US4579121A — High speed NMR imaging system

Claim 1

Independent Claim 90 words

In a method for providing an NMR image of a region using a sequence of rf excitations each involving a different field providing an array of received signals which are processed to form projection signals the steps of: exciting the region with an rf inversion pulse following the decay of the received signal; and driving the magnetization in the region back to equilibrium between rf excitations by exciting the region with an rf pulse occurring at the peak of the received spin-echo signal providing a tipping angle of substantially 90°.

Claim 2

Dependent Claim 90 words

In a method for providing an NMR image of a region using a sequence of rf excitations each involving a different field providing an array of received signals which are processed to form projection signals the steps of: exciting the region with an rf inversion pulse following the decay of the received signal; and driving the magnetization in the region back to equilibrium between rf excitations by exciting the region with an rf pulse occurring at the peak of the received spin-echo signal providing a tipping angle of substantially 90°.

Claim 3

Dependent Claim 74 words

The method as described in claim 1 where the region is a cross-section of a volume including the steps of: applying a first magnetic gradient of varying amplitude at each sequence prior to the time of receiving signals; applying a second magnetic gradient of fixed amplitude at each sequence during the time of receiving signals whereby the projections are all in the same direction; and processing the projection signals to produce a cross-sectional image.

Claim 4

Dependent Claim 86 words

In a method for providing an NMR image of a region using a sequence of rf excitations each involving a different field providing an array of received signals which are processed to form projection signals, the steps of driving the magnetization in the region back to equilibrium between rf excitations, the sequence of excitations occurring during a relaxation period of the nuclei in the region, and processing the array of projection signals so that they substantially represent the signals that would occur at a specific time.

Claim 5

Dependent Claim 86 words

In a method for providing an NMR image of a region using a sequence of rf excitations each involving a different field providing an array of received signals which are processed to form projection signals, the steps of driving the magnetization in the region back to equilibrium between rf excitations, the sequence of excitations occurring during a relaxation period of the nuclei in the region, and processing the array of projection signals so that they substantially represent the signals that would occur at a specific time.

Claim 6

Dependent Claim 60 words

The method as described in claim 3 wherein the step of driving the magnetization back to equilibrium includes the steps of: exciting the region with an rf inversion pulse following the decay of the received signal; and exciting the region with an rf pulse occurring at the peak of the received spin-echo signal providing a tipping angle of substantially 90°.

Claim 7

Dependent Claim 44 words

The method as described in claim 3 where the step of processing the signals includes the step of multiplying the projections signals by the ratio of the integral of the signals occurring substantially at the specific time to the integral of the projection signals.

Claim 8

Dependent Claim 57 words

The method as described in claim 3 where the step of processing the signals includes the step of multiplying the exponential portion of the projection signals by the ratio of the integral of the exponential portions of the projection signals occurring substantially at the specific time to the integral of the exponential portions of the projection signals.

Claim 9

Dependent Claim 53 words

The method as described in claim 3 where the sequence of excitations includes pairs of excitations each having the same gradient field with each excitation occurring substantially equally before and after the specific time and where the step of processing includes the step of adding the projection signals resulting from each excitation pair.

Claim 10

Dependent Claim 40 words

The method as described in claim 7 including the step of multiplying the added projection signals by the ratio of the integral of the projection signals occurring substantially at the specific time to the integral of the added projection signals.

Claim 11

Dependent Claim 52 words

The method as described in claim 7 including the step of multiplying the exponential portion of the added projection signals by the ratio of the integral of the exponential portion of the projection signals occurring substantially at the specific time to the integral of the exponential portion of the added projection signals.

Claim 12

Dependent Claim 32 words

The method as described in claim 3 where the step of processing includes the step of multiplying the exponential portion of the projection signals by a function of the average relaxation time.

