varying in magnitude along a direction perpendicular to the cross-sectional plane to permit nuclear-magnetic-resonance signals to be tomographically detected from nuclear spins located in the plane in accordance with the magnetic-resonance-tomographic-image generation process.

Claim 16

A nuclear-magnetic-resonance tomographic method for producng a sequence of images derived from an ensemble of nuclear spins within a preselected cross-sectional plane passing through a body, each image being associated with a particular time and representing a two-dimensional distribution of nuclear-spin polarization of the ensemble of nuclear spins in the plane, different images representing different two-dimensional distributions of nuclear-spin polarization from the same ensemble of nuclear spins as a result of different degrees of spin relaxation of the polarization at different locations within the cross-sectional plane at the different times of the images, the method comprising the steps of: (a) subjecting at least a portion of the body which includes the preselected cross-sectional plane to a polarizing magnetic field to polarize the nuclear spins in the plane, the polarizing magnetic field being essentially static and effectively homogenous in the cross-sectional plane; (b) superimposing upon said polarizing magnetic field in the cross-sectional plane at least one magnetic-resonance-tomographic-imaging magnetic gradient field produced in accordance with a magnetic-resonance-tomographic-image generation process, each magnetic gradient field having a field component directed essentially parallel to the polarizing magnetic field, the magnetic-resonance-tomographic-imaging magnetic gradient fields varying in magnitude along directions relative to the preselected cross-sectional plane effective to permit nuclear-magnetic-resonance signals to be tomographically detected from nuclear spins located in the plane in accordance with the magnetic-resonance-tomographic-image generation process; (c) exciting nuclear spins in the cross-sectional plane with a spin-echo-inducing pulse sequence of radio-frequency pulses, the pulse sequence having a first pulse and causing the excited nuclear spins to produce a sequence of spin-echo nuclear-magnetic-resonance signals in a timed relation relative to pulses in the pulse sequence, each spin-echo signal occurring at a time after the first pulse of the pulse sequence which defines a spin-echo-occurance time characteristic of the particular spin-echo signal, each spin-echo signal being representive of a distribution of nuclear-spin polarization resulting from the ensemble of nuclear spins in the cross-sectional plane under the influence of the polarizing magnetic field and the magnetic gradient fields with the nuclear spins at each different location within the plane at the degree of spin relaxation characteristic of the location at the spin-echo-occurance time of the spin-echo signal; (d) digitizing and storing at least a portion of each spin-echo signal; (e) repeating steps (b), (c) and (d) a tomographic-image-generation number of times less one, at least one magnetic-resonance-tomographic-imaging magnetic gradient field being altered with each repetition of step (b) in accordance with the magnetic-resonance-tomographic-image generation process, each repetition of steps (b), (c) and (d) producing a stored sequence of digitized spin-echo nuclear-magnetic-resonance signals, each digitized spin-echo signal in the sequence being characterized by one of the spin-echo-occurance times; (f) after all of the spin-echo signal portions have been digitized and stored, combining for each spin-echo occurance time the digitized spin-echo signals associated with the particular spin-echo occurance time produced by the tomographic-image generation number of spin-echo-inducing pulse sequences to form a magnetic-resonance-tomographic-image in accordance with the magnetic-resonance-tomographic-image generation process, each image being characterized by the spin-echo occurance time of the digitized spin-echo signals combined to form the image and representing the two-dimensional distribution of nuclear-spin polarization resulting from the ensemble of nuclear spins in the cross-sectional plane and reflecting the different degrees of spin relaxation at different locations of the nuclear spins within the plane at the spin-echo occurance time.

Claim 17

A nuclear-magnetic-resonance tomographic method for producng a sequence of images derived from an ensemble of nuclear spins within a preselected cross-sectional plane passing through a body, each image being associated with a particular time and representing a two-dimensional distribution of nuclear-spin polarization of the ensemble of nuclear spins in the plane, different images representing different two-dimensional distributions of nuclear-spin polarization from the same ensemble of nuclear spins as a result of different degrees of spin relaxation of the polarization at different locations within the cross-sectional plane at the different times of the images, the method comprising the steps of: (a) subjecting at least a portion of the body which includes the preselected cross-sectional plane to a polarizing magnetic field to polarize the nuclear spins in the plane, the polarizing magnetic field being essentially static and effectively homogenous in the cross-sectional plane; (b) superimposing upon said polarizing magnetic field in the cross-sectional plane at least one magnetic-resonance-tomographic-imaging magnetic gradient field produced in accordance with a magnetic-resonance-tomographic-image generation process, each magnetic gradient field having a field component directed essentially parallel to the polarizing magnetic field, the magnetic-resonance-tomographic-imaging magnetic gradient fields varying in magnitude along directions relative to the preselected cross-sectional plane effective to permit nuclear-magnetic-resonance signals to be tomographically detected from nuclear spins located in the plane in accordance with the magnetic-resonance-tomographic-image generation process; (c) exciting nuclear spins in the cross-sectional plane with a spin-echo-inducing pulse sequence of radio-frequency pulses, the pulse sequence having a first pulse and causing the excited nuclear spins to produce a sequence of spin-echo nuclear-magnetic-resonance signals in a timed relation relative to pulses in the pulse sequence, each spin-echo signal occurring at a time after the first pulse of the pulse sequence which defines a spin-echo-occurance time characteristic of the particular spin-echo signal, each spin-echo signal being representive of a distribution of nuclear-spin polarization resulting from the ensemble of nuclear spins in the cross-sectional plane under the influence of the polarizing magnetic field and the magnetic gradient fields with the nuclear spins at each different location within the plane at the degree of spin relaxation characteristic of the location at the spin-echo-occurance time of the spin-echo signal; (d) digitizing and storing at least a portion of each spin-echo signal; (e) repeating steps (b), (c) and (d) a tomographic-image-generation number of times less one, at least one magnetic-resonance-tomographic-imaging magnetic gradient field being altered with each repetition of step (b) in accordance with the magnetic-resonance-tomographic-image generation process, each repetition of steps (b), (c) and (d) producing a stored sequence of digitized spin-echo nuclear-magnetic-resonance signals, each digitized spin-echo signal in the sequence being characterized by one of the spin-echo-occurance times; (f) after all of the spin-echo signal portions have been digitized and stored, combining for each spin-echo occurance time the digitized spin-echo signals associated with the particular spin-echo occurance time produced by the tomographic-image generation number of spin-echo-inducing pulse sequences to form a magnetic-resonance-tomographic-image in accordance with the magnetic-resonance-tomographic-image generation process, each image being characterized by the spin-echo occurance time of the digitized spin-echo signals combined to form the image and representing the two-dimensional distribution of nuclear-spin polarization resulting from the ensemble of nuclear spins in the cross-sectional plane and reflecting the different degrees of spin relaxation at different locations of the nuclear spins within the plane at the spin-echo occurance time.