USRE37325EExpiredUtilityPatentIndex 42
Slice orientation selection arrangement
Priority: Sep 24, 1984Filed: Jan 21, 1999Granted: Aug 14, 2001
Est. expirySep 24, 2004(expired)· nominal 20-yr term from priority
G01R 33/4833
42
PatentIndex Score
0
Cited by
6
References
12
Claims
Abstract
A slice orientation selection arrangement for magnetic resonance imaging in planes oblique to the normal cartesian coordinates. The coordinates are rotated to applying gradient signals using Euler computations.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A method of imaging a subject using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI system, the method comprises the steps of:
(a) subjecting the subject to a strong static magnetic field along the Z axis in order to align magnetic spins in the Z direction in said subject being imaged;
(b) applying magnetic gradient vector pulses to vary said static field;
(c) generating FID signals by applying RF magnetic pulses rotating at Larmor frequencies to nutate said spins;
(d) selecting desired non-orthogonal imaging planes by selectively rotating the direction of the magnetic gradient vectors by determined angular amounts about coordinate axes prior to applying the magnetic gradient vector pulses;
(e) determining the angular amount to rotate the magnetic gradient vectors about the coordinate axis using visual indicators; and
(f) projecting said visual indicators onto the image of said subject being imaged.
2. A method of imaging a subject using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI system, the method comprising the steps of:
(a) subjecting the subject to a strong static magnetic field along the Z axis in order to align the magnetic spins in the Z direction in said subject being imaged;
(b) applying magnetic gradient vector pulses to vary said static field;
(c) generating FID signals by applying RF magnetic pulses rotating at Larmor frequencies to nutate said spins;
(d) selecting desired non-orthogonal planes by selectively rotating the direction of the magnetic gradient vectors by determined angular amounts about the coordinate axes prior to applying the magnetic gradient vector pulses;
(e) imaging in a first plane using the usual coordinate axes;
(f) imaging in a second plane using the usual coordinate axes;
(g) placing a visible line on the first plane in an area of interest;
(h) placing at least a visible dot in the second plane in an area of interest; and
(i) using said line and said dot to define a new plane, said new plane being the selected non-orthogonal imaging plane, wherein said newly defined plane indicates the angular amounts to rotate the direction of the magnetic gradient vector pulses.
3. A method of imaging a subject using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI system, the method comprises the steps of:
(a) subjecting the subject to a strong static magnetic field along the Z axis in order to align magnetic spins in the Z direction in the said subject being imaged;
(b) applying magnetic gradient vector pulses to vary said static field;
(c) generating FID signals by applying RF magnetic pulses rotating at a Larmor frequency to nutate said spins;
(d) selecting desired non-orthogonal imaging planes by selectively rotating the direction of the magnetic gradient vectors by determined angular amounts about the coordinate axes prior to applying the magnetic gradient vector pulses;
(e) rotating the Z gradient direction through θ degrees to Z′, the X gradient direction through θ φ degrees to X′, the Y gradient direction through ψ degrees to Y′, where θ, φ and ψ are determined angular amounts; and
(f) said last named step including multiplying the X, Y and Z gradients by a matrix A defined as follows: [ A = ( cos θcos ψ – sin θ sin φ sin ψ sin θ cos φ cos θsin ψ + sin θ sin φ cos ψ - sin θcos ψ – cos θ sin φ sin ψ cos θ cos φ - sin θsin ψ + cos θ sin φ cos ψ - sin ψ cos φ - sin φ cos φ cos ψ ) ] A = ( cos θcos ψ – sin θ sin φ sin ψ sin θ cos φ cos θsin ψ + sin θ sin φ cos ψ - sin θcos ψ – cos θ sin φ sin ψ cos θ cos φ - sin θsin ψ + cos θ sin φ cos ψ - sin ψ cos φ - sin φ cos φ cos ψ ) .
4. A method of imaging a subject using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI system, the method comprises the steps of:
(a) subjecting the subject to a strong static magnetic field along the Z axis in order to align magnetic spins in the Z direction in the said subject being imaged;
(b) applying magnetic gradient vector pulses to vary said static field;
(c) generating FID signals by applying RF magnetic pulses rotating at Larmor frequencies to nutate said spins;
(d) selecting desired non-orthogonal imaging planes by selectively rotating the direction of the magnetic gradient vectors by determined angular amounts about the coordinate axes prior to applying the magnetic gradient vector pulses; and
(e) rotating the Z, X and Y gradient direction θ degrees to Z, X, and Y respectively, wherein θ is a determined angular amount for the Z gradient, said method of rotating including multiplying the X, Y and Z gradients by a matrix B, said matrix B is defined as: B = ( cos θ sin θ 0 - sin θ cos θ 0 0 0 1 ) .
5. A method of imaging a subject using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI system, the method comprises the steps of:
(a) subjecting the subject to a strong static magnetic field along the Z axis in order to align magnetic spins in the Z direction in said subject being imaged;
(b) applying magnetic gradient vector pulses to vary said static field;
(c) generating free induction delay (FID) signals by applying RF magnetic pulses rotating at Larmor frequencies to nutate said spins;
(d) selecting desired non-orthogonal imaging planes by selectively rotating the direction of the magnetic gradient vectors by determined angular amounts about the coordinate axes prior to applying the magnetic gradient vector signals; and
(e) rotating the Z, X and Y gradients φ degrees to Z′, X′ and Y′ where φ is a determined angular amount for the X gradient by multiplying the Z, X and Y gradients by a matrix C, where C is defined as: C = ( 1 0 0 0 cos φ sin φ 0 - sin φ cos φ ) .