Claim 13

Dependent Claim 120 words

In a method for producing a cross-sectional planar image of an object using nuclear magnetic resonance the steps of: exciting the magnetization of a plane of the object in the presence of a magnetic gradient normal to the plane; receiving rf signals from the nuclear spins in the plane using a first transverse gradient arrangement; processing the received rf signals to produce projection signals; exciting the plane with an rf inversion excitation to produce a spin echo signal; driving the magnetization in the plane back to equilibrium by exciting the plane with an rf pulse during the peak of the spin echo signal; repeating the sequence using different transverse gradient arrangements; and reconstructing the cross-sectional image using the projection signals.

Claim 14

Dependent Claim 120 words

In a method for producing a cross-sectional planar image of an object using nuclear magnetic resonance the steps of: exciting the magnetization of a plane of the object in the presence of a magnetic gradient normal to the plane; receiving rf signals from the nuclear spins in the plane using a first transverse gradient arrangement; processing the received rf signals to produce projection signals; exciting the plane with an rf inversion excitation to produce a spin echo signal; driving the magnetization in the plane back to equilibrium by exciting the plane with an rf pulse during the peak of the spin echo signal; repeating the sequence using different transverse gradient arrangements; and reconstructing the cross-sectional image using the projection signals.

Claim 15

Dependent Claim 68 words

The method as described in claim 11 where the steps of receiving rf signals with different transverse gradient arrangements includes the steps of: applying a first magnetic gradient of varying amplitude at each sequence prior to the time of receiving signals; and applying a second magnetic gradient of fixed amplitude at each sequence during the time of receiving signals whereby the projections are all in the same duration.

Claim 16

Dependent Claim 126 words

In a method for producing a cross-sectional planar image of an object using nuclear magnetic resonance the steps of: exciting the magnetization of a plane of the object in the presence of a magnetic gradient normal to the plane; receiving rf signals from the nuclear spins in the plane using a first transverse gradient arrangement; processing the received rf signals to produce projection signals; driving the magnetization in the plane back to equilibrium; repeating the sequence using different transverse gradient arrangements; the sequence of excitations occurring during a relaxation period of the nuclei in the plane, and processing the array of projection signals so that they substantially represent the signals that would occur at a specific time; and reconstructing the cross-sectional image using the projection signals.

Claim 17

Dependent Claim 126 words

In a method for producing a cross-sectional planar image of an object using nuclear magnetic resonance the steps of: exciting the magnetization of a plane of the object in the presence of a magnetic gradient normal to the plane; receiving rf signals from the nuclear spins in the plane using a first transverse gradient arrangement; processing the received rf signals to produce projection signals; driving the magnetization in the plane back to equilibrium; repeating the sequence using different transverse gradient arrangements; the sequence of excitations occurring during a relaxation period of the nuclei in the plane, and processing the array of projection signals so that they substantially represent the signals that would occur at a specific time; and reconstructing the cross-sectional image using the projection signals.

Claim 18

Dependent Claim 60 words

The method as described in claim 13 where the step of driving the magnetization back to equilibrium includes the steps of: inverting the nuclear spins in the plane following the decay of the received signal; and exciting the plane with an rf pulse occurring at the peak of the received spin echo signal providing a tipping angle of substantially 90°.

Claim 19

Dependent Claim 45 words

The method as described in claim 13 where the step of processing the signals includes the step of multiplying the projection signals by the ratio of the integral of the projection signals occurring substantially at the specific time to the integral of the projection signals.

Claim 20

Dependent Claim 57 words

The method as described in claim 13 where the step of processing the signals includes the step of multiplying the exponential portions of the projection signals by the ratio of the integral of the exponential portions of the projection signals occurring substantially at the specific time to the integral of the exponential portions of the projection signals.

Claim 21

Dependent Claim 54 words

The method as described in claim 13 where the sequence of excitations includes pairs of excitations each having the same transverse gradient arrangement with each excitation occurring substantially equally before and after the specific time and where the step of processing includes the step of adding the projection signals resulting from each excitation pair.

Claim 22

Dependent Claim 40 words

The method as described in claim 17 including the step of multiplying the added projection signals by the ratio of the integral of the projection signals occurring substantially at the specific time to the integral of the added projection signals.

