Magnetic resonance imaging

Patent metadata

Field	Value
Publication number	US-10401453-B2
Application number	US-201715712942-A
Country	US
Kind code	B2
Filing date	Sep 22, 2017
Priority date	Sep 22, 2017
Publication date	Sep 3, 2019
Grant date	Sep 3, 2019

Abstract

A method of acquiring magnetic resonance imaging (MRI) data from an MRI scan of an object includes generating a number of excitation sequences by, in order: generating an excitation pulse, generating an imaging magnetic field gradient, and generating a spoiler magnetic field gradient. MRI data is acquired during the generation of the spoiler magnetic field gradients. The spoiler magnetic field gradients are selected such that, during each excitation sequence, substantially the same k-space trajectory is traversed during the generation of the spoiler magnetic field gradient.

First claim

The invention claimed is:

1. A method of acquiring magnetic resonance imaging (MRI) data in the frequency domain (k-space) from an MRI scan of an object, the method comprising:
generating a plurality of excitation sequences, wherein generating each excitation sequence includes, in order, generating an imaging magnetic field gradient, and generating a spoiler magnetic field gradient; and
acquiring MRI data during the generation of the spoiler magnetic field gradients;
wherein the spoiler magnetic field gradients are selected such that, during each excitation sequence, the same part of the frequency domain is re-sampled during the generation of the spoiler magnetic field gradient.

2. The method according to claim 1 , wherein said same part of the frequency domain contains higher spatial frequencies than does any part of the frequency domain sampled during any part of a said excitation sequence other than during the generation of the spoiler magnetic field gradient.

3. The method according to claim 1 , wherein generating each excitation sequence includes generating a frequency-encode magnetic field gradient along a first spatial axis, and the method includes generating the spoiler magnetic field gradient along the first spatial axis.

4. The method according to claim 3 wherein the polarity of the spoiler magnetic field gradient is the same as the polarity of the frequency-encode magnetic field gradient immediately prior to generating the spoiler magnetic field gradient.

5. The method according to claim 3 , wherein generating the imaging magnetic field gradient comprises generating a phase encode magnetic field gradient along a second spatial axis, and wherein generating each excitation sequence further comprises generating a re-wind magnetic field gradient along the second spatial axis during the generation of the spoiler magnetic field gradient, wherein the duration of the spoiler magnetic field gradient exceeds the duration of the re-wind magnetic field gradient along the second spatial axis.

6. The method according to claim 5 , wherein generating each excitation sequence further comprises generating a re-wind magnetic field gradient along the third spatial axis during the generation of the spoiler magnetic field gradient, wherein the duration of the spoiler magnetic field gradient exceeds the duration of the re-wind magnetic field gradient along the third spatial axis.

7. The method according to claim 6 , wherein the MRI data is acquired after the generation of the re-wind magnetic field gradients.

8. The method according to claim 5 , wherein the MRI data is acquired after the generation of the re-wind magnetic field gradients.

9. The method according to claim 3 , wherein the frequency-encode magnetic field gradient is arranged to generate a gradient echo.

10. The method according to claim 9 , wherein the frequency-encode magnetic field gradient is arranged to generate multiple gradient echoes.

11. The method according to claim 1 wherein generating the imaging magnetic field gradient comprises generating a frequency-encode magnetic field gradient along a first spatial axis, generating a phase encode magnetic field gradient along a second spatial axis, and generating a slice-select magnetic field gradient along a third spatial axis, wherein generating the spoiler magnetic field gradient comprises generating the spoiler magnetic field gradient along the first spatial axis.

12. The method according to claim 1 , wherein acquiring the MRI data comprises digitizing MRI signals received during the spoiler magnetic field gradients using an analogue-to-digital converter (ADC).

13. The method according to claim 1 , further comprising processing the MRI data so as to determine whether motion has occurred in the object represented by the MRI data.

14. The method according to claim 13 , wherein the acquiring the MRI data comprises acquiring a plurality of data sets corresponding to said plurality of excitation sequences, and the processing the MRI data comprises identifying any of the plurality of excitation sequences in which object motion has occurred.

15. The method according to claim 14 , wherein the processing the MRI data comprises comparing the values of the MRI data to a predetermined threshold value, and for any of the MRI data values that exceed the predetermined threshold value, the method further comprises identifying the excitation sequence associated with the MRI data value as being an excitation sequence in which object motion occurred.

16. The method according to claim 14 , wherein the acquiring the MRI data comprises acquiring a plurality of data sets each having a given number of MRI data values, and the processing the MRI data comprises replacing the given number of MRI data values for each of the data sets with a single representative data value.

17. The method according to claim 16 , wherein for each of the plurality of data sets, the single representative value is the standard deviation across said given number of MRI data values.

18. The method according to claim 16 , further comprising normalizing the single representative data values to obtain a corresponding normalized data values.

19. The method according to claim 16 , further comprising: comparing the normalized data values to a predetermined threshold value, and for any of the normalized data values that exceed the predetermined threshold value, the method further comprises identifying the excitation sequence associated with the normalized data value as being an excitation sequence in which object motion occurred.

20. A non-transitory, computer readable data storage medium encoded with programming instructions, said storage medium being loaded into a computer of a magnetic resonance imaging (MRI) apparatus, and said programming instructions causing said computer to:
generate a plurality of excitation sequences, wherein generating each excitation sequence includes, in order, generating an imaging magnetic field gradient, and generating a spoiler magnetic field gradient;
acquire MRI data during the generation of the spoiler magnetic field gradients; and
wherein the spoiler magnetic field gradients are selected such that, during each excitation sequence, the same part of the frequency domain is re-sampled during the generation of the spoiler magnetic field gradient.

21. A magnetic resonance imaging system comprising a magnet assembly for establishing a magnetic field, at least one gradient coil, and a receiver coil, the MRI system being configured to:
generate a plurality of excitation sequences by controlling, in order, the at least one gradient coil to generate an imaging magnetic field gradient and, the at least one gradient coil to generate a spoiler magnetic field gradient;
control the receiver coil to acquire MRI data during the generation of the spoiler magnetic field gradients; and
wherein the spoiler magnetic field gradients are selected such that, during each excitation sequence, the same part of the frequency domain is re-sampled during the generation of the spoiler magnetic field gradient.

22. A method for identifying spatial motion of an object during the acquisition of magnetic resonance imaging (MRI) data thereof by an MRI apparatus, comprising:
providing first MRI data representing an object in motion during an MRI scan thereof by said MRI apparatus, the first MRI data comprising a number M of data sets each having a number P of MRI data values, wherein each of the M data sets is associated with an excit

Assignees

• Siemens Healthcare Ltd
• Siemens Healthcare Gmbh
• Univ London

Inventors

• Dragonu Iulius
• Buckley Craig
• Meyer Heiko
• Weiskopf Nikolaus
• Callaghan Martina
• Papp Daniel

Classifications

• G01R33/5676

  Gating or triggering based on an MR signal, e.g. involving one or more navigator echoes for motion monitoring and correction · CPC title

• G01R33/4822

  in three dimensions · CPC title

• G01R33/482 Primary

  using a Cartesian trajectory · CPC title

• G01R33/56509

  due to motion, displacement or flow, e.g. gradient moment nulling (G01R33/567 takes precedence) · CPC title

• G01R33/3621

  NMR receivers or demodulators, e.g. preamplifiers, means for frequency modulation of the MR signal using a digital down converter, means for analog to digital conversion [ADC] or for filtering or processing of the MR signal such as bandpass filtering, resampling, decimation or interpolation · CPC title