Magnetic resonance imaging method and system with adaptively selected flip angels
First Claim
1. A magnetic resonance (MR) method for imaging a moving object with reduced motion artifacts, the method comprising:
- measuring the instantaneous state of motion of the object present in an examination zone, selecting phase-encoding gradients wherein the time integrals of the selected phase-encoding gradients depend at least in part on the measured instantaneous state of motion, selecting flip angles, wherein the selected flip angles depend at least in part on the previously selected phase-encoding gradients or on the measured instantaneous state of motion, generating MR signals from the object by applying RF pulses to excite nuclear magnetization with the selected flip angles and by applying the selected phase-encoding gradients, and reconstructing an MR image from the generated MR signals.
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Abstract
This invention relates to methods and apparatus for magnetic resonance (MR) imaging of moving parts of a patient in which flip angles for the excitation of nuclear magnetization are adaptively selected during image data acquisition in order to minimize artifacts. In particular, the flip angles are selected so that a smooth distribution of signal-strengths in k-space results even though the order of phase-encoding gradients is also adaptively selected in dependence of the measured instantaneous state of motion of the moving part. The invention also includes MR apparatus for practicing the described methods and software for controlling an MR apparatus to practice the methods.
51 Citations
19 Claims
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1. A magnetic resonance (MR) method for imaging a moving object with reduced motion artifacts, the method comprising:
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measuring the instantaneous state of motion of the object present in an examination zone, selecting phase-encoding gradients wherein the time integrals of the selected phase-encoding gradients depend at least in part on the measured instantaneous state of motion, selecting flip angles, wherein the selected flip angles depend at least in part on the previously selected phase-encoding gradients or on the measured instantaneous state of motion, generating MR signals from the object by applying RF pulses to excite nuclear magnetization with the selected flip angles and by applying the selected phase-encoding gradients, and reconstructing an MR image from the generated MR signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19)
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18. A magnetic resonance (MR) apparatus for acquiring images of a moving part of a patient placed in an examination zone of the MR apparatus with reduced motion artifacts, the apparatus comprising:
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a main magnet system for generating a steady magnetic field in the examination zone, a gradient magnet system for generating temporary gradient magnetic fields in the examination zone, a radio frequency (RF) transmitter system for generating RF pulses in the examination zone, an RF receiver system for receiving MR signals from the examination zone, a reconstruction unit for reconstructing an image of the region of the patient from the received MR signals, a control unit for generating signals controlling the gradient magnet system, the RF transmitter system, the RF receiver system, and the reconstruction unit, wherein the control unit generates signals causing measurement of the instantaneous state of motion of the object present in an examination zone, selecting of phase-encoding gradients wherein the time integrals of the selected phase-encoding gradients depend at least in part on the measured instantaneous state of motion, selecting of flip angles, wherein the selected flip angles depend at least in part on the previously selected phase-encoding gradients or on the measured instantaneous state of motion, generating of MR signals from the object by applying RF pulses to excite nuclear magnetization with the selected flip angles and by applying the selected phase-encoding gradients, and reconstructing of an MR image from the generated MR signals.
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Specification