Claim 23

Dependent Claim 52 words

The method as described in claim 17 including the step of multiplying the exponential portions of the added projection signals by the ratio of the integral of the exponential portions of the projection signals occurring substantially at the specific time to the integral of the exponential portions of the added projection signals.

Claim 24

Dependent Claim 32 words

The method as described in claim 13 where the step of processing includes the step of multiplying the exponential portion of the projection signals by a function of the average relaxation time.

Claim 25

Dependent Claim 102 words

In a method for providing three-dimensional image information about the nmr activity of an object the steps of: exciting an array of parallel planes of the object; receiving signals from the nuclear spins in each of the parallel planes using a gradient field normal to the planes; processing the received signals to produce planar integral signals; driving the magnetization in the volume to equilibrium; repeating the sequence using arrays of parallel planes at different angles with associated gradient fields normal to the planes; and reconstructing the three-dimensional image information using the planar integral signals from all of the arrays of parallel planes.

Claim 26

Dependent Claim 102 words

In a method for providing three-dimensional image information about the nmr activity of an object the steps of: exciting an array of parallel planes of the object; receiving signals from the nuclear spins in each of the parallel planes using a gradient field normal to the planes; processing the received signals to produce planar integral signals; driving the magnetization in the volume to equilibrium; repeating the sequence using arrays of parallel planes at different angles with associated gradient fields normal to the planes; and reconstructing the three-dimensional image information using the planar integral signals from all of the arrays of parallel planes.

Claim 27

Dependent Claim 139 words

In a method for providing three-dimensional image information about the nmr activity of an object the steps of exciting an array of parallel planes of the object; receiving signals from the nuclear spins in each of the parallel planes using a gradient field normal to the planes, processing the received signals to produce planar integral signals; driving the magnetization in the volume to equilibrium; repeating the sequence using arrays of parallel planes at different angles with associated gradient fields normal to the planes, the sequence of excitations occurring during a relaxation period of the nuclei in the object and processing the array of planar integral signals so that they substantially represent the signals that would occur at a specific time; and reconstructing the three-dimensional image information using the planar integral signals from all of the arrays of parallel planes.

Claim 28

Dependent Claim 139 words

In a method for providing three-dimensional image information about the nmr activity of an object the steps of exciting an array of parallel planes of the object; receiving signals from the nuclear spins in each of the parallel planes using a gradient field normal to the planes, processing the received signals to produce planar integral signals; driving the magnetization in the volume to equilibrium; repeating the sequence using arrays of parallel planes at different angles with associated gradient fields normal to the planes, the sequence of excitations occurring during a relaxation period of the nuclei in the object and processing the array of planar integral signals so that they substantially represent the signals that would occur at a specific time; and reconstructing the three-dimensional image information using the planar integral signals from all of the arrays of parallel planes.

Claim 29

Dependent Claim 58 words

The method as described in claim 22 where the step of driving the magnetization back to equilibrium includes the steps of: inverting the nuclear spins in the object following the decay of the received signal; and exciting the object with an rf pulse at the peak of the received spin-echo signal providing a tipping angle of substantially 90°.

Claim 30

Dependent Claim 54 words

The method as described in claim 22 where the sequence of excitations includes pairs of excitations each having the same gradient field with each excitation occurring substantially equally before and after the specific time and where the step of processing includes the step of adding the planar integral signals resulting from each excitation pair.

Claim 31

Dependent Claim 106 words

Apparatus for providing an image of the nmr activity in a region comprising: means for providing a sequence of rf excitations each involving a different magnetic gradient to provide an array of received signals; means for exciting the region with an rf inversion pulse following the decay of the received signal; means for driving the magnetization resulting from the rf excitations back to equilibrium between rf excitations by exciting the region with an rf pulse occurring at the peak of the received spin-echo signal providing a tipping angle of substantially 90°; and means for reconstructing the image of the region using the array of projection signals.

