Method and apparatus for magnetic resonance imaging

Patent metadata

Field	Value
Publication number	US-2016103196-A1
Application number	US-201514882793-A
Country	US
Kind code	A1
Filing date	Oct 14, 2015
Priority date	Oct 14, 2014
Publication date	Apr 14, 2016
Grant date	—

Abstract

To enable improved magnetic resonance imaging in the vicinity of an interference object that produces a magnetic interference field in an examination region, in a method and apparatus for magnetic resonance imaging of the examination region magnetic resonance raw data are acquired from the examination region by execution of a magnetic resonance sequence having multiple repetition intervals and refocusing of spins in the examination region at the end of each repetition interval repetition intervals. During at least part of the duration of the acquisition of the magnetic resonance raw data, a magnetic compensation gradient is activated that is opposed to the magnetic interference field.

First claim

I claim as my invention:

1 . A method for magnetic resonance imaging, comprising:
operating a magnetic resonance scanner to acquire magnetic resonance raw data from an examination region of an examination subject situated in the magnetic resonance scanner, wherein an interference object produces a magnetic interference field in the examination region; operating said magnetic resonance scanner to acquire said magnetic resonance raw data by executing a magnetic resonance data acquisition sequence comprising a plurality of repetition intervals and refocusing of nuclear spins in the examination region at an end of each repetition interval and comprising, during at least a portion of a duration of acquisition of said magnetic resonance raw data, activation of a magnetic compensation gradient that is opposed to said magnetic interference field; and compiling said magnetic resonance raw data in a memory and, via a computer, making the compiled magnetic resonance raw data available from said memory as a datafile in electronic form.

2 . A method as claimed in claim 1 comprising operating said magnetic resonance scanner in said magnetic resonance data acquisition sequence to activate said magnetic compensation gradient to compensate interference, caused by said magnetic interference field, to the refocusing of the nuclear spins in the examination region.

3 . A method as claimed in claim 1 comprising operating said magnetic resonance scanner in said magnetic resonance data acquisition sequence to activate said compensation gradient during an entirety of the duration of acquisition of said magnetic resonance raw data.

4 . A method as claimed in claim 1 comprising activating said compensation gradient during the refocusing of the nuclear spins in the examination region at each end of each of repetition interval.

5 . A method as claimed in claim 1 comprising refocusing the nuclear spins in the examination region by activating a refocusing gradient that produces a phase development of the nuclear spins in the examination region, and comprising activating said compensation gradient during said refocusing gradient in addition to said refocusing gradient.

6 . A method as claimed in claim 5 comprising activating said compensation gradient with compensation gradient parameters that are determined dependent on parameters of said refocusing gradient.

7 . A method as claimed in claim 1 comprising operating said magnetic resonance scanner with a steady-state free-precession (SSFP) magnetic resonance sequence as said magnetic resonance data acquisition sequence.

8 . A method as claimed in claim 1 comprising operating said magnetic resonance scanner with a quantitative magnetic resonance method embodying said magnetic resonance data acquisition sequence.

9 . A method as claimed in claim 8 comprising operating said magnetic resonance scanner with a magnetic resonance fingerprinting method, as said quantitative magnetic resonance method, wherein, during each repetition interval, magnetic resonance raw data for an individual magnetic resonance image are acquired and, in said processor, determining a magnetic resonance signal characteristic from each magnetic resonance image for each respective repetition interval, and making a signal comparison of said signal characteristic with a plurality of database signal characteristics stored in a database that is accessible by said processor, to identify tissue represented in each individual magnetic resonance image as a result of the comparison.

10 . A method as claimed in claim 1 comprising operating said magnetic resonance scanner, before acquiring said magnetic resonance raw data, to acquire adjustment data, and setting parameters of said magnetic compensation gradient dependent on said adjustment data.

11 . A method as claimed in claim 1 comprising operating said magnetic resonance scanner in said magnetic data acquisition sequence to emit radio-frequency excitation pulses that excite said nuclear spins with an excitation frequency, and selecting said excitation frequency to match a resonance frequency of nuclear spins in a vicinity of said interference object.

12 . A magnetic resonance apparatus comprising:
a magnetic resonance scanner; a control computer configured to operate said magnetic resonance scanner to acquire magnetic resonance raw data from an examination region of an examination subject situated in the magnetic resonance scanner, wherein an interference object produces a magnetic interference field in the examination region; said control computer being configured to operate said magnetic resonance scanner to acquire said magnetic resonance raw data by executing a magnetic resonance data acquisition sequence comprising a plurality of repetition intervals and refocusing of nuclear spins in the examination region at an end of each repetition interval and comprising, during at least a portion of a duration of acquisition of said magnetic resonance raw data, activation of a magnetic compensation gradient that is opposed to said magnetic interference field; and said control computer being configured to compile said magnetic resonance raw data in a memory and make the compiled magnetic resonance raw data available from said memory as a datafile in electronic form.

13 . A non-transitory, computer-readable data storage medium encoded with programming instructions, said storage medium being loaded into a control computer of a magnetic resonance apparatus that comprises a magnetic resonance scanner, said programming instructions causing said control computer to:
operate said magnetic resonance scanner to acquire magnetic resonance raw data from an examination region of an examination subject situated in the magnetic resonance scanner, wherein an interference object produces a magnetic interference field in the examination region; operate said magnetic resonance scanner to acquire said magnetic resonance raw data by executing a magnetic resonance data acquisition sequence comprising a plurality of repetition intervals and refocusing of nuclear spins in the examination region at an end of each repetition interval and comprising, during at least a portion of a duration of acquisition of said magnetic resonance raw data, activation of a magnetic compensation gradient that is opposed to said magnetic interference field; and compile said magnetic resonance raw data in a memory and make the compiled magnetic resonance raw data available from said memory as a datafile in electronic form.

Assignees

• Siemens Ag

Inventors

• Grodzki David

Classifications

• G01R33/0017

  Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields · CPC title

• G01R33/025

  Compensating stray fields {(G01R33/0017 takes precedence)} · CPC title

• G01R33/5659

  caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title

• G01R33/387

  Compensation of inhomogeneities · CPC title

• G01R33/56572 Primary

  caused by a distortion of a gradient magnetic field, e.g. non-linearity of a gradient magnetic field (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title