US 6,307,367 B1Granted

Magnetic resonance imaging apparatus having a device for measuring magnetic field strengths

AssigneeSiemens Aktiengesellschaft

InventorOliver Heid

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Abstract

A magnetic resonance imaging apparatus has a device for measuring magnetic field strengths including a light source that emits linearly polarized light, a Faraday cell that contains magneto-optically active material and that has at least one light outputs, the linearly polarized light emitted by the light source entering into the Faraday cell and traversing a prescribable number of optical path lengths therein and subsequently emerging via the corresponding light output. The device further has an analyzer for the linearly polarized light emerging from the Faraday cell, with the polarization plane of the analyzer being adjusted by a prescribable rotational angle relative to the polarization plane of the linearly polarized light emerging from the light source, and a light sensor that acquires the light emerging from the analyzer.

Claims28

Dependent claims

A magnetic resonance imaging apparatus comprising:

means for exciting nuclear magnetic resonance signals in a subject, said nuclear magnetic resonance signals having a magnetic field associated therewith having a field strength;
and
a device for measuring field strength comprising:
a light source which emits linearly polarized light;
a Faraday cell, exposed to said magnetic field and supplied with said linearly polarized light, containing magneto-optically active material and having at least one light output, said linearly polarized light traversing a prescribable plurality of optical path lengths in said material and emerging via said at least one light output with an intensity dependent on said field strength;
at least one analyzer supplied with said light emerging from said at least one light output of said Faraday cell, said at least one analyzer having a polarization plane which is adjustable by a prescribable rotational angle relative to a polarization plane of the linearly polarized light to admit a portion of said light emerging from said at least one light output of said Faraday cell through said analyzer;
and
at least one light sensor on which said light admitted through said at least one analyzer is incident and which emits a signal dependent on said intensity as a measure of said field strength.

5 more elements

A magnetic resonance imaging apparatus comprising:

means for exciting nuclear magnetic resonance signals in a subject and a gradient system, for generating at least one gradient magnetic field for spatially encoding said nuclear magnetic resonance signals, said gradient magnetic field having a field strength;
and
a device for measuring field strength comprising:
a light source which emits linearly polarized light;
a Faraday cell, exposed to said magnetic field and supplied with said linearly polarized light, containing magneto-optically active material and having at least one light output, said linearly polarized light traversing a prescribable plurality of optical path lengths in said material and emerging via said at least one light output with an intensity dependent on said field strength;
at least one analyzer supplied with said light emerging from said at least one light output of said Faraday cell, said at least one analyzer having a polarization plane which is adjustable by a prescribable rotational angle relative to a polarization plane of the linearly polarized light to admit a portion of said light emerging from said at least one light output of said Faraday cell through said analyzer;
and
at least one light sensor on which said light admitted through said at least one analyzer is incident and which emits a signal dependent on said intensity as a measure of said field strength.

5 more elements

Dependencies are inferred from the claim text.