6. A method of imaging a subject using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI system, the method comprises the steps of:
(a) subjecting the subject to a strong static magnetic field along the Z axis in order to align magnetic spins in the Z direction in said subject being imaged;
(b) applying magnetic gradient vector pulses to vary said static fields;
(c) generating FID signals by applying RF magnetic pulses rotating at Larmor frequencies to nutate said spins;
(d) selecting desired non-orthogonal imaging planes by selectively rotating the direction of the magnetic gradient vectors by determined angular amounts about the coordinate axes prior to applying the magnetic gradient vector pulses;
(e) rotating the Z, X and Y gradient direction by ψ degrees to Z′, X′ and Y′ respectively where ψ is a determined angular amount for the Y gradient by multiplying the Z X, Y and Z gradients by a matrix D, where D is defined as: [ D = ( cos φ 0 sin ψ 0 1 0 - sin ψ 0 cos ψ ) ] D = ( cos ψ 0 sin ψ 0 1 0 - sin ψ 0 cos ψ ) .
7. A system of imaging subjects using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI systems, said system comprising:
(a) means for subjecting the subject to a strong static magnetic field along the Z axis in order to align magnetic spins in the Z direction in said subject being imaged;
(b) means for applying magnetic gradient vector pulses to vary said static field;
(c) means for generating FID signals by applying RF magnetic pulses rotated at Larmor frequencies to nutate said spins;
(d) means for selecting desired non-orthogonal imaging planes by rotating the direction of the magnetic gradient vectors by determined amounts about the coordinate axes prior to applying the magnetic gradient vector pulses; and
(e) means for determining the angular amount to rotate the magnetic gradient vectors about the coordinate axes including means for projecting visual indicators onto images of said subject being imaged.
8. A system of imaging a subject using MRI systems wherein the selected imaging plane is at any desired angle to the usual X, Y and Z coordinate axes of said MRI systems, said system comprising:
(a) means for subjecting the subject to a strong static magnetic field along the Z axis in order to align magnetic spins extending in the Z direction in said subject being imaged;
(b) means for applying magnetic gradient vector pulses to vary said static fields;
(c) means for generating free induction decay (FID) signals by applying RF magnetic pulses rotating at Larmor frequencies to nutate said spins;
(d) means for selecting desired non-orthogonal imaging planes by rotating the direction of the magnetic gradient vectors by determined angular amounts about the coordinate axis prior to applying gradient vector signals;
(e) means for rotating the Z gradient direction through θ degrees to Z′, the X gradient direction through φ degrees to X′, the Y gradient direction ψ degrees to Y′ where θ, φ and ψ are determined angular amounts;
(f) said last named means including means for multiplying the X, Y and Z gradients by a matrix A defined as follows: [ A = ( cos θ sin φ - sin θ sin φ sin ψ sin θ cos φ cos θsin ψ + sin θ sin φ sin ψ - sin θcos φ - cos θ sin φ sin ψ cos θ cos φ - sin θsin ψ + cos θ sin φ cos ψ - cos φ sin θ sin φ cos φ + cos φ ) ] A = ( cos θcos ψ - sin θ sin φ sin ψ sin θ cos φ cos θsin ψ + sin θ sin φ cos ψ - sin θcos ψ - cos θ sin φ sin ψ cos θ cos φ - sin θsin ψ + cos θ sin φ cos ψ - sin ψ cos φ - sin φ cos φ cos ψ ) .
9. The system of claim 7 including:
means for imaging in a first plane using the usual coordinate axes,
means for imaging in a second plane using the usual coordinate system;
means for placing at least a line in the first plane in an area of interest,
means for placing at least a dot in the second plane in an area of interest, and
means for using said line and said dot to define a new plane, said new plane being the selected non-orthogonal imaging plane, whereby said newly defined plane indicates the angular amounts to rotate the direction of the gradient vector signals.
10. The system of claim 7 including means for rotating the Z, X and Y gradient directions θ degrees to Z′, X′ and Y′, where θ is a determined angular amount for the Z gradient by multiplying the Z, X and Y gradients by the matrix B, where B is defined as: B = ( cos θ sin θ 0 - sin θ cos θ 0 0 0 1 ) .
11. The system of claim 7 including means for rotating the Z, X and Y gradients φ degrees to Z′, X′ and Y′ where φ is a determined angular amount for the X gradient, by multiplying the Z, X and Y gradients by the matrix C, where C is defined as: C = ( 1 0 0 0 cos φ sin φ 0 - sin φ cos φ ) .
12. The system of claim 7 including means for rotating the Y gradient direction ψ degrees to Y′, where ψ is a determined angular amount for the Y gradient by multiplying the X, Y and Z gradients by a matrix D, where D is defined as: D = ( cos ψ 0 sin ψ 0 1 0 - sin ψ 0 cos ψ ) .Cited by (0)
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