Patent ID: 6853185
Filing Date: 2005-02-08
Classification: G01R

Abstract:
1. A magnetic field measurement system comprising: a magnetically shielding device having a cylindrical magnetic shield composed of a ferromagnetic material; a plurality of sensing magnetometers having respective SQUIDs and respective pickup coils and arranged in two dimensions to sense a magnetic field component of a magnetic field emitted from a living body which is perpendicular to a center axis of said cylindrical magnetic shield; a first reference magnetometer having a SQUID and a pickup coil to sense a magnetic field component of an external field which is parallel to said center axis; a dewar for accommodating and cooling said plurality of sensing magnetometers and said first reference magnetometer, in which said plurality of sensing magnetometers are arranged in two dimensions on a first plane close to said center axis such that a plane of said pickup coils of said plurality of sensing magnetometers is parallel to said center axis and said reference magnetometer is positioned on a second plane perpendicular to said first plane in spaced apart relation to said first plane such that a plane of said pickup coil of said first reference magnetometer is perpendicular to said first plane; a gantry for holding said dewar internally of said cylindrical magnetic shield; a measurement circuit for driving said plurality of sensing magnetometers and said first reference magnetometer to sense said perpendicular magnetic field component and said parallel magnetic field component and outputting the sensed magnetic field components as measurement signals and a first reference signal; a device for recording said measurement signals; and an analyzing device for analyzing said measurement signals and displaying a result of analysis, wherein said analyzing device performs an arithmetic operation of subtracting a value obtained by multiplying said first reference signal sensed by said first reference magnetometer by a first specified factor from a difference between said measurement signals sensed by two of said sensing magneto-meters disposed at different positions to determine a first corrected measurement signal under less influence of said external field.