Magnetic resonance imaging apparatus provided with means for preventing closed loop circuit formation across and between inside and outside of cryostat
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 or 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, a high frequency magnetic field generating means for generating a high frequency magnetic field to be applied to a subject and a shielded examination room which accommodates the super-conducting magnet. characterized, in that the magnetic resonance imaging apparatus further comprises means for interrupting formation of a closed loop circuit passing through the control circuit or the monitor circuit and the super-conducting coil circuit and being provided inside the shielded examination room between the superconducting magnet and the control circuit or monitor circuit.
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Accused Products
Abstract
A MRI apparatus includes a super-conducting magnet including a superconducting coil circuit having a super-conducting coil and a permanent current switch for controlling permanent current flowing through the super-conducting coil; at least one electrical circuit which is electrically connected to at least one electrical element and disposed at the outside of the super-conducting magnet; a gradient magnetic filed generating means; a high frequency magnetic field generating means; and shielded examination room which accommodates the super-conducting magnet. The apparatus further comprises means for interrupting noise current generated based on tomographic image measurement of the subject. Said means is disposed outside the super-conducting magnet and inside the shielded examination room while being inserted between the electrical circuit and the super-conducting magnet.
38 Citations
36 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 or 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, a high frequency magnetic field generating means for generating a high frequency magnetic field to be applied to a subject and a shielded examination room which accommodates the super-conducting magnet. characterized, in that the magnetic resonance imaging apparatus further comprises means for interrupting formation of a closed loop circuit passing through the control circuit or the monitor circuit and the super-conducting coil circuit and being provided inside the shielded examination room between the superconducting magnet and the control circuit or monitor circuit.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- 10. 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.
- 11. 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, 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 and a shielded examination room which accommodates the super-conducting magnet, 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 and being provided inside the shielded examination room between the superconducting magnet and the control circuit or monitor circuit.
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16. 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 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 higli frequency magnetic field generating means for generating high frequency magnetic field to be applied to a subject; and
a shielded examination room which accommodates the suner-conducting magnet, 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 and inside the shielded examination room while being inserted between the electrical circuit and the super-conducting magnet. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
- 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;
Specification