WO2003098267A1 - Suppression d'especes chimiques dans l'imagerie par resonance magnetique - Google Patents

Suppression d'especes chimiques dans l'imagerie par resonance magnetique Download PDF

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Publication number
WO2003098267A1
WO2003098267A1 PCT/US2003/015241 US0315241W WO03098267A1 WO 2003098267 A1 WO2003098267 A1 WO 2003098267A1 US 0315241 W US0315241 W US 0315241W WO 03098267 A1 WO03098267 A1 WO 03098267A1
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WO
WIPO (PCT)
Prior art keywords
chemical species
method defined
data set
trajectory
space
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Application number
PCT/US2003/015241
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English (en)
Inventor
Christopher A. Flask
Jonathan S. Lewin
Hisamoto Moriguchi
Claudia Hillebrand
Jeffrey L. Duerk
Brian M. Dale
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Case Western Reserve University
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Priority to AU2003234577A priority Critical patent/AU2003234577A1/en
Publication of WO2003098267A1 publication Critical patent/WO2003098267A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/4828—Resolving the MR signals of different chemical species, e.g. water-fat imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G01R33/5607—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reducing the NMR signal of a particular spin species, e.g. of a chemical species for fat suppression, or of a moving spin species for black-blood imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/4818—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
    • G01R33/4824—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 using a non-Cartesian trajectory

