EPI ghost correction involving sense

• US 10,241,184 B2
• Filed: 03/20/2015
• Issued: 03/26/2019
• Est. Priority Date: 03/28/2014
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Jurrissen, Michel Paul Jurriaan, Groen, Johannes Petrus, Fuderer, Miha
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): Rhodes-Vivour, Temilade
• Application Number:
  US15/128,131
• Publication Number:
  US 20170108571A1
• Time in Patent Office: 1,467 Days
• CPC Class Codes: A61B 2217/00 General characteristics of surgical instruments
• CPC Class Codes: A61K 6/00 Preparations for dentistry
• CPC Class Codes: G01R 1/00 Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00 constructional details particular to electromechanical arrangements for measuring the electric consumption G01R11/02
• CPC Class Codes: G01R 33/4818 MR characterised by data acquisition along a specific k-space trajectory or by the temporal order of k-space coverage, e.g. centric or segmented coverage of k-space
• CPC Class Codes: G01R 33/5611 Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE structural details of arrays of sub-coils G01R33/3415
• CPC Class Codes: G01R 33/5616 using gradient refocusing, e.g. EPI
• CPC Class Codes: G01R 33/56545 caused by finite or discrete sampling, e.g. Gibbs ringing, truncation artefacts, phase aliasing artefacts
• CPC Class Codes: G01R 33/56554 caused by acquiring plural, differently encoded echo signals after one RF excitation, e.g. correction for readout gradients of alternating polarity in EPI
• CPC Class Codes: G01R 33/583 Calibration of signal excitation or detection systems, e.g. for optimal RF excitation power or frequency G01R33/246 takes precedence

Abstract

In an EPI acquisition sequence for magnetic resonance signals k-space is scanned along sets of lines in k-space along opposite propagation directions, e.g. odd and even lines in k-space. Phase errors that occur due to the opposite propagation directions are corrected for in a SENSE-type parallel imaging reconstruction. The phase error distribution in image space may be initially estimated, calculated form the phase difference between images reconstructed from magnetic resonance signals acquired from the respective sets of k-space lines, or from an earlier dynamic.

Claims

1. A magnetic resonance imaging method, comprising;

employing an echo-planar imaging (EPI) acquisition sequence which includes sampling of k-space for magnetic resonance signals to collect;

an ltr-data set (m_ltr) reconstructed from lines in k-space scanned along a positive traversal direction in k-space, and

an rtl-data set (m_rtl) reconstructed from lines in k-space scanned along a negative traversal direction in k-space,

the magnetic resonance signals of the ltr-data set and the rtl-data set being acquired with several RF receiver antennae having spatial sensitivity profiles, the method further comprising;

accessing a spatial phase error distribution for the ltr-data set and for the rtl-data set,

forming an ltr-encoding matrix (S_ltr) from (i) a phase encoding of the lines in k-space scanned along the positive traversal direction in k-space, (ii) a spatial phase error distribution for the ltr-data set, and (iii) spatial coil sensitivity profiles,

forming an rtl-encoding matrix from (S_rtl) (i) a phase encoding of the lines in k-space scanned along the negative traversal direction in k-space, (ii) a spatial phase error distribution for the rtl-data set, and (iii) the spatial coil sensitivity profiles,

combining the ltr-encoding matrix and the rtl-encoding matrix into a global encoding matrix S, and

reconstructing a diagnostic magnetic resonance image (p) by resolving an encoding relationship between the ltr-data set and the rtl-data set for the pixel values (p_j(r)) of the magnetic resonance image;

2. The magnetic resonance imaging method of claim 1, in which the phase corrected unfolded ltr-image and phase corrected unfolded rtl-image are employed to derive a more accurate subtracted phase image which provides a spatial phase error distribution of a current iteration, which, in turn is employed in a next iteration to again correct for phase errors in the unfolded ltr-image and unfolded rtl-image.

3. The magnetic resonance imaging method as claimed in claim 1 wherein the initial spatial phase error distribution is measured in the calibration stage in which an EPI acquisition is done having one set of lines in k-space each scanned first along a positive propagation direction and then along a negative propagation direction, and having another set of lines in k-space each scanned first along the negative propagation direction and then along the positive propagation direction.

4. The magnetic resonance imaging method of claim 3 in which a line along zero-phase encoding is scanned in k-space first along a positive traversal, then along a negative traversal and finally again along a positive traversal.

5. A computer program for controlling a magnetic resonance examination system and comprising instructions stored on a non-transitory computer readable medium, which when executed causes the magnetic resonance examination system to:

apply an echo-planar imaging (EPI) acquisition sequence which includes sampling of k-space for magnetic resonance signals to collect;

an ltr-data set (m_ltr) reconstructed from lines in k-space scanned along a positive traversal direction in k-space, and

an rtl-data set (m_rtl) reconstructed from lines in k-space scanned along a negative traversal direction in k-space,

acquire magnetic resonance signals of the ltr-data set and the rtl-data set with several RF receiver antennae having spatial sensitivity profiles,

access spatial phase error distributions for the ltr-data set and for the rtl-data set,

form an ltr-encoding matrix (S_ltr) from a phase encoding of the lines in k-space scanned along the positive traversal direction in k-space, (ii) a spatial phase error distribution for the ltr-data set, and (iii) the spatial sensitivity profiles,

form an rtl-encoding matrix from (S_rtl) (i) a phase encoding of the lines in k-space scanned along the negative traversal direction in k-space, (ii) a spatial phase error distribution for the rtl-data set, and (iii) the spatial sensitivity profiles,

combine the ltr-encoding matrix and the rtl-encoding matrix into a global encoding matrix S,

reconstruct a magnetic resonance image (p) by resolving an encoding relationship between the ltr-data set and the rtl-data set and pixel values (p_j(r)) of the magnetic resonance image;