Method to generate an RF excitation pulse to excite an arbitrarily shaped volume, method for targeted excitation of spins within a vessel, and method to create MR angiography images, and magnetic resonance system

Patent metadata

Field	Value
Publication number	US-9615769-B2
Application number	US-201314099034-A
Country	US
Kind code	B2
Filing date	Dec 6, 2013
Priority date	Dec 6, 2012
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

In order to generate an RF excitation pulse together with a gradient curve to excite nuclear spins an arbitrarily shaped volume with a magnetic resonance system, a volume segment is prepared in which the volume is situated, such that only spins within the volume yield an MR signal portion in the subsequent detection of an MR signal. An MR signal is detected from the volume segment along a trajectory of k-space. At least one gradient for scanning k-space along the trajectory is switched during the detection. The RF excitation pulse is generated corresponding to the MR signal detected in a temporally inverted manner, and the gradient curve is generated corresponding to the temporally inverted curve of the at least one gradient to scan k-space.

First claim

I claim as my invention:

1. A method to generate a radio-frequency (RF) excitation pulse together with a gradient curve for a targeted excitation of nuclear spins in an arbitrarily shaped volume, comprising:
from a computerized control unit, operating a magnetic resonance (MR) data acquisition unit in which an examination volume is situated, to prepare a volume segment in said volume to cause only nuclear spins within said volume to contribute to an MR signal in a subsequent detection of said magnetic resonance signal;
from said control unit, operating said MR data acquisition unit to detect said MR signal from said volume segment while activating at least one gradient that causes data representing the detected magnetic resonance signal to be entered into an electronic memory organized as k-space, along a trajectory in k-space defined by said at least one gradient, said MR signal having an MR signal curve with respect to time and said at least one gradient having a gradient curve with respect to time; and
in said control unit, automatically generating said RF excitation pulse for said targeted excitation as an RF pulse having an RF pulse curve that is a temporal inversion of said MR signal curve, and generating said gradient curve for said targeted excitation as a gradient having a gradient curve that is a temporal inversion of the gradient curve of said at least one gradient activated during detection of said MR signal, and making an electronic signal available at an output of said control unit embodying said RF excitation pulse and said gradient curve for said targeted excitation in a form usable to operate said MR data acquisition unit to implement said targeted excitation.

2. A method as claimed in claim 1 comprising:
preparing said volume by saturating or inverting said nuclear spins in said volume segment; and detecting said MR signal by detecting MR signal contributions produced by nuclear spins in a flowing medium that have flowed into said volume after preparing said volume segment.

3. A method as claimed in claim 1 comprising generating said RF excitation pulse for said targeted excitation with a flip angle that is less than 30°.

4. A method as claimed in claim 1 comprising:
generating said RF excitation pulse for said targeted excitation with a flip angle that is greater than or equal to 30°; and
in said control unit, adapting said RF excitation pulse for said targeted excitation dependent on a magnitude of said flip angle and dependent on the detected MR signal in order to excite only nuclear spins in said volume.

5. A method as claimed in claim 1 wherein said MR data acquisition unit comprises multiple RF antennas, and wherein said method comprises:
detecting said MR signal with each of said RF antennas, thereby resulting in a plurality of respectively detected MR signals; and
in said control unit, generating said RF excitation pulse for said targeted excitation as a plurality of RF pulses to be respectively radiated by said multiple RF antennas, with each RF pulse to be radiated by each RF antenna being a temporal inversion of the respective MR signal detected by the respective RF antenna.

6. A method as claimed in claim 1 comprising:
in said control unit, determining said volume segment such that, outside of said volume, said volume segment comprises no additional volume having properties comparable to properties of said volume.

7. A method for targeted excitation of nuclear spins within a blood vessel, comprising:
from a computerized control unit, operating a magnetic resonance (MR) data acquisition unit in which an examination volume is situated, to prepare a volume segment in said volume to cause only nuclear spins within said volume to contribute to an MR signal in a subsequent detection of said MR signal;
from said control unit, operating said MR data acquisition unit to detect said MR signal from said volume segment while activating at least one gradient that causes data representing the detected MR signal to be entered into an electronic memory organized as k-space, along a trajectory in k-space defined by said at least one gradient, said MR signal having an MR signal curve with respect to time and said at least one gradient having a gradient curve with respect to time;
in said control unit, automatically generating said RF excitation pulse for said targeted excitation as an RF pulse having an RF pulse curve that is a temporal inversion of said MR signal curve, and generating said gradient curve for said targeted excitation as a gradient having a gradient curve that is a temporal inversion of the gradient curve of said at least one gradient activated during detection of said MR signal; and
from said control unit operating said MR data acquisition unit to implement said targeted excitation by radiating said RF excitation pulse and activating said gradient curve.

8. A method as claimed in claim 7 wherein said MR data acquisition unit comprises multiple RF antennas, and wherein said method comprises:
detecting said MR signal with each of said RF antennas, thereby resulting in a plurality of respectively detected MR signals;
in said control unit, generating said RF excitation pulse for said targeted excitation as a plurality of RF pulses to be respectively radiated by said multiple RF antennas, with each RF pulse to be radiated by each RF antenna being a temporal inversion of the respective MR signal detected by the respective RF antenna; and
radiating said plurality of RF pulses respectively from said multiple of RF antennas in said targeted excitation.

9. A method to generate a magnetic resonance (MR) angiography image of an examination subject, comprising:
from a computerized control unit, operating an MR data acquisition unit in which an examination volume is situated, to prepare a vessel in said volume to cause only nuclear spins within said vessel to contribute to an MR signal in a subsequent detection of said MR signal;
from said control unit, operating said MR data acquisition unit to detect said MR signal from said vessel while activating at least one gradient that causes data representing the detected MR signal to be entered into an electronic memory organized as k-space, along a trajectory in k-space defined by said at least one gradient, said MR signal having an MR signal curve with respect to time and said at least one gradient having a gradient curve with respect to time; and
in said control unit, automatically generating said RF excitation pulse for a subsequent targeted excitation of said vessel as an RF pulse having an RF pulse curve that is a temporal inversion of said MR signal curve, and generating said gradient curve for said targeted excitation of said vessel as a gradient having a gradient curve that is a temporal inversion of the gradient curve of said at least one gradient activated during detection of said MR signal;
from said control unit, operating said MR data acquisition unit by radiating said RF excitation pulse and activating said gradient curve to implement said targeted excitation of said vessel, and acquiring MR data following said targeted excitation; and
in a processor, reconstructing an angiographic image of said vessel from said MR data acquired following said targeted excitation.

10. A method as claimed in claim 9 wherein said MR data acquisition unit comprises multiple RF antennas, and wherein said method comprises:
detecting said MR signal with each of said RF antennas, thereby resulting in a plurality of respectively detected MR signals; and
in said control unit, generating said RF excitation pulse for said targeted excitation as a plurality of RF pulses to be respectively radiated by said multiple RF antennas, with each RF pulse to

Assignees

• Fautz Hans-Peter
• Siemens Ag

Inventors

• Fautz Hans-Peter

Classifications

• A61B5/055 Primary

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• G01R33/5635

  Angiography, e.g. contrast-enhanced angiography [CE-MRA] or time-of-flight angiography [TOF-MRA] · CPC title

• G01R33/56366

  Perfusion imaging · CPC title

• A61B5/004

  adapted for image acquisition of a particular organ or body part (A61B5/0082 takes precedence; arrangements for optical scanning A61B5/0062) · CPC title

• G01R33/48

  NMR imaging systems · CPC title