Improving chemical shift encoded water–fat separation using object-based information of the magnetic field inhomogeneity

Authors

  • Samir D. Sharma,

    Corresponding author
    1. Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
    • Correspondence to: Samir D. Sharma, Ph.D., Department of Radiology, University of Wisconsin, 1122Q WIMR, 1111 Highland Avenue, Madison WI 53705. E-mail: sdsharma2@wisc.edu

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  • Nathan S. Artz,

    1. Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
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  • Diego Hernando,

    1. Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
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  • Debra E. Horng,

    1. Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
    2. Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
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  • Scott B. Reeder

    1. Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA
    2. Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA
    3. Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, USA
    4. Department of Medicine, University of Wisconsin, Madison, Wisconsin, USA
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Abstract

Purpose

The purpose of this work was to improve the robustness of existing chemical shift encoded water–fat separation methods by incorporating object-based information of the B0 field inhomogeneity.

Theory

The primary challenge in water–fat separation is the estimation of phase shifts that arise from B0 field inhomogeneity, which is composed of the background field and susceptibility-induced field. The susceptibility-induced field can be estimated if the susceptibility distribution is known or can be approximated. In this work, the susceptibility distribution is approximated from the source images using the known susceptibility values of water, fat, and air. The field estimate is then demodulated from the source images before water–fat separation.

Methods

Chemical shift encoded source images were acquired in anatomical regions that are prone to water–fat swaps. The images were processed using algorithms from the ISMRM Fat-Water Toolbox, with and without the object-based field map information. The estimates were compared to examine the benefit of using the object-based field map information.

Results

Multiple cases are shown in which water–fat swaps were avoided by using the object-based information of the B0 field map.

Conclusion

Object-based information of the B0 field may improve the robustness of existing chemical shift encoded water–fat separation methods. Magn Reson Med 73:597–604, 2015. © 2014 Wiley Periodicals, Inc.

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