Definitions

  • the present invention relates to a chemical species suppression in Magnetic Resonance Imaging (MRI). More particularly, the invention relates to a method for species suppression using two or more trajectories having different echo times (TEs) and covering substantially mutually exclusive portions of k-space.
  • MRI Magnetic Resonance Imaging
  • TEs echo times
  • a number of suppression techniques have been implemented to differentiate chemical species in MRI imaging.
  • Suppression techniques known as fat suppression
  • fat suppression are often used to in MRI to differentiate fat from water in an imaged object.
  • the majority of fat suppression techniques require specialized Radio Frequency RF excitation schema to selectively excite water protons or saturate fat protons.
  • Binomial and CHESS are known excitation schema which are extremely effective at 1.5T.
  • SAR Specific Absorption Rate
  • Known multi-point Dixon fat suppression methods take advantage of the relative difference in precession frequency of fat and water to create water and fat images from at least two full acquisitions.
  • Higher order Dixon methods can be used to correct for field inhomogeneities and/or susceptibility artifacts in the fat suppressed images.
  • Dixon fat suppression is obtained without specialized RF excitation pulses, thereby eliminating the SAR constraints of binomial and CHESS excitations.
  • the multi-point Dixon methods significantly extend the overall imaging time by requiring multiple acquisitions of the some of the same portions of k-space. Spiral imaging is a widely used non-uniform data acquisition technique in MRI.
  • spsp spatially spectrally selective excitation RF pulses
  • the invention includes acquiring a first data set corresponding to a first echo time (TE) and having a first trajectory, acquiring a second data set corresponding to a second TE and having a second trajectory, wherein a substantial majority of the second trajectory covers k- space not covered by the first trajectory, and combining the first and second data sets to suppress the second chemical species.
  • the method includes generating an MRI image including the first chemical species and suppressing the second chemical species.
  • the method includes generating at least one pulse sequence using a first TE for the first data set and a second TE for the second data set.
  • Fig. 1 illustrates steps of the invention
  • Fig. 2 illustrates alternating radial k-space trajectories in accordance with the invention
  • Fig. 3 illustrates interleaved reverse spiral k-space trajectories in accordance with the invention.
  • a method for chemical species suppression in MRI is shown generally at 10.
  • the method includes generating a pulse sequence at 12 using a first echo time (TE) for a first data set, the first data set having a first k-space trajectory, and using a second TE for a second data set, the second data set having a second k-space trajectory.
  • the generating step at 12 can include generating one pulse sequence using different TEs, or more than one pulse sequence using different TEs.
  • the method 10 also includes acquiring the first data set and the second data set at 14, wherein a substantial majority of the second trajectory covers k-space not covered by the first trajectory as will be described in farther detail below.
  • the first and second data sets can be acquired in a single acquisition, or in separate acquisitions.
  • the second TE is set in the generating step at 12 above such that the magnetization of the second chemical species in the second data set is out of phase from its orientation in the first data set.
  • the method 10 also includes combining the first and second data sets to suppress one of the chemical species at 16.
  • the method 10 can also include generating an MR image at 18 including one of the chemical species and suppressing the other of the chemical species. Any suitable known reconstruction method can be used to generate the MR image at 18.
  • any suitable pulse sequence with a first TE corresponding to a first data set having a first trajectory and a second TE corresponding to a second data set having second trajectory can be used, wherein a substantial majority (typically more than 99%) of all of the second trajectory covers k-space not covered by the first trajectory.
  • the first chemical species is water and the second chemical species is fat.
  • the first chemical species can be fat and the second chemical species can be water.
  • the first and second chemical species can be any other suitable chemically shifted chemical species.
  • the pulse sequence generated at 12 can be for a steady-state radial sequence for generating radial k-space projections shown generally at 20.
  • the pulse sequence uses alternating TEs, the first TE corresponding to a first data set for producing a first trajectory including even radial k-space projections shown using solid lines at 22.
  • the second TE corresponds to a second data set for producing a second trajectory including odd radial k-space projections shown using dashed lines at 24.
  • the pulse sequence is chosen so that a substantial majority, typically more than 99%, and more preferably more than 99.9%, of the second trajectory 24 covers k-space not covered by the first trajectory 22.
  • the first and second trajectories 22, 24 can cover a small amount of the same k-space which, for example, can be portions of k- space near the origin. However, very little of the two trajectories 22, 24 cover the same k-space, and thus the two trajectories can be considered as substantially mutually exclusive.
  • the first and second trajectories 22 and 24 typically cover less than 5% of the same k-space, preferably less than 1% of the same k-space, and often less than 0.1%) of the same k-space.
  • a Siemens Sonata MR scanner was used although any suitable MR scanner using any suitable magnetic field strength can be used.
  • any other pulse sequence(s) for generating suitable radial trajectories can be used including those using different TEs, TRs, and tip angles.
  • combining the first and second data sets in step 16 results in suppressing the fat signals.
  • the same k-space data can also be used to suppress the water signals with no additional acquisitions by multiplying either the even or the odd k-space lines by -1.
  • the method 10 can also include generating an MR image at 18 including the first chemical species and suppressing the second chemical species using the combined data sets.
  • a known fast look-up table image reconstruction method was used to generate the image at step 18 although any suitable method can be used.