Claim 32

Dependent Claim 106 words

Apparatus for providing an image of the nmr activity in a region comprising: means for providing a sequence of rf excitations each involving a different magnetic gradient to provide an array of received signals; means for exciting the region with an rf inversion pulse following the decay of the received signal; means for driving the magnetization resulting from the rf excitations back to equilibrium between rf excitations by exciting the region with an rf pulse occurring at the peak of the received spin-echo signal providing a tipping angle of substantially 90°; and means for reconstructing the image of the region using the array of projection signals.

Claim 33

Dependent Claim 115 words

Apparatus for providing an image of the nmr activity in a region comprising: means for providing a sequence of rf excitations each involving a different magnetic gradient to provide an array of received signals; means for processing the received signals to form an array of projection signals; means for driving the magnetization resulting from the rf excitations back to equilibrium between rf excitations, the sequence of rf excitations occurring during a relaxation period of the nuclei in the region; means for processing the array of projection signals so that they substantially represent signals that would occur at a specific time; and means for reconstructing the image of the region using the array of projection signals.

Claim 34

Dependent Claim 115 words

Apparatus for providing an image of the nmr activity in a region comprising: means for providing a sequence of rf excitations each involving a different magnetic gradient to provide an array of received signals; means for processing the received signals to form an array of projection signals; means for driving the magnetization resulting from the rf excitations back to equilibrium between rf excitations, the sequence of rf excitations occurring during a relaxation period of the nuclei in the region; means for processing the array of projection signals so that they substantially represent signals that would occur at a specific time; and means for reconstructing the image of the region using the array of projection signals.

Claim 35

Dependent Claim 60 words

Apparatus as described in claim 26 wherein the means for driving the magnetization back to equilibrium includes: means for exciting the region with an rf inversion pulse following the decay of the received signal; and means for exciting the region with an rf pulse occurring at the peak of the received spin-echo signal providing a tipping angle of substantially 90°.

Claim 36

Dependent Claim 39 words

Apparatus as recited in claim 27 including means for applying magnetic gradients during the received spin-echo signal such that the spin-echo signal represents the same projection signal as that of the previously received signal whereby the signal is enhanced.

Claim 37

Dependent Claim 41 words

Apparatus as recited in claim 27 including means for applying different magnetic gradients during the received spin-echo signal such that the spin-echo signal represents a different projection signal whereby fewer excitations are required to form the required array of projection signals.

Claim 38

Dependent Claim 44 words

Apparatus as described in claim 26 wherein the means for processing the projection signals includes means for multiplying the projection signals by the ratio of the integral of the projection signals occurring substantially at the specific time to the integral of the projection signals.

Claim 39

Dependent Claim 56 words

Apparatus as described in claim 26 wherein the means for processing the projection signals includes means for multiplying the exponential portions of the projection signals by the ratio of the integral of the exponential portions of the projection signals occurring substantially at the specific time to the integral of the exponential portions of the projection signals.

Claim 40

Dependent Claim 33 words

Apparatus as described in claim 26 wherein the means for processing the projection signals includes means for multiplying the exponential portion of the projection signals by a function of the average relaxation time.

Claim 41

Dependent Claim 67 words

Apparatus as described in claim 26 including an additional sequence of rf excitations having the same set of magnetic gradients as those of the first sequence forming pairs of excitations having the same magnetic gradient with each of the pairs occurring substantially equally before and after the specific time and where the means for processing includes means for adding the projection signals resulting from each excitation pair.

Claim 42

Dependent Claim 38 words

Apparatus as described in claim 33 including means for multiplying the added projection signals by the ratio of the integral of the projection signals occurring substantially at the specific time to the integral of the added projection signals.

Claim 43

Dependent Claim 51 words

Apparatus as described in claim 33 including means for multiplying the exponential portion of the added projection signals by the ratio of the integral of the exponential portion of the added projection signals occurring substantially at the specific time to the integral of the exponential portion of the added projection signals.

Claim 44

Dependent Claim 24 words

Apparatus as described in claim 26 wherein the region is a planar section and the projection signals represent line integrals of the planar section.

Claim 45

Dependent Claim 43 words

Apparatus as described in claim 36 wherein the different magnetic gradients include different transverse gradient fields parallel to the planar section and each pointing in different angles and where the means for reconstructing the image includes means for reconstruction from multiple angle projections.

