Apparatus for measuring a magnetic field

• US 20030016010A1
• Filed: 06/06/2002
• Published: 01/23/2003
• Est. Priority Date: 07/19/2001
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kandori, Akihiko, Miyashita, Tsuyoshi, Tsukamoto, Akira, Tsukada, Keiji, Suzuki, Daisuke, Yokosawa, Koichi
• Granted Patent: US 6,815,949 B2
• Time in Patent Office: Days
• US Class Current: 324/248
• CPC Class Codes: A61B 5/0522 Magnetic induction tomography
• CPC Class Codes: A61B 5/242 Detecting biomagnetic fields, e.g. magnetic fields produced by bioelectric currents
• CPC Class Codes: A61B 5/243 specially adapted for magnetocardiographic [MCG] signals
• CPC Class Codes: A61B 5/245 specially adapted for magnetoencephalographic [MEG] signals
• CPC Class Codes: G01R 33/0356 with flux feedback

Abstract

An apparatus can detect a magnetic field with a high sensitivity using an ordinary-temperature pickup coil even when the pickup coil is arranged outside a cryostat. Specifically, the apparatus for measuring a magnetic field includes a pickup coil for detecting an external magnetic field, a SQUID electrically or magnetically connected to the pickup coil, a cryostat for holding the SQUID at low temperatures, and a driving device for driving the SQUID. The pickup coil is made of a normal-conducting material and is placed at an ordinary temperature outside the cryostat. By arranging outside the cryostat, the pickup coil can be brought close to a subject and can thereby detect a weak magnetic field in the subject with a high sensitivity.

Claims

1. An apparatus for measuring a magnetic field comprising:

means for feeding a current to a living body;

a pickup coil for detecting a magnetic field induced in the living body by action of the means for feeding a current;

a superconducting quantum interference device; and

means for connecting the pickup coil to the superconducting quantum interference device,

wherein the pickup coil comprises a normal conducting member.

2. An apparatus for measuring a magnetic field, comprising:

means for feeding a current to a subject;

a pickup coil for detecting a magnetic field in the subject;

a superconducting quantum interference device;

a cryostat for holding the superconducting quantum interference device; and

means for connecting the pickup coil to the superconducting quantum interference device,

wherein the pickup coil comprises a normal conducting member and is arranged outside the cryostat.

3. The apparatus according to claim 2 further comprising control means for controlling the current fed to the subject to have a frequency of equal to or more than 1 kHz.

4. The apparatus according to claim 2 further comprising:

means for generating a current with an inverse phase with respect to the current fed to the subject; and

an inverse-phase coil to which the current with an inverse phase is applied,

wherein the inverse-phase coil is arranged at such a position that a magnetic flux can be transferred to the pickup coil.

5. The apparatus according to claim 4 further comprising current control means or controlling an amount of the current generated by the means for generating a current with an inverse phase at a desired level.

6. The apparatus according to claim 2 wherein the means for connecting the pickup coil to the superconducting quantum interference device comprises an electromagnetic interference shield member for shielding electromagnetic waves.

7. An apparatus for examination comprising:

means for applying an alternating current to an inspected subject;

a detecting probe for detecting a magnetic field generated from the inspected subject;

a superconducting quantum interference device connected to the detecting probe;

a cryostat for holding the superconducting quantum interference device; and

a detector for extracting a magnetic field with a desired frequency component from the detecting probe by using the alternating current applied to the inspected subject as a reference signal.

8. The apparatus according to claim 7 wherein the apparatus further comprises means for generating an alternating current with an inverse phase with respect to the alternating current applied to the inspected subject, and wherein the detecting probe comprises an inverse-phase coil to which the alternating current with an inverse phase is fed.

9. The apparatus according to claim 7 further comprising movement means of relative position of the detecting probe to the inspected subject.

10. The apparatus according to claim 7 wherein the detecting probe comprises:

a member made of a soft-magnetic material; and

a coil placed around the member.