Three-dimensional spiral echo volume imaging
First Claim
1. In an echo volume magnetic resonance imaging method in which selected dipoles in a volume of interest are induced to resonate by an RF pulse and in which a series of gradients are applied after the RF pulse and in the absence of any additional RF pulses such that resonance signal data is simultaneously detected and spatially encoded along a preselected data collection trajectory in three dimensions in k-space, the improvement comprising:
- applying the magnetic field gradients such that the trajectory in k-space follows a three-dimensionally curving spiral trajectory through the three-dimensions.
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Abstract
Magnetic resonance imaging data of a volume of interest is collected by applying a radio frequency pulse (70, 96) and following the pulse with gradients applied along three axes (x,y,z). The gradients along x and y-axes are generally sinusoidal, which sinusoids increase and decrease in magnitude to define beat patterns of a common period. The period of the first and second gradients is an integer multiple of the gradient along the z-axis. In the embodiment of FIGS. 2A and 2B, the beats of the first and second gradients increase linearly and the third gradient oscillates in a linearly expanding generally sinusoidal pattern such that k-space is traversed by a trajectory that spirals around a series of spheres (50, 52, 54, 56, 58, 60) of progressively smaller radius. Blips or spikes (78) are preferably applied between each half cycle of the third gradient to step the trajectory to the radius of the next concentric sphere. In the embodiment of FIGS. 3A and 3B, the magnitude of the beats of the first and second gradients remain substantially constant and the gradient pulses along the third axis are applied generally between and at the mid-point of each beat such that the trajectory through k-space follows a series of parallel spirals lying along a cylinder. In the embodiment of FIGS. 4-4D, the beat patterns again increase linearly and the third gradient alternates polarity with each half beat such that the trajectory through k-space spirals around a series of concentric cones.
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Citations
19 Claims
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1. In an echo volume magnetic resonance imaging method in which selected dipoles in a volume of interest are induced to resonate by an RF pulse and in which a series of gradients are applied after the RF pulse and in the absence of any additional RF pulses such that resonance signal data is simultaneously detected and spatially encoded along a preselected data collection trajectory in three dimensions in k-space, the improvement comprising:
applying the magnetic field gradients such that the trajectory in k-space follows a three-dimensionally curving spiral trajectory through the three-dimensions. - View Dependent Claims (2, 6, 7)
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3. In an echo volume imaging method in which selected dipoles in an entire volume of interest are induced to resonate by at least one RF pulse and in which a series of gradients are applied concurrently in the absence of RF pulses such that views of data are collected along a preselected data collection trajectory in three dimensions in k-space, the improvement comprising:
configuring the magnetic field gradients such that the trajectory in k-space follows spiraling paths which lie along a series of spheroidal surfaces of a multiplicity of radii. - View Dependent Claims (4, 5)
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8. A method of echo volume magnetic resonance imaging comprising:
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applying a radio frequency pulse to excite magnetic resonance in a volume of interest as a whole; after exciting magnetic resonance in the whole volume, simultaneously sampling and spatially encoding the excited magnetic resonance in the absence of radio frequency pulses along a curving three-dimensional trajectory through k-space, including concurrently; applying a first magnetic field gradient along a first axis, the first magnetic field gradient being generally sinusoidal and increasing and decreasing in magnitude in a beat pattern with a first period; applying a second magnetic field gradient along a second axis, the second magnetic field gradient being generally sinusoidal and increasing and decreasing in magnitude in a beat pattern with the first period; applying a third magnetic field gradient along a third axis, the third gradient having a second period, one of the first and second periods being an integer multiple of the other; sampling magnetic resonance data at least during each half cycle of one of the first and second sinusoidal gradients; reconstructing the sampled data into a volumetric magnetic resonance image representation. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 18, 19)
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17. A method of echo volume imaging comprising:
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applying a radio frequency pulse to excite magnetic resonance in a whole volume of interest; in the absence of additional radio frequency pulses and before the excited resonance decays away, concurrently; applying a first magnetic field gradient along a first axis, the first magnetic field gradient being generally sinusoidal and rapidly increasing and decreasing in magnitude in a beat pattern with a first periodicity; applying a second magnetic field gradient along a second axis, the second magnetic field gradient being generally sinusoidal and increasing and decreasing in magnitude in a beat pattern with the first periodicity, the beats of the first and second gradients increasing or decreasing peak amplitudes, such that k-space is traversed along conical spirals; applying a third magnetic field gradient along a third axis the third gradient having a second periodicity, one of the first and second periodicities being an integer multiple of the other, the third gradient alternating polarity adjacent the beginning and mid-point of each beat; sampling the magnetic resonance such that the magnetic resonance is sampled along a spirally conical trajectory in k-space; reconstructing the sampled data into a volumetric image representation.
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Specification