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Magn Reson Med. 2016 Dec 8. doi: 10.1002/mrm.26569. [Epub ahead of print]

Method of B0 mapping with magnitude-based correction for bipolar two-point Dixon cardiac MRI.

Author information

  • 1Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
  • 2Department of Radiology and Biomedical Imaging, Yale Medical School, New Haven, Connecticut, USA.
  • 3Department of Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.

Abstract

PURPOSE:

The conventional two-point (2pt) Dixon technique explicitly estimates B0 map by performing phase unwrapping. When signal loss, phase singularity, artifacts, or spatially isolated regions corrupt the measured phase images, this unwrapping-based technique will face difficulty. This work aims to improve the reliability of B0 mapping by performing unwrapping error correction.

METHOD:

To detect the unwrapping-caused phase errors, we determined a magnitude-based fat/water mask and used it as reference to identify pixels being mismatched by the phase-based mask, which was derived from the B0-corrected phase term of the Hermitian product between echoes. Then, we corrected the afore-determined phase error on a region-by-region basis. We tested the developed method with nine patients' data, and the results were compared with a well-established region-growing technique.

RESULTS:

By adding the step to correct unwrapping-caused error, we improved the robustness of B0 mapping, resulting in better fat-water separation when compared with the conventional 2pt and the phasor-based region-growing techniques.

CONCLUSION:

We showed the feasibility of B0 mapping with bipolar 2pt human cardiac data. The software is freely available to the scientific community. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine.

KEYWORDS:

B0 off-resonance mapping; Dixon MRI; bipolar gradient; dual-echo; phase unwrapping

PMID:
27933641
DOI:
10.1002/mrm.26569
[PubMed - as supplied by publisher]
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