Method and apparatus for magnetic resonance imaging
First Claim
1. A method for magnetic resonance imaging, wherein an imaging volume is subjected to at least one sequence of resonance frequency (RF) pulses and gradient magnetic field pulses (gradients), each RF pulse of the at least one sequence is applied in a presence of a gradient, the method comprising, in the at least one sequence:
- applying at least one first excitation RF pulse within at least one first excitation resonance-frequency range in order to excite transverse magnetization within at least one first slice location within the imaging volume and in order to form at least one first echo signal from the first slice location;
applying at least one second excitation RF pulse within at least one second excitation resonance-frequency range in order to excite transverse magnetization within at least one second slice location within the imaging volume, the at least one second slice location is distinguished from the at least one first slice location, and in order to form, prior to the at least one first echo signal, at least one second echo signal from the at least one second slice location; and
acquiring the at least one first and the at least one second echo signals in order to form a corrected data set,wherein, of the at least one first and the at least one second echo signals, at least one echo signal is formed with phase encoding, at least another echo signal is at least one reference echo signal;
at least one phase shift of the at least one reference echo signal is at least one reference phase shift, a motion-related phase shift of the at least one echo signal is compensated based on the at least one reference phase shift.
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Abstract
The method and system for correcting motion-induced phase errors in Magnetic Resonance Imaging (MRI) use a phase shift of the non-phase encoded reference echo-signal accumulated during the diffusion-weighting in order to characterize bulk motion and tissue deformation and to compensate their effect for correcting the diffusion/perfusion-weighted image. The sequences unbalanced with respect to the first motion derivative are used for distinguishing the perfusion component. The MRI apparatus provides additional excitation resonance-frequency ranges for forming the reference echo signals.
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Citations
20 Claims
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1. A method for magnetic resonance imaging, wherein an imaging volume is subjected to at least one sequence of resonance frequency (RF) pulses and gradient magnetic field pulses (gradients), each RF pulse of the at least one sequence is applied in a presence of a gradient, the method comprising, in the at least one sequence:
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applying at least one first excitation RF pulse within at least one first excitation resonance-frequency range in order to excite transverse magnetization within at least one first slice location within the imaging volume and in order to form at least one first echo signal from the first slice location; applying at least one second excitation RF pulse within at least one second excitation resonance-frequency range in order to excite transverse magnetization within at least one second slice location within the imaging volume, the at least one second slice location is distinguished from the at least one first slice location, and in order to form, prior to the at least one first echo signal, at least one second echo signal from the at least one second slice location; and acquiring the at least one first and the at least one second echo signals in order to form a corrected data set, wherein, of the at least one first and the at least one second echo signals, at least one echo signal is formed with phase encoding, at least another echo signal is at least one reference echo signal;
at least one phase shift of the at least one reference echo signal is at least one reference phase shift, a motion-related phase shift of the at least one echo signal is compensated based on the at least one reference phase shift.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for magnetic resonance imaging, wherein an imaging volume is subjected to at least one first and at least one second diffusion-weighted sequences of resonance frequency (RF) pulses and gradient magnetic field pulses (gradients), in order to form, correspondingly, a first and a second corrected data sets, the method comprising, in each of the at least one first and the at least one second diffusion-weighted sequences,
applying at least one first excitation RF pulse within at least one first excitation resonance-frequency range in a presence of a slice-selection gradient in order to excite transverse magnetization within the at least one first slice location within the imaging volume and to in order form at least one first echo signal from the at least one first slice location; -
applying, after the at least one first excitation RF pulse, at least one reference excitation RF pulse within at least one second excitation resonance-frequency range in a presence of at least one diffusion-weighted gradient in order to excite transverse magnetization within at least one second slice location within the imaging volume, the at least one second slice location is distinguished from the at least one first slice location, and in order to form, prior to the at least one first echo signal, at least one reference echo signal from the at least one second slice location; and acquiring the at least one first echo signal with phase encoding and the at least one second echo signal without phase encoding, at least one phase shift of the at least one reference echo signal, which is the at least one second echo signal, is at least one reference phase shift, the at least one reference phase shift is determined in order to compensate a motion-related phase shift of the at least one first echo signal, wherein, the second diffusion-weighted sequence is asymmetrical, which is characterized by a first derivative of the at least one reference phase shift being uncompensated, the at least one reference phase shift of the at least one first diffusion-weighted sequence is being sufficiently distinguished from the at least one reference phase shift of the at least one second diffusion-weighted sequence in order to distinguish a flow and/or perfusion component from a diffusion component of transverse magnetization decay in the first slice location based on a comparison of the first and the second corrected data sets. - View Dependent Claims (12, 13, 14)
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15. An apparatus for magnetic resonance imaging comprising:
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a resonance frequency (RF) coil means and a gradient magnetic coil means in order to subject an imaging volume to a sequence of RF pulses and gradient magnetic field pulses (gradients), each RF pulse of the sequence is applied in a presence of a gradient; a RF coil control means and a magnetic coil control means in order to apply at least one first excitation RF pulse within at least one first excitation resonance-frequency range, for exciting transverse magnetization within the at least one first slice location within the imaging volume and for forming at least one first echo signal from the at least one first slice location, and in order to apply at least one second excitation RF pulse within at least one second excitation resonance-frequency range, for exciting transverse magnetization within at least one second slice location within the imaging volume, the at least one second slice location is distinguished from the at least one first slice location, and for forming, prior to the at least one first echo signal, at least one second echo signal from the at least one second slice location; a receiver means in order to acquire the at least one first and the at least one second echo signals in order to form a corrected data set, the receiver means is adjusted to acquire, of the at least one first and the at least one second echo signals, at least one echo signal with phase encoding, wherein, at least another echo signal is at least one reference echo signal, at least one phase shift of the at least one reference echo signal is at least one reference phase shift; and a processor means in order to compensate a motion-related phase shift of the at least one echo signal based on the at least one reference phase shift. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification