MAGNETIC RESONANCE DIFFUSION IMAGING WITH EDDY-CURRENT COMPENSATION
First Claim
1. A method for eddy current compensated diffusion imaging using magnetic resonance, the method comprising the steps of:
- a) obtaining a spin echo signal in a readout time window by excitation of a nuclear resonance signal using a first radio-frequency pulse and by refocusing that signal using at least one second radio-frequency pulse and a third radio-frequency pulse;
b) applying imaging gradient fields to spatially encode the image in slice, read and phase directions;
c) applying additional gradient fields of a specific direction and amplitude through activation of gradient pulses between each of said radio-frequency pulses and prior to said readout window, said gradient pulses having a polarity which is alternated between successive gradient pulses, a totality of said gradient pulses having a gradient time integral of zero between a time of said excitation and the center of kx or k-space, with at least two of said gradient pulses having differing gradient time integrals;
d) changing said gradient direction; and
e) repeating steps a) to c) to evenly distribute the additional gradient direction vectors over a sphere.
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Abstract
A method for eddy current compensated diffusion imaging using magnetic resonance is used to obtain a spin echo signal in a readout time window by excitation of a nuclear resonance signal using a first radio-frequency pulse and by refocusing that signal using at least one second radio-frequency pulse and a third radio-frequency pulse. Gradients fields are applied in a gradient field direction field having a strength and being activated by gradient pulses between each of said radio-frequency pulses and prior to said readout window, said gradient pulses having a polarity which is alternated between successive gradient pulses, with a totality of said gradient pulses having a gradient time integral of zero between a time of said excitation and the center of kx or k-space. At least two of said gradient pulses have differing gradient time integrals. The gradient direction is then changed and the previous steps repeated to evenly distribute gradient direction vectors over a sphere. An eddy current compensated and optimized imaging sequence is thereby produced which achieves improved imaging through optimization of signal to noise ratios of the detected signal while avoiding distortions in imaging due to magnetic fields associated with eddy currents.
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Citations
18 Claims
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1. A method for eddy current compensated diffusion imaging using magnetic resonance, the method comprising the steps of:
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a) obtaining a spin echo signal in a readout time window by excitation of a nuclear resonance signal using a first radio-frequency pulse and by refocusing that signal using at least one second radio-frequency pulse and a third radio-frequency pulse;
b) applying imaging gradient fields to spatially encode the image in slice, read and phase directions;
c) applying additional gradient fields of a specific direction and amplitude through activation of gradient pulses between each of said radio-frequency pulses and prior to said readout window, said gradient pulses having a polarity which is alternated between successive gradient pulses, a totality of said gradient pulses having a gradient time integral of zero between a time of said excitation and the center of kx or k-space, with at least two of said gradient pulses having differing gradient time integrals;
d) changing said gradient direction; and
e) repeating steps a) to c) to evenly distribute the additional gradient direction vectors over a sphere. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification