Magnetic resonance imaging method and apparatus

Patent metadata

Field	Value
Publication number	US-2016116557-A1
Application number	US-201514921321-A
Country	US
Kind code	A1
Filing date	Oct 23, 2015
Priority date	Oct 23, 2014
Publication date	Apr 28, 2016
Grant date	—

Abstract

A magnetic resonance image is generated by executing a scan sequence that is determined by at least one scan parameter. A first value of the at least one scan parameter is determined for a first subregion of an examination region, and a second value of the at least one scan parameter is determined for a second subregion of the examination region. The determination of the first value and the determination of the second value is implemented so that a value of a physical variable influenced by the first value and the second value of the at least one scan parameter does not transgress a pre-set threshold value. Subsequently, the scan sequence is executed by a magnetic resonance scanner and a magnetic resonance image is generated. The threshold value can be based, for example, on technical efficiency of the scanner and/or a physiological limitation of an examination object.

First claim

I claim as my invention:

1 . A method for generating a magnetic resonance (MR) image, comprising:
using a processor to designate a scan sequence for operating an MR scanner to obtain acquired MR data from an examination region of an examination object while the examination object is situated in the MR scanner, said scan sequence comprising at least on scan parameter; in said processor, automatically determining a first value of said at least one scan parameter for a first subregion of the examination region, and determining a second value of said at least one scan parameter for a second subregion of the examination region; in said processor, determining each of said first value and said second value so as to cause a value of a physical variable, that is influenced by the first value and the second value of the at least one scan parameter, to adhere to a predetermined threshold value; using said processor to operate said MR scanner with said scan sequence with said first value of said at least one scan parameter in said first subregion and with said second value of said at least one scan parameter in said second subregion, to obtain said acquired MR data for the examination region; and in said processor, reconstructing an MR image of the examination region from the acquired MR data, and making the reconstructed MR image available in electronic form as a data file from said processor.

2 . A method as claimed in claim 1 wherein said first value of said at least one scan parameter causes a reduced quality of said MR image in said first subregion, with respect to a quality of the MR image in said second subregion caused by said second value of said at least one scan parameter.

3 . A method as claimed in claim 1 comprising determining said first value of said at least one scan parameter dependent on a proportion of MR signal-generating material in said first subregion.

4 . A method as claimed in claim 1 comprising determining said first value and said second value of said at least one scan parameter by:
obtaining a candidate value of said at least one scan parameter;
determining a value of the physical variable dependent on said candidate value;
making a threshold value comparison between the determined value of the physical variable and the predetermined threshold value, thereby obtaining a comparison result; and
dependent on said comparison result, selectively adjusting said candidate value in said first subregion to obtain said first value of said at least one scan parameter, and using said candidate value in said second subregion as said second value of said at least one scan parameter.

5 . A method as claimed in claim 1 comprising determining each of said first subregion and said second subregion from at least one source selected from the group consisting of an anatomical landmark in reference image data of the examination region, and a user entry via a user interface of said processor.

6 . A method as claimed in claim 5 comprising:
determining said first subregion and said second subregion so that said second subregion contains a structure of the examination object, desired to be shown in said MR image; and
determining said first subregion and said second subregion so that said first subregion contains a surrounding environment of said structure.

7 . A method as claimed in claim 1 comprising determining said first value of said at least one scan parameter spatially resolved within said first subregion.

8 . A method as claimed in claim 1 comprising, in said processor:
obtaining a spatially resolved candidate value for said first value of said at least one scan parameter, that is spatially resolved in said first subregion;
determining a value of the physical variable dependent on said spatially resolved candidate value of said first value of said at least one scan parameter;
making a threshold value comparison between the determined value of the physical variable and the predetermined threshold value, thereby obtaining a comparison result;
dependent on said comparison result, selectively adjusting said spatially resolved candidate value in the first subregion with adjustment by a larger amount the greater a distance of a respective position in said first subregion is from said second subregion; and
also obtaining a candidate value of said second value of said at least one scan parameter in said second subregion and using said candidate value as said second value said at least one scan parameter.

9 . A method as claimed in claim 1 comprising:
operating said MR scanner to obtain said acquired MR data by, in said scan sequence, radiating at least one radio-frequency pulse having a duration, an average energy and an amplitude, activating at least one gradient pulse that produces a gradient field having an average field strength and a rate of change of said field strength, providing a dead time between successive acquisitions of the acquired MR data, and acquiring said acquired MR data during an echo time and from at least one slice of the examination object; and
selecting said at least one scan parameter from the group consisting of the amplitude and average energy of said at least one radio-frequency pulse, the duration and the average energy of said at least one radio-frequency pulse, the dead time and the average energy of said radio-frequency pulse, a pulse configuration and the average energy of said at least one radio-frequency pulse, a transmission array setting for radiating said at least one radio-frequency pulse and the average energy of said at least one radio-frequency pulse, a number of said radio-frequency pulses and the average energy thereof, the amplitude of said gradient pulse and the average field strength of said gradient field, the dead time and the average field strength of the gradient field, a duration of said gradient pulse and the average field strength of the gradient field, a pulse configuration of said gradient pulse and said average field strength of said gradient field, a gradient offset current that compensates for a field inhomogeneity of a basic magnetic field in said MR scanner and the average field strength of the gradient field, said echo time and the average field strength of the gradient field, a slice thickness of said at least one slice and the average rate of change of the field strength of the gradient field, the echo time and the average rate of change of the field strength of the gradient field, the rate of change of an amplitude of said gradient pulse and the average rate of change of the field strength of the gradient field, the dead time and the average rate of change of the gradient field, and a plurality of different slices from which said acquired MR data are acquired and the average energy of said at least one radio-frequency pulse.

10 . A method as claimed in claim 9 comprising selecting said gradient pulse from the group consisting of a spoiler gradient pulse and a preparation gradient pulse.

11 . A method as claimed in claim 1 comprising:
operating said MR scanner to execute said scan sequence with a repetition time for a plurality of slices in the examination region; and
selecting said physical variable to describe an integration over time that occurs on a time scale that is at least as large as said repetition time.

12 . A method as claimed in claim 1 comprising predetermining said predetermined threshold value dependent on a technical efficiency of said MR scanner.

13 . A method as claimed in claim 1 comprising determining said predetermined threshold value dependent on a physiological limitation of the examination object.

14 . A me

Assignees

• Siemens Ag

Inventors

• Feiweier Thorsten

Classifications

• G01R33/288

  Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room · CPC title

• G01R33/4835

  of multiple slices · CPC title

• G01R33/546

  Interface between the MR system and the user, e.g. for controlling the operation of the MR system or for the design of pulse sequences · CPC title

• G01R33/543 Primary

  Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription (G01R33/546 takes precedence) · CPC title

• G01R33/36

  Electrical details, e.g. matching or coupling of the coil to the receiver · CPC title