Real‐time simultaneous shim and motion measurement and correction in glycoCEST MRI using double volumetric navigators (DvNavs)

Purpose CEST MRI allows for indirect detection of molecules with exchangeable protons, measured as a reduction in water signal because of continuous transfer of saturated protons. CEST requires saturation pulses on the order of a second, as well as repeated acquisitions at different offset frequenci...

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Bibliographic Details
Published in:Magnetic resonance in medicine 2019-04, Vol.81 (4), p.2600-2613
Main Authors: Simegn, Gizeaddis L., Van der Kouwe, Andre J.W., Robertson, Frances C., Meintjes, Ernesta M., Alhamud, Ali
Format: Article
Language:English
Subjects:
Adult
Algorithms
B0 correction
CEST
chemical exchange saturation transfer
double volumetric navigator
DvNav
Glycogen
Healthy Volunteers
Humans
Hydroxyl groups
Image Enhancement - methods
Image Interpretation, Computer-Assisted - methods
Image Processing, Computer-Assisted - methods
Imaging, Three-Dimensional
In vivo methods and tests
Inhomogeneity
Linear Models
Magnetic Resonance Imaging
Male
Motion
motion correction
Muscle, Skeletal - pathology
Muscles
Navigators
Phantoms, Imaging
Protons
Reproducibility of Results
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Summary:Purpose CEST MRI allows for indirect detection of molecules with exchangeable protons, measured as a reduction in water signal because of continuous transfer of saturated protons. CEST requires saturation pulses on the order of a second, as well as repeated acquisitions at different offset frequencies. The resulting extended scan time makes CEST susceptible to subject motion, which introduces field inhomogeneity, shifting offset frequencies and causing distortions in CEST spectra that resemble true CEST effects. This is a particular problem for molecules that resonate close to water, such as hydroxyl group in glycogen. To address this, a technique for real‐time measurement and correction of motion and field inhomogeneity is proposed. Methods A CEST sequence was modified to include double volumetric navigators (DvNavs) for real‐time simultaneous motion and shim correction. Phantom tests were conducted to investigate the effects of motion and shim changes on CEST quantification and to validate the accuracy of DvNav motion and shim estimates. To evaluate DvNav shim and motion correction in vivo, acquisitions including 5 experimental conditions were performed in the calf muscle of 2 volunteers. Results Phantom data show that DvNav‐CEST accurately estimates frequency and linear gradient changes because of motion and corrects resulting image distortions. In addition, DvNav‐CEST improves CEST quantification in vivo in the presence of motion. Conclusion The proposed technique allows for real‐time simultaneous motion and shim correction with no additional scanning time, enabling accurate CEST quantification even in the presence of motion and field inhomogeneity.
ISSN:0740-3194
1522-2594
DOI:10.1002/mrm.27597