  • the fat suppression obtained from the alternating TE sequence was evaluated by comparing the alternating radial TE sequence with a known radial 2-Point Dixon method using a similar FLASH sequence.
  • Each projection in the radial 2-Point Dixon trajectory was acquired twice along the same k-space trajectory for both the in-phase and out-of-phase echo times.
  • the in-phase and out-of-phase radial 2-Point Dixon data sets were summed prior to image reconstruction to produce fat-suppressed images.
  • PSF point-spread functions
  • a 3ml syringe (8mm ID) was filled with saline and positioned with its long axis aligned with the main magnetic field. It was placed near isocenter in the magnet to act as an approximation to a point signal source for axially acquired images. The sequences were all executed with a 300mm FOV to improve the visualization of the PSFs.
  • On-resonance (i.e., fat-suppressed) PSFs from the radial alternating TE and radial 2 point Dixon sequences for both 128 and 256 projections were generated and compared.
  • the on-resonance radial alternating TE PSFs were obtained by directly gridding and transforming the radial k-space data from the radial alternating TE acquisition of the saline syringe.
  • the on-resonance radial 2-Point Dixon PSFs were generated by summing the in-phase and out-of-phase data sets prior to gridding and image reconstruction.
  • the diameter of the primary ring-lobe in the on-resonance radial alternating TE PSF was found to be twice that of the on-resonance radial 2 point Dixon PSF with the same total number of acquired projections.
  • Off-resonance (i.e., water-suppressed) PSFs from the radial alternating TE sequence with 128 and 256 projections were also generated to examine the effects of incomplete nulling of the fat signal at higher spatial frequencies and TE variation on the level of blurring and streak artifacts.
  • the off-resonance PSFs were obtained by performing a fat reconstruction (water suppression) from the same saline phantom data sets used to create the on-resonance radial alternating TE PSFs.
  • the off-resonance PSFs were reconstructed by multiplying the in-phase projections by -1 prior to gridding.
  • the off-resonance PSFs have primary ring-lobe diameters that are equivalent to the on-resonance radial 2 point Dixon PSFs and smaller than the on-resonance radial alternating TE PSFs.
  • Phantom images from the radial 2-Point Dixon and radial alternating TE sequences with 128 total projections were generated.
  • the streak artifacts from the radial alternating TE sequence were found to be less pronounced and better distributed than the radial 2-Point Dixon images.
  • the CNRs of the phantom images from these two sequences were equivalent at approximately 50, with 256 projections (128 in-phase and 128 out-of-phase).
  • the radial alternating TE sequence provided a marginally better CNR (36 vs. 33) with 128 projections.
  • the radial alternating TE sequence generated in accordance with the invention provided effective fat suppression with improved k-space coverage resulting in reduced artifacts in the reconstructed images as compared to the radial 2-Point Dixon sequence for equal scan times.
  • the reduction in artifacts suggests an opportunity to improve the temporal resolution of the radial 2-Point Dixon method by reducing the total number of views required to obtain the same image quality.
  • the main advantage of improving the temporal resolution of the Dixon methods is to provide a fast and efficient method for fat suppression without the SAR constraints and/or acquisition time increases of CHESS pulses and inversion recovery sequences.
  • the invention can also be extended to other trajectories including but not limited to spiral trajectories, rosette trajectories, and rectilinear echo planar imaging (EPI) to provide suppression of a chemical species in real-time sequences.
  • EPI rectilinear echo planar imaging
  • the invention can also use interleaved reversed spiral imaging generating spiral trajectories shown generally at 30 using alternate TEs for fat suppression.
  • alternate TEs were used for even reversed spiral interleaves, shown as solid lines at 32, and odd reversed spiral interleaves, shown as dashed lines at 34.
  • a 12-interleave reversed spiral sequence was generated on a Siemens 1.5 T Magnetom Sonata (Siemens, Er Weg, Germany), though any suitable number of interleaves may be used.
  • the sequence flip angle, slice thickness and field of view (FA/TH/FOV) were 10°, 10mm, and 210mm, respectively.
  • Separate pulse sequences can be used for the interleaves or a single shot sequence can be used. Further, any other pulse sequence(s) for generating suitable spiral sequences can be used, including those using different TEs, TRs, etc.
  • the TEs used generated fat signals in one data set which were out-of-phase with the fat signals in the other data set, similar to the first embodiment described above.
  • the TE used allowed the fat magnetization to rotate 180° out of phase between successive interleaves. As a result, the fat signal cancels in the lower frequency region of k-space in the combining step 16 in a similar manner as the first embodiment described above.
  • the reversed spiral sequence was designed to oversample the central k-space region by a factor of 2.
  • the radius of the oversampled region was 50% of k max , though any suitable amount of oversampling my be used.
  • oversampling a higher density of data points are generated in a region.
  • a substantial majority of the second trajectory still covers k-space not covered by the first trajectory.
  • the first and second interleaves 32 and 34 typically cover less than 5% of the same k-space, preferably less than 1% of the same k-space, and often less than 0.1% of the same k-space.
  • step 18 demonstrated that the alternating reversed spiral TE sequence provides fat suppression equivalent to the reversed spiral sequence with a spatial-spectral excitation pulse.
  • the chemical species suppression technique using alternating TEs in interleaved reversed spiral imaging is a faster suppression technique than known reversed spiral imaging techniques reducing the acquisition time of the reversed spiral sequences through the elimination of long spatial-spectral excitation RF pulses.
  • the invention can also be used for forward spiral interleaves.
  • the reversed spiral imaging used in accordance with the invention demonstrated some advantages over forward spiral imaging used in accordance with the invention including better resolution and more T2* weighted contrast.
  • the invention has been described with reference to preferred embodiments.

