Abstract: In MRI using an SE-based pulse sequence, an object is to suppress flow artifacts and acquire a flow artifact-free image regardless a velocity or a direction of blood flow. A pair of gradient magnetic field pulses are applied before and after a 180-degree pulse of the SE-based pulse sequence, and a plurality of times of imaging are performed using varying intensities of the pair of gradient magnetic field pulses. Image reconstruction is performed by performing a Fourier transformation on measurement data obtained through the plurality of times of imaging in an axial direction of the intensities of the gradient magnetic field pulses, that is, a velocity encoding direction. As a result, images can be separated for each velocity of a stationary tissue and a non-stationary component included in tissues, and an image of spins with a velocity of zero, that is, a flow artifact-free image of the stationary tissue, can be obtained.

Abstract: Preventing blood flow artifacts from being increased in an imaging plane allows reduction of the blood flow artifacts in the cross section subsequently excited. In the imaging using a spin-echo (SE) pulse sequence, an excitation width of a 90° pulse is extended from an imaging plane to one side. This one side indicates a downstream side of the blood flow with respect to a vessel of interest. In imaging multiple slices, the order of measuring the multiple imaging slices is set along the direction in which the width is extended.

Abstract: Generation of artifacts caused by the FID signal is suppressed even when the parallel imaging is applied to the imaging using a spin echo type pulse sequence. In performing a pulse sequence of a spin echo type using an excitation RF pulse for exciting nuclear spin and an inversion RF pulse for inverting excited nuclear spin as a high-frequency magnetic field pulse, a high-frequency transmitter of a MRI apparatus changes the phase of the inversion RF pulse according to the phase encoding and the phase encoding number imparted for each echo signal. Specifically, the phase of the inversion RF pulse is controlled to be a quadratic function of the phase encode of the echo signal.

Abstract: Generation of artifacts caused by the FID signal is suppressed even when the parallel imaging is applied to the imaging using a spin echo type pulse sequence. In performing a pulse sequence of a spin echo type using an excitation RF pulse for exciting nuclear spin and an inversion RF pulse for inverting excited nuclear spin as a high-frequency magnetic field pulse, a high-frequency transmitter of a MRI apparatus changes the phase of the inversion RF pulse according to the phase encoding and the phase encoding number imparted for each echo signal. Specifically, the phase of the inversion RF pulse is controlled to be a quadratic function of the phase encode of the echo signal.

Abstract: A navigator echo is acquired during imaging, and when frequency is corrected based on phase change, the correction is performed with high accuracy without being affected by an offset caused by variations with time. An MRI apparatus including a navigation controller is configured to control an imaging unit acquiring an NMR signal, generate the navigator echo and collect navigation data during a predetermined measurement time, prior to collection of nuclear magnetic resonance signals for reconstructing an image of a subject. The phase change of the navigator echo is analyzed during the measurement time to calculate a correction value for correcting misalignment due to the phase change with a navigation analyzer that calculates a phase change amount relative to a reference, based on a difference between the phase change of the navigator echo and the phase change of the navigator echo serving as the reference during the measurement time.

Abstract: A navigator echo is acquired during imaging, and when frequency is corrected based on phase change, the correction is performed with high accuracy without being affected by an offset caused by variations with time. An MRI apparatus including a navigation controller is configured to control an imaging unit acquiring an NMR signal, generate the navigator echo and collect navigation data during a predetermined measurement time, prior to collection of nuclear magnetic resonance signals for reconstructing an image of a subject. The phase change of the navigator echo is analyzed during the measurement time to calculate a correction value for correcting misalignment due to the phase change with a navigation analyzer that calculates a phase change amount relative to a reference, based on a difference between the phase change of the navigator echo and the phase change of the navigator echo serving as the reference during the measurement time.

Abstract: A magnetic resonance imaging device produces a magnetic field gradient with parallel driving of positive-side subcoils and negative-side subcoils with different power sources in the magnetic field gradient direction, to detect a misalignment in drive timing of the positive side and the negative side. Pulse sequences for timing misalignment detection having a slice magnetic field gradient pulse and a read-out magnetic field gradient pulse in the same direction as a magnetic field gradient of interest are executed. A positive-side slice echo and a negative-side slice echo of the magnetic field gradient are acquired. A phase difference between a positive-side projection image and a negative-side projection image is derived by computation with phase error from other factors being removed. From the slope of the phase difference with respect to a location, the drive timing misalignment between the positive-side subcoil and the negative-side subcoil of the magnetic field gradient production is detected.

Abstract: To supply a magnetic resonance imaging (MRI) apparatus capable of shifting a high frequency of noise into a low frequency during measurement, the magnetic resonance imaging apparatus includes: a gradient magnetic field device (9, 10) that applies a pulse-shaped gradient magnetic field to an object placed in a static magnetic field; and a measurement control unit (4) that drives the gradient magnetic field device by a gradient magnetic field pulse and measures magnetic resonance image data. The measurement control unit performs noise suppression control to shift a frequency of noise generated by the gradient magnetic field device to a low frequency side by changing a waveform of the gradient magnetic field pulse during repetition of the gradient magnetic field pulses at a constant period.

Abstract: In an MRI apparatus, RF shimming is performed with high precision in a short time irrespective of an object and an imaging mode. A database storing the shim parameter according to a change from a criterion state in advance is included when a state in which an shim parameter is calculated is set as the criterion state of the objet in order to obtain a high-quality image. At the time of imaging, the shim parameter registered in the database in association with a change amount closest to a change amount from the criterion state is used. In the database, the shim parameter calculated from a previously measured result is registered.

Abstract: To supply a magnetic resonance imaging (MRI) apparatus capable of shifting a high frequency of noise into a low frequency during measurement, the magnetic resonance imaging apparatus includes: a gradient magnetic field device (9, 10) that applies a pulse-shaped gradient magnetic field to an object placed in a static magnetic field; and a measurement control unit (4) that drives the gradient magnetic field device by a gradient magnetic field pulse and measures magnetic resonance image data. The measurement control unit performs noise suppression control to shift a frequency of noise generated by the gradient magnetic field device to a low frequency side by changing a waveform of the gradient magnetic field pulse during repetition of the gradient magnetic field pulses at a constant period.

Abstract: A magnetic resonance imaging device produces a magnetic field gradient with parallel driving of positive-side subcoils and negative-side subcoils with different power sources in the magnetic field gradient direction, to detect a misalignment in drive timing of the positive side and the negative side. Pulse sequences for timing misalignment detection having a slice magnetic field gradient pulse and a read-out magnetic field gradient pulse in the same direction as a magnetic field gradient of interest are executed. A positive-side slice echo and a negative-side slice echo of the magnetic field gradient are acquired. A phase difference between a positive-side projection image and a negative-side projection image is derived by computation with phase error from other factors being removed. From the slope of the phase difference with respect to a location, the drive timing misalignment between the positive-side subcoil and the negative-side subcoil of the magnetic field gradient production is detected.