Magnetic attraction preventive system

1. A magnetic attraction preventive system comprising:

an approach detection unit which generates an approach detection magnetic field and detects the approach of a magnetic material to a magnetic resonance imaging apparatus on the basis of a variation in the strength of the approach detection magnetic field;

a preventive unit which prevents magnetic attraction of the magnetic material to the magnetic resonance imaging apparatus when the approach detection unit detects the approach of the magnetic material to the magnetic resonance imaging apparatus; and

a cancellation magnetic field generation unit which generates a cancellation magnetic field to cancel out leakage magnetic fields which are generated by the magnetic resonance imaging apparatus and extends to an area where the approach detection unit detects the approach detection magnetic field.

2. The magnetic attraction preventive system according to claim 1 , wherein the preventive unit is adapted to prevent magnetic attraction of the magnetic material to the magnetic resonance imaging apparatus by at least one of the operations of making a warning, interposing an obstacle between the magnetic resonance imaging apparatus and the magnetic material, and extinguishing magnetic fields generated by the magnetic resonance imaging apparatus.

3. The magnetic attraction preventive system according to claim 2 , wherein the warning is made through at least one of the operations of producing a warning sound, producing a warning light, and displaying a warning message.

4. The magnetic attraction preventive system according to claim 1 , wherein the preventive unit continues the operation of preventing magnetic attraction of the magnetic material to the magnetic resonance imaging apparatus until the approach of the magnetic material to the magnetic resonance imaging apparatus becomes undetected by the approach detection unit.

5. A magnetic attraction preventive system an approach detection unit which generates an approach detection magnetic field and detects the approach of magnetic material to a magnetic resonance imaging apparatus on the basis of a variation in the strength of the approach detection magnetic field;

a preventive unit which prevents magnetic attraction of the magnetic material to the magnetic resonance imaging apparatus when the approach detection unit detects the approach of the magnetic material to the magnetic resonance imaging apparatus; and

wherein the approach detection unit includes at least one detection module which includes a detection magnetic field generating unit which generates the approach detection magnetic field, a magnetic field strength detection unit which detects the strength of the approach detection magnetic field generated by the detection magnetic field generating unit, and a judgment unit which judges whether or not the magnetic material has approached the magnetic resonance imaging apparatus on the basis of a variation in the strength of the approach detection magnetic field detected by the magnetic field detection unit.

6. The magnetic attraction preventive system according to claim 5 , wherein the detection magnetic field generating unit includes a coil, and a supply unit which supplies the coil with a control current to cause the coil to generate the approach detection magnetic field.

7. The magnetic attraction preventive system according to claim 6 , wherein the control current is a direct current.

8. The magnetic attraction preventive system according to claim 6 , wherein the control current is an alternating current.

9. The magnetic attraction preventive system according to claim 5 , wherein the detection module detects the approach of a magnetic material to the magnetic resonance imaging apparatus through a first entrance set between an examination room in which the magnetic resonance imaging apparatus is installed and a front room next to the examination room.

10. The magnetic attraction preventive system according to claim 9 , further comprising a controller which controls the detection module to initiate a detection operation in response to an operation of a door set at a second entrance of the front room.

11. The magnetic attraction preventive system according to claim 5 , wherein said at least one detection module includes two detection modules, one of the two detection modules detecting the approach of a magnetic material to the magnetic resonance imaging apparatus through a first entrance set between an examination room in which the magnetic resonance imaging apparatus is installed and a front room next to the examination room, and another one of the two detection modules detecting the approach of the magnetic material to the magnetic resonance imaging apparatus through a second entrance of the front room.

12. The magnetic attraction preventive system according to claim 5 , wherein the detection magnetic field generating unit has a function of changing the strength of the approach detection magnetic field in a test mode, and

further comprises a failure detection unit which detects a failure in the detection module on the basis of a variation in the strength of the magnetic field detected by the magnetic field detection unit in the test mode.

13. The magnetic attraction preventive system according to claim 12 , further comprising a transmission unit which sends information indicating the results of detection by the failure detection unit to a remote service center or the magnetic resonance imaging apparatus.

14. A magnetic attraction preventive system comprising:

an approach detection unit which detects the approach of a magnetic material to a magnetic resonance imaging apparatus;

a preventive unit which prevents magnetic attraction of the magnetic material to the magnetic resonance imaging apparatus when the approach detection unit detects the approach of the magnetic material to the magnetic resonance imaging apparatus; and

a cancellation magnetic field generation unit which generates a cancellation magnetic field to cancel out leakage magnetic fields from the magnetic resonance imaging apparatus.

15. A magnetic attraction preventive system comprising:

an approach detection unit which detects the approach of a magnetic material to a magnetic resonance imaging apparatus;

a preventive unit which prevents magnetic attraction of the magnetic material to the magnetic resonance imaging apparatus when the approach detection unit detects the approach of the magnetic material to the magnetic resonance imaging apparatus; and

a judgment unit which judges the presence or absence of a failure in the approach detection unit on the basis of an output of the approach detection unit.