Superconducting magnet device and magnetic resonance imaging system employing it
First Claim
1. A magnetic resonance imaging apparatus comprising:
- a super-conducting magnet including a super-conducting coil circuit having a super-conducting coil and a permanent current switch for controlling a permanent current flowing through the super-conducting coil and a heater element for controlling demagnetization of the super-conducting coil or a sensor element for measuring amount of liquid helium which are accommodated in a helium vessel, a control circuit or a monitor circuit which is electrically connected to the heater element and the sensor element and disposed at the outside of the helium vessel, a gradient magnetic field generating means for generating a gradient magnetic field and providing the same to a static magnetic field generated by the super-conducting magnet and a high frequency magnetic field generating means for generating a high frequency magnetic field to be applied to a subject characterized, in that the magnetic resonance imaging apparatus further comprises means for interrupting formation of a closed loop circuit across the control circuit or the monitor circuit and the super-conducting coil circuit.
2 Assignments
0 Petitions
Accused Products
Abstract
In order to provide a high intensity magnetic field open type MRI apparatus which suppresses electro-magnetic interference to super-conducting coils due to gradient magnetic field coils and high frequency magnetic field coils and to realize stable operation of super-conducting magnet, in a static magnetic field generating magnet 102, a pair of cryostats 117 are connected by a coupling tube 201 and disposed in vertical direction while sandwiching a space 118 where a subject is laid, and in vessels 202 and 203 filled with liquid helium in the respective cryostats super-conducting coils are accommodated. To the cryostats 117 an emergency demagnetizing unit 120 for attenuating magnetic field and a measurement unit 121 for monitoring helium liquid level belong, and signal cables therefor are connected to an inner circuit of the static magnetic field generating magnet 102 via a filter circuit 122. High frequency current induced when the gradient magnetic field coils and the high frequency magnetic field coils are driven is interrupted by the filter circuit 122 and is caused to flow to a connection point 123 via the outer casing of the cryostats 117, thereby, no influences are effected to the inner circuit in the cryostats 117.
16 Citations
35 Claims
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1. A magnetic resonance imaging apparatus comprising:
- a super-conducting magnet including a super-conducting coil circuit having a super-conducting coil and a permanent current switch for controlling a permanent current flowing through the super-conducting coil and a heater element for controlling demagnetization of the super-conducting coil or a sensor element for measuring amount of liquid helium which are accommodated in a helium vessel, a control circuit or a monitor circuit which is electrically connected to the heater element and the sensor element and disposed at the outside of the helium vessel, a gradient magnetic field generating means for generating a gradient magnetic field and providing the same to a static magnetic field generated by the super-conducting magnet and a high frequency magnetic field generating means for generating a high frequency magnetic field to be applied to a subject characterized, in that the magnetic resonance imaging apparatus further comprises means for interrupting formation of a closed loop circuit across the control circuit or the monitor circuit and the super-conducting coil circuit.
- View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A super-conducting magnet device comprising a super-conducting coil circuit having a super-conducting coil and a permanent current switch for controlling a permanent current flowing through the super-conducting coil and a vessel accommodating the super-conducting coil at a temperature for maintaining the same in super-conducting state characterized, in that the super-conducting magnet device further comprises means for electro-magnetically shielding the super-conducting coil from the outside of the vessel.
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9. A super-conducting magnet device comprising a super-conducting coil circuit having a super-conducting coil and a permanent current switch for controlling a permanent current flowing through the super-conducting coil and a vessel accommodating the super-conducting coil at a temperature for maintaining the same in super-conducting state characterized, in that the vessel is provided with a terminal portion for connecting a heater element or a sensor element disposed in the vessel to an external circuit and the terminal portion is provided with means for forming a closed loop circuit including the external circuit, an outer wall of the vessel and a grounding point provided at the wall.
- 10. An open type magnetic resonance imaging apparatus using a super-conducting magnet comprising a super-conducting magnet including a pair of grounded cryostats which are disposed facing in vertical direction so as to sandwich a measurement space where a subject is laid, helium vessels each being accommodated in the respective cryostats and being filled with liquid helium, a super-conducting coil circuit constituted by super-conducting coils each being disposed in the respective helium vessels and a permanent current switch which is disposed in one of the helium vessel and controls conduction of permanent current to be flown through the super-conducting coils and an element for controlling demagnetization of the respective super-conducting coils and another element for measuring amount of the liquid helium filled, a control circuit and a monitor circuit which are disposed outside the cryostats and are respectively connected electrically to the control element and the measurement element, flat plate shaped gradient magnetic field coils which are respectively disposed at facing surface sides of the respective cryostats and generate gradient magnetic field provided for static magnetic field generated by the super-conducting magnet and flat plate shaped high frequency magnetic field coils which are respectively likely disposed at facing surface sides of the respective cryostats and generate high frequency magnetic field to be applied to the subject characterized, in that the open type magnetic resonance imaging apparatus using a super-conducting magnet further comprises means for preventing high frequency current induced by the gradient magnetic field coils or the high frequency magnetic field coils from flowing in from the control circuit or the monitor circuit to the super-conducting coil circuit.
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15. A magnetic resonance imaging apparatus comprising:
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a super-conducting magnet including a super-conducting coil circuit having a super-conducting coil and a permanent current switch for controlling permanent current flowing through the super-conducting coil and a helium vessel for accommodating therein the super-conducting coil circuit and at least one electrical element;
at least one electrical circuit which is electrically connected to the electrical element and disposed at the outside of the super-conducting magnet;
a gradient magnetic field generating means for generating gradient magnetic field to be superposed over static magnetic field generated by the super-conducting magnet; and
a high frequency magnetic field generating means for generating high frequency magnetic field to be applied to a subject, characterized, in that the magnetic resonance imaging apparatus further comprises mean for interrupting noise current generated based on tomographic image measurement of the subject and of which means is disposed outside the super-conducting magnet while being inserted between the electrical circuit and the electrical element. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification