Magnetic resonance imaging apparatus and static magnetic field generating apparats used therefor

Abstract

An MRI apparatus having an open structure includes a static magnetic field generating magnet including magnetic field generating sources arranged above and below an imaging space and magnetic field fluctuation reducing plates arranged inside the magnet. Gradient magnetic field coils are fixed to the static magnetic field generating magnet so as to not be in contact with the magnetic field fluctuation reducing plates. When the strength of the magnetic field generated by the static magnetic field generating magnet fluctuates due to vibration of the gradient magnetic field coils or other devices during an imaging operation of the MRI apparatus, an eddy current is generated on the magnetic field fluctuation reducing plates in response to the magnetic field fluctuation components. Magnetic flux which cancels the static magnetic field fluctuation components is generated due to this eddy current, and consequently, a time-sequentially stable static magnetic field can be obtained.

Description

technical field [0001] The present invention relates to a magnetic resonance imaging device (hereinafter referred to as an MRI device), especially an MRI device and an MRI device with an open magnet that prevents the examinee from feeling oppressive, and improves the stability of the magnetic field in the inspection space when the device is working The static magnetic field generator used. Background technique [0002] An MRI apparatus that obtains a tomographic image of a human body using a nuclear magnetic resonance (NMR) phenomenon is widely used in the medical sector. In order to make the imaging of the MRI device correctly reflect the internal structure of the examined part of the subject, there must be a static magnetic field generating device that can generate a uniform magnetic field in the space where the subject is placed (hereinafter referred to as the examination space or imaging space). [0003] Because a uniform static magnetic field can generally be obtained ...

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Problems solved by technology

[0017] The change of the magnetic field caused by the resonance of such a superconducting coil cannot be ignored. In particular, with the increase in the use of new high-speed imaging methods such as the fast spin echo (FSE: Fast Spin Echo) method and the echo plane (Echo) method in recent years, the A large amount of energy is added to the gradient magnetic field generating device in a short time, that is, the vibration energy of the gradient magnetic field coil increases sharply, and the mechanical vibration period of the gradient magnetic field coil changes due to the expansion of the setting range of the shooting condition parameters. Changes in the magnetic field under conditions such as large can not be ignored

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