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  • Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Radiology & Medical Imaging (AREA)
  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

L'invention concerne un nouveau procédé amélioré de suppression d'espèces chimiques dans l'imagerie par résonance magnétique (IRM) (10). Ce procédé comprend les étapes consistant: (12) à produire au moins une suite d'impulsion au moyen d'un premier temps d'écho (TE) pour un premier ensemble de données possédant une première trajectoire et d'un second temps d'écho pour un second ensemble de données possédant une seconde trajectoire, (14) à acquérir le premier ensemble de données et le second ensemble de données sans suppression d'espèces chimiques, une grande partie de la seconde trajectoire couvrant l'espace k qui n'est pas couvert par la première trajectoire, (16) à combiner les premier et second ensembles de données aux fins de suppression d'une espèce chimique présente dans les deux ensembles de données et (18) à produire une image IRM représentant les espèces chimiques non supprimées et à supprimer en même temps les espèces chimiques de l'étape précédente.
PCT/US2003/015241 2002-05-17 2003-05-15 Suppression d'especes chimiques dans l'imagerie par resonance magnetique WO2003098267A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003234577A AU2003234577A1 (en) 2002-05-17 2003-05-15 Chemical species suppression in magnetic resonance imaging

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US38130302P 2002-05-17 2002-05-17
US60/381,303 2002-05-17

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WO2003098267A1 true WO2003098267A1 (fr) 2003-11-27

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005114245A1 (fr) * 2004-05-12 2005-12-01 Wisconsin Alumni Research Foundation Irm a separation du signal de la graisse du signal de l'eau au moyen d'une sequence radiale ssfp
US11360171B2 (en) 2019-04-24 2022-06-14 GE Precision Healthcare LLC Method for obtaining magnetic resonance imaging data and magnetic resonance imaging system

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5105152A (en) * 1990-03-22 1992-04-14 The Board Of Trustees Of The Leland Stanford Junior University Magnetic resonance imaging and spectroscopy using a linear class of large tip-angle selective excitation pulses
US5270653A (en) * 1992-04-10 1993-12-14 The Board Of Trustees Of The Leland Stanford Junior University Selective three dimensional excitation for magnetic resonance applications
US5402067A (en) * 1993-08-04 1995-03-28 Board Of Trustees Of The Leland Stanford Junior University Apparatus and method for rare echo imaging using k-space spiral coverage
US5652516A (en) * 1996-01-22 1997-07-29 The Board Of Trustees Of The Leland Stanford Junior University Spectroscopic magnetic resonance imaging using spiral trajectories
US5701074A (en) * 1996-04-25 1997-12-23 Eiscint Ltd. Spectral component separation including unwrapping of the phase via a poisson equation utilizing a weighting map
US6215306B1 (en) * 1999-05-14 2001-04-10 Board Of Trustees Of The Leland Stanford Junior University Magnetic resonance imaging using off-centered spiral trajectories

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5105152A (en) * 1990-03-22 1992-04-14 The Board Of Trustees Of The Leland Stanford Junior University Magnetic resonance imaging and spectroscopy using a linear class of large tip-angle selective excitation pulses
US5270653A (en) * 1992-04-10 1993-12-14 The Board Of Trustees Of The Leland Stanford Junior University Selective three dimensional excitation for magnetic resonance applications
US5402067A (en) * 1993-08-04 1995-03-28 Board Of Trustees Of The Leland Stanford Junior University Apparatus and method for rare echo imaging using k-space spiral coverage
US5652516A (en) * 1996-01-22 1997-07-29 The Board Of Trustees Of The Leland Stanford Junior University Spectroscopic magnetic resonance imaging using spiral trajectories
US5701074A (en) * 1996-04-25 1997-12-23 Eiscint Ltd. Spectral component separation including unwrapping of the phase via a poisson equation utilizing a weighting map
US6215306B1 (en) * 1999-05-14 2001-04-10 Board Of Trustees Of The Leland Stanford Junior University Magnetic resonance imaging using off-centered spiral trajectories

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005114245A1 (fr) * 2004-05-12 2005-12-01 Wisconsin Alumni Research Foundation Irm a separation du signal de la graisse du signal de l'eau au moyen d'une sequence radiale ssfp
US7148685B2 (en) * 2004-05-12 2006-12-12 Wisconsin Alumni Research Foundation Magnetic resonance imaging with fat suppression
US11360171B2 (en) 2019-04-24 2022-06-14 GE Precision Healthcare LLC Method for obtaining magnetic resonance imaging data and magnetic resonance imaging system

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