Method and magnetic resonance system for acquiring magnetic resonance data in a predetermined region of an examination subject

Patent metadata

Field	Value
Publication number	US-9151816-B2
Application number	US-201213564137-A
Country	US
Kind code	B2
Filing date	Aug 1, 2012
Priority date	Aug 1, 2011
Publication date	Oct 6, 2015
Grant date	Oct 6, 2015

Abstract

In a method and a magnetic resonance system to acquire MR data in a predetermined region within an examination subject, a first three-dimensional volume segment is selectively excited with an RF excitation pulse, this first volume segment including the predetermined region and having a first thickness along a first thickness direction. A selective refocusing pulse is activated in order to selectively refocus a second volume segment. The second volume segment likewise includes the predetermined region and has a second thickness along a second thickness direction orthogonal to the first thickness direction. The following sub-steps are implemented repeatedly in succession: a non-selective refocusing pulse is activated. Two phase coding gradients and an additional magnetic field gradient are activated for spatial coding, and the MR data are read out while the additional magnetic field gradient is activated.

First claim

We claim as our invention:

1. A method to acquire magnetic resonance (MR) data from a predetermined region within an examination subject, comprising:
from a computerized control unit, operating a MR data acquisition unit to selectively excite a first three-dimensional volume segment of an examination subject by radiating a radio-frequency (RF) excitation pulse, said first volume segment comprising a predetermined region and said first volume segment having a first thickness along a first thickness direction;
from said computerized control unit, operating said MR data acquisition unit to activate a selective refocusing pulse that selectively refocuses a second volume segment of the examination subject, said second volume segment also comprising said predetermined region, and said second volume segment having a second thickness along a second thickness direction that is orthogonal to said first thickness direction;
from said computerized control unit, repeatedly and in succession operating said MR data acquisition unit by activating a non-selective refocusing pulse, followed by activating two phase coding gradients and an additional magnetic field gradient for spatial coding of MR signals resulting from nuclear spins in said predetermined region excited by said RF excitation pulse, and reading out said MR signals while said additional magnetic field gradient is activated; and
making said MR signals available in an MR data file from said computerized control unit.

2. A method as claimed in claim 1 comprising:
from said computerized control unit, operating said MR data acquisition unit to activate said phase coding gradients and said additional magnetic field gradient respectively orthogonally to each other in pairs, and with one of said phase coding gradients being directed along said first thickness direction.

3. A method as claimed in claim 1 comprising:
from said computerized control unit, operating said MR data acquisition unit to activate a first magnetic field gradient during said selected RF excitation pulse, and to activate a second magnetic field gradient during activation of said selective refocusing pulse, with said first magnetic field gradient and said second magnetic field gradient being orthogonal to each other.

4. A method as claimed in claim 1 comprising:
from said computerized control unit, radiating said selected RF excitation pulse with a configuration that excites nuclear spins in a cuboid forming said predetermined region, said cuboid having a thickness corresponding to said first thickness along said first thickness direction, and said cuboid having a further thickness corresponding to said second thickness along said second thickness direction.

5. A method as claimed in claim 1 comprising:
from said computerized control unit, operating said MR data acquisition unit to radiate the non-selective refocusing pulses with respective flip angles configured to produce a predetermined signal strength of said MR signals upon readout thereof, dependent on a known substance that occupies said predetermined region.

6. A method as claimed in claim 1 comprising:
from said computerized control unit, operating said MR data acquisition unit to activate at least one rephasing gradient before and after activating said selective refocusing pulse, with said at least one rephasing gradient being directed along said second thickness direction.

7. A method as claimed in claim 6 comprising:
from said computerized control unit, operating said MR data acquisition unit to also radiate at least one rephasing gradient directed along said first thickness direction.

8. A method as claimed in claim 6 comprising:
from said computerized control unit, operating said MR data acquisition unit to also radiate at least one rephasing gradient along a direction that is orthogonal to both said first thickness and said second thickness direction.

9. A method as claimed in claim 1 comprising:
from said computerized control unit, entering said MR signals into a k-space memory representing k-space, comprising a plurality of k-space segments; and
for each of said k-space segments, acquiring MR signals and entering the acquired MR signals into the respective k-space segment by operating said MR data acquisition unit from said computerized control unit to flip magnetization of nuclear spins in said predetermined region by +90° with said RF excitation pulse, and reading out first MR signals and entering said MR signals into the respective k-space segment, subsequently flipping said magnetization by −90° with said RF excitation pulse, and reading out second MR signals and entering said second MR signals into the respective k-space segment and, in said computerized control unit, averaging said first and second MR signals in the respective k-space segment in order to produce MR data for the respective k-space segment.

10. A magnetic resonance (MR) system comprising:
an MR data acquisition unit;
a computerized control unit;
said computerized control unit being configured to operate a MR data acquisition unit to selectively excite a first three-dimensional volume segment of an examination subject by radiating a radio-frequency (RF) excitation pulse, said first volume segment comprising a predetermined region and said first volume segment having a first thickness along a first thickness direction;
from said computerized control unit being configured to operate said MR data acquisition unit to activate a selective refocusing pulse that selectively refocuses a second volume segment of the examination subject, said second volume segment also comprising said predetermined region, and said second volume segment having a second thickness along a second thickness direction that is orthogonal to said first thickness direction;
from said computerized control unit being configured to repeatedly and in succession operate said MR data acquisition unit by activating a non-selective refocusing pulse, followed by activating two phase coding gradients and an additional magnetic field gradient for spatial coding of MR signals resulting from nuclear spins in said predetermined region excited by said RF excitation pulse, and reading out said MR signals while said additional magnetic field gradient is activated; and
said computerized control unit being configured to make said MR signals available in an MR data file from said computerized control unit.

11. A non-transitory, computer-readable data storage medium encoded with programming instructions that, when said data storage medium is loaded into a computerized control and evaluation system of an MR system that also comprises an MR data acquisition unit, cause said control and evaluation system to operate said MR data acquisition unit to:
selectively excite a first three-dimensional volume segment of an examination subject by radiating a radio-frequency (RF) excitation pulse, said first volume segment comprising a predetermined region and said first volume segment having a first thickness along a first thickness direction;
activate a selective refocusing pulse that selectively refocuses a second volume segment of the examination subject, said second volume segment also comprising said predetermined region, and said second volume segment having a second thickness along a second thickness direction that is orthogonal to said first thickness direction;
repeatedly and in succession activate a non-selective refocusing pulse, followed by activating two phase coding gradients and an additional magnetic field gradient for spatial coding of MR signals resulting from nuclear spins in said predetermined region excited by said RF excitation pulse, and read out said MR signals while said

Assignees

• Fautz Hans-Peter
• Paul Dominik
• Siemens Ag

Inventors

• Fautz Hans-Peter
• Paul Dominik

Classifications

• G01R33/56545 Primary

  caused by finite or discrete sampling, e.g. Gibbs ringing, truncation artefacts, phase aliasing artefacts · CPC title

• G01R33/4822

  in three dimensions · CPC title

• G01R33/4833

  using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices · CPC title