Magnetic resonance examination system with field probes

Patent metadata

Field	Value
Publication number	US-10656227-B2
Application number	US-201615572202-A
Country	US
Kind code	B2
Filing date	May 9, 2016
Priority date	May 12, 2015
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A magnetic resonance examination system is disclosed comprising a field probe system to measure the magnetic field distribution of the main magnetic field and gradient magnetic field. The measurements are made in an earlier configuration and yield the resultant magnetic field due to gradient switching or external causes. From the measured resultant magnetic field the response relation is derived and stored in the memory. The response relation from the memory is available for compensating activation of the gradient fields or correction in reconstruction for the response relation in reconstruction. This compensation or correction can be carried-out in a current configuration. Thus is the current configuration to field probes are needed.

First claim

The invention claimed is:

1. A magnetic resonance examination system having an examination zone and comprising:
a main magnet to generate a stationary main magnetic field in the examination zone and
a gradient system with one or more gradient coils to generate a gradient magnetic field in the examination zone,
a reconstruction module configured to access respective sets of magnetic resonance imaging signals from the examination zone at a current configuration and at an earlier configuration
reconstruct an magnetic resonance images from the sets of magnetic resonance imaging signals acquired at the earlier and current configurations

a field probe system including
a plurality of field probes to measure a magnetic field distribution in the examination zone (i) due to a switching operation of the gradient system and/or (ii) due to a magnetic field disturbance originating externally,
a control module
to control the field probe system and configured to activate the field probe system to measure the magnetic field distribution in an earlier configuration simultaneously with the acquisition of the magnetic imaging resonance signals in the earlier configuration and
to determine a response relation representing the measured magnetic field distribution in the earlier configuration and i) due to said switching operation of the gradient system and/or (ii) due to said magnetic field disturbance originating externally,

a memory to store the response relation in association with i) said switching operation of the gradient system and/or with (ii) said magnetic field disturbance originating externally,

(a) the gradient system to apply the response relation from the memory to the gradient system so as to compensate activation the gradient coils in a current configuration and/or
(b) the reconstruction module to apply the response relation from the memory to the reconstruction module which is configured to apply corrections on the basis the response relation in the reconstruction of the magnetic resonance image from the magnetic resonance imaging signals acquired in the current configuration.

2. The magnetic resonance examination system of claim 1 , wherein the field probe system is configured to
successively measure the magnetic field distribution in various earlier configurations as a function of (i) the switching operation of the gradient system and/or (ii) the magnetic field disturbance originating externally,
determine response relations representing the measured magnetic field distributions for the various earlier configurations,
store the determined response relations in dependence of (i) said switching operations and/or (ii) said magnetic field disturbances in the memory.

3. The magnetic resonance examination system of claim 1 , wherein the field probe system is configured to determine the response relation in the form of
(a) a correlation between the measured magnetic field distribution and (i) the switching operation of the gradient system, and/or (ii) a magnetic field disturbance originating externally, or
(b) an impulse response function of the measured magnetic field distribution due to (i) said switching operation of the gradient system, and/or (ii) said magnetic field disturbance, or
(c) a step response function of the measured magnetic field distribution due to (i) said switching operation of the gradient system, and/or (ii) said magnetic field disturbance, or
(d) a modulation transfer function of the measured magnetic field distribution due to (i) said switching operation of the gradient system, and/or (ii) said magnetic field disturbance.

4. The magnetic resonance examination system of claim 1 , further comprising
one or more additional magnetic field sensors to measure external magnetic field disturbances in the current configuration, wherein
the control module is configured to activate the field probe system to retrieve from the memory the response relation that corresponds with the measured external field distribution in the current configuration.

5. The magnetic resonance examination system of claim 1 , further comprising:
one or more motion sensors to measure mechanical movements of one or more structural components of the magnetic resonance examination system, wherein
the control module of the field probe system is configured to control the field probe system to measure the magnetic field distribution in the earlier configuration of the main magnetic field and/or the gradient magnetic field due to a magnetic field disturbance originating externally in dependence of the measured mechanical movement and in the memory store the response relation associated with the measured mechanical movements in the earlier configuration and wherein
the control module of the field probe system is configured to retrieve from the memory the response relation that corresponds with the measured mechanical movement in the current configuration.

6. The magnetic resonance examination system of claim 1 , further comprising:
one or more temperature sensors to measure the temperature of a structural component, in particular the gradient coil,
wherein the control module of the field probe system is configured to activate the field probe system to measure the magnetic field distribution in the earlier configuration and store the response relation associated with the measured temperature in the earlier configuration and the control module of the field probe system is configured to from the memory retrieve the response relation that corresponds with the measured the temperature of the structural component in the current configuration.

7. A method of correction for resultant magnetic fields in an magnetic resonance examination system by a field probe system comprising:
by a plurality of field probes measure a magnetic field distribution of the main magnetic field and/or the gradient magnetic field in the examination zone (i) due to a switching operation of the gradient system and/or (ii) due to a magnetic field disturbance originating externally,
by a control module
control the field probe system and configured to activate the field probe system to measure the magnetic field distribution in the earlier configuration simultaneously with the acquisition of the magnetic imaging resonance signals in the earlier configuration and
determine a response relation representing the measured magnetic field distribution in the earlier configuration and i) due to said switching operation of the gradient system and/or (ii) due to said magnetic field disturbance originating externally

in a memory store response relation in association with the switching operation and/or the external magnetic field disturbance in the earlier configuration and
(a) the magnetic resonance examination system's gradient system to apply the response relation from the memory to the gradient system and to compensate activation the gradient coils in a current configuration on the basis of the earlier measured response field distribution and/or
(b) the magnetic resonance examination system's reconstruction module to apply response relation from the memory to the reconstruction module which is configured to apply corrections on the basis of the earlier measured response field in the reconstruction of the magnetic resonance image from the magnetic resonance imaging signals acquired in the current configuration.

8. The method of correction for resultant magnetic fields of claim 7 , wherein
successive measurements of the magnetic field distribution are made successively in various earlier configurations, simultaneously with acquiring magnetic resonance imaging signals from a patient to be examined, and as a function of (i) the switching operation of the gradient system and/or (ii) the magnet

Assignees

• Koninklijke Philips Nv

Inventors

• Gross Patrick
• Fuderer Miha

Classifications

• G01R33/389 Primary

  Field stabilisation {, e.g. by field measurements and control means or indirectly by current stabilisation} · CPC title

• G01R33/56518

  due to eddy currents, e.g. caused by switching of the gradient magnetic field · CPC title

• G01R33/56563

  caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title