3D phase unwrapping using global expected phase as a reference: Application to MRI global shimming

Authors

  • Wentao Liu,

    1. Beijing City Key Laboratory for Medical Physics and Engineering, School of Physics, Peking University, Beijing, China
    2. MRI Research Center, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
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  • Xin Tang,

    1. Beijing City Key Laboratory for Medical Physics and Engineering, School of Physics, Peking University, Beijing, China
    2. MRI