Claim 46

Dependent Claim 46 words

Apparatus as described in claim 36 wherein the different magnetic gradients include a transverse gradient parallel to the planar section during the time signals are received preceded by an orthogonal transverse gradient of different amplitudes and where the means for reconstructing the image includes Fourier transformation.

Claim 47

Dependent Claim 22 words

Apparatus as described in claim 26 wherein the region is a volume and the projection signals represent planar integrals of the volume.

Claim 48

Dependent Claim 29 words

Apparatus as recited in claim 26 wherein the relaxation period follows an inversion excitation whereby the received signals include functions of T 1 , the spin-lattice relaxation time constant.

Claim 49

Dependent Claim 38 words

Apparatus as recited in claim 26 wherein the relaxation period follows an excitation of substantially at 90° tipping angle followed by an inversion excitation whereby the received signals include functions of T 2 , the spin-spin relaxation time.

Claim 50

Dependent Claim 36 words

Apparatus as recited in claim 26 including means for repeating each of the rf excitations using the same magnetic gradient and means for combining the projection signals representing each magnetic gradient whereby the signal is enhanced.

Claim 51

Dependent Claim 70 words

In a method for producing an image sensitive to the NMR relaxation times of a region the steps of: acquiring a sequence of projection measurements of the region during a single relaxation period; processing the projection measurements such that they substantially represent the projection measurement that would have occurred at a specific time; and reconstructing the processed projection measurements into an image sensitive to the relaxation times of the region.

Claim 52

Dependent Claim 70 words

In a method for producing an image sensitive to the NMR relaxation times of a region the steps of: acquiring a sequence of projection measurements of the region during a single relaxation period; processing the projection measurements such that they substantially represent the projection measurement that would have occurred at a specific time; and reconstructing the processed projection measurements into an image sensitive to the relaxation times of the region.

Claim 53

Dependent Claim 42 words

The method as described in claim 43 wherein the step of processing includes the steps of multiplying each projection measurement by the ratio of the integral of the projection measurements taken at the specific time to the integral of the projection measurements.

Claim 54

Dependent Claim 32 words

The method as described in claim 43 wherein the step of processing includes the step of multiplying the exponential portion of the projection measurements by a function of the average relaxation time.

Claim 55

Dependent Claim 52 words

The method as described in claim 43 where the sequence of projection measurements includes pairs of measurements taken under substantially identical conditions with each measurement occurring substantially equally before and after the specific time and the step of processing includes the step of adding the projection measurements resulting from each measurement pair.

Claim 56

Dependent Claim 38 words

The method of claim 46 including the step of multiplying the added projection measurements by the ratio of the integral of the projection measurements occurring substantially at the specific time to the integral of the added projection measurements.

Claim 57

Dependent Claim 52 words

The method as described in claim 46 including the step of multiplying the exponential portion of the added projection measurements by the ratio of the integral of the exponential portion of the projection measurements occurring substantially at the specific time to the integral of the exponential portion of the added projection signals.

Claim 58

Dependent Claim 66 words

Apparatus for providing an image sensitive to the NMR relaxation times of a region comprising: means for acquiring a sequence of projection measurements of the region during a single relaxation period; means for processing the projection measurements such that they substantially represent the projection measurements that would have occurred at a specific time; and means for reconstructing the relaxation time-sensitive image using the processed projection measurements.

Claim 59

Dependent Claim 66 words

Apparatus for providing an image sensitive to the NMR relaxation times of a region comprising: means for acquiring a sequence of projection measurements of the region during a single relaxation period; means for processing the projection measurements such that they substantially represent the projection measurements that would have occurred at a specific time; and means for reconstructing the relaxation time-sensitive image using the processed projection measurements.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1989-03-31	1989-09-30	1990-04-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1993-03-31	1993-09-30	1994-04-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1997-03-31	1997-09-30	1998-04-01	$7700.00	Window Closed / Lapsed

High speed NMR imaging system

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