Centrally ordered phase encoding
First Claim
1. A method of magnetic resonance imaging comprising:
- (a) monitoring physical movement of at least a portion of a subject in an image region;
(b) exciting magnetic resonance of magnetic dipoles of at least a portion of the subject disposed in the image region;
(c) selecting a phase encoding gradient from a range of phase encoding gradients, which phase encoding gradient range includes a maximum phase encoding gradient, a minimum phase encoding gradient, and a multiplicity of phase encoding gradients therebetween including a central value, the phase encoding gradient is selected in accordance with the physical movement such that during first periods of physical movement the selected phase encoding gradient is closest to the central value and during second preselected periods of physical movement, the selected phase encoding gradient is distributed between the minimum and maximum phase encoding values;
(d) phase encoding magnetic field gradients in the image region with the selected phase encoding gradients;
(e) receiving resonance signals from the resonating dipoles in the image region; and
,(f) reconstructing an image representation of the portion of the subject in the image region from the resonance signals.
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Accused Products
Abstract
A portion of a subject (22) which is undergoing respiratory or other motion is disposed in an image region (20) to be examined. A respiratory or other motion monitor (50) monitors the cyclic respiratory motion and provides output signals indicative of chest expansion. A phase encoding gradient selector (60) selects the phase encoding gradient that is to be applied by a gradient magnetic field controller (40) and coil (42). A central phase encoding gradient is selected corresponding to a chest relaxation extreme and minimum and maximum phase encoding gradients are selected corresponding to a chest expansion extreme (FIG. 2). Intermediate degrees of monitored physical movement cause the selection of corresponding intermediate phase encoding gradients. Resonance signals collected during each phase encoding gradient are Fourier or otherwise transformed (80) into a corresponding view. A filter (92) weights each view such that views closest to the central phase encoding gradient are weighted most heavily and views adjacent the minimum and maximum phase encoding gradients are weighted least heavily. The physical position of pixels within each view are scaled (94) to adjust each view in accordance with the degree of physical expansion. The weighted and scaled views are transformed into an image memory (120) for display on a video display (122) or the like.
54 Citations
25 Claims
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1. A method of magnetic resonance imaging comprising:
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(a) monitoring physical movement of at least a portion of a subject in an image region; (b) exciting magnetic resonance of magnetic dipoles of at least a portion of the subject disposed in the image region; (c) selecting a phase encoding gradient from a range of phase encoding gradients, which phase encoding gradient range includes a maximum phase encoding gradient, a minimum phase encoding gradient, and a multiplicity of phase encoding gradients therebetween including a central value, the phase encoding gradient is selected in accordance with the physical movement such that during first periods of physical movement the selected phase encoding gradient is closest to the central value and during second preselected periods of physical movement, the selected phase encoding gradient is distributed between the minimum and maximum phase encoding values; (d) phase encoding magnetic field gradients in the image region with the selected phase encoding gradients; (e) receiving resonance signals from the resonating dipoles in the image region; and
,(f) reconstructing an image representation of the portion of the subject in the image region from the resonance signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of magnetic resonance imaging comprising:
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(a) monitoring physical movement of at least a portion of a subject in an image region; (b) exciting magnetic resonance of magnetic dipoles of at least a portion of the subject disposed in the image region; (c) receiving resonance signals from the resonating dipoles in the image region; (d) reordering the received resonance signals into an electronic data view for transformation into an image representation; (e) scaling the electronic data view in accordance with the monitored physical movement to shift each of the moving subject portions represented by the electronic view to represent a preselected subject position; (f) repeating steps (a) through (e) as the subject moves such that the scaling of step (e) changes with the subject movement; (g) combining a plurality of the electronic data views scaled into an image, whereby a first order correction to remove blurring from motion caused position indefiniteness is made.
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11. A method of magnetic resonance imaging comprising:
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(a) monitoring physical movement of at least a portion of a subject in an image region; (b) exciting magnetic resonance in at least a portion of the subject disposed in the image region; (c) selecting a phase encoding gradient from a range of gradients in accordance with the monitored physical movement; (d) phase encoding magnetic field gradients in the image region with the selected phase encoding gradient; (e) receiving phase encoded resonance signals from the image region; (f) converting the received resonance signals into view representations for transformation into an image representation; and
,(g) scaling each view representation in accordance with the monitored physical movement to shift the moving subject portions of the view representations to a preselected subject position, whereby a first order correction to remove blurring from motion caused position indefiniteness and a second order correction to remove motion relates ghosting are made.
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12. An apparatus for magnetic resonance imaging, the apparatus comprising:
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(a) a main magnetic field means for creating a main magnetic field through an image region; (b) a magnetic resonance excitation means for exciting magnetic resonance of magnetic dipoles in the image region; (c) a magnetic field gradient means for causing magnetic field gradients across the main magnetic field at least in the image region for at least phase encoding the magnetic resonance signals; (d) a phase encoding gradient selection means for selecting a phase encoding gradient in accordance with physical movement of a portion of a subject in the image region, the phase encoding gradient selecting means selecting a phase encoding gradient near a central value when the physical movement is adjacent one extreme movement and selecting a phase encoding gradient adjacent minimum and maximum phase encoding values when the monitored physical movement is adjacent a second extreme of movement, the phase encoding gradient selecting means being operatively connected with the magnetic field gradient means; (e) a transform means for transforming resonance signals collected with each phase encoding gradient into an intermediate view. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. An apparatus for magnetic resonance imaging, the apparatus comprising:
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(a) a main magnetic field means for creating a main magnetic field through an image region; (b) a magnetic resonance excitation means for exciting magnetic resonance of magnetic dipoles in the image region; (c) a magnetic field gradient means for causing magnetic field gradients across the main magnetic field at least in the image region for at least phase encoding the magnetic resonance signals; (d) a transform means for transforming resonance signals collected with each phase encoding gradient into an intermediate view; (e) a scaling means for selectively expanding and correcting the intermediate views along at least one axis for electronically shifting data from the moving subject portion into data representing a preselected motion state, the scaling means being operatively connected with the transforming means; and
,(f) an image memory means operatively connected with the scaling means into which the scaled intermediate views are summed.
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20. An apparatus for magnetic resonance imaging, the apparatus comprising:
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(a) a main magnetic field means for creating a main magnetic field through an image region; (b) a magnetic resonance excitation means for exciting magnetic resonance in the image region; (c) a magnetic field gradient means for causing magnetic field gradients across the main magnetic field at least in the image region for at least phase encoding the magnetic resonance signals; (d) a phase encoding gradient selection means for selecting the phase encoding gradient in accordance with monitored physical movement of a portion of a subject in the image region, the phase encoding gradient selecting means being operatively connected with the magnetic field gradient means; (e) a transform means for transforming resonance signals collected with each phase encoding gradient into an intermediate view; and
,(f) a scaling means for scaling data within each intermediate view for electronically shifting data from the moving subject portion into a preselected motion state, the scaling means being operatively connected with the transforming means. - View Dependent Claims (21)
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22. An apparatus for magnetic resonance imaging, the apparatus comprising:
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(a) a main magnetic field means for creating a main magnetic field through an image region; (b) a magnetic resonance excitation means for exciting magnetic resonance of magnetic dipoles in the image region; (c) a magnetic field gradient means for causing magnetic field gradients across the main magnetic field at least in the image region for at least phase encoding the magnetic resonance signals; (d) a phase encoding gradient selection means for selecting a phase encoding gradient in accordance with physical movement of a portion of a subject in the image region, the phase encoding gradient selection means being operatively connected with the magnetic field gradient means; (e) a transforming means for transforming resonance signals encoded with each selected phase encoding gradient into a corresponding view; (f) a filter means for weighting each view in accordance with the selected phase encoding gradient such that views with preselected phase encoding gradients are weighted more heavily than views encoded with other phase encoding gradients; and
,(g) an image memory means into which the weighted views are transformed and stored to form an image representation. - View Dependent Claims (23, 24, 25)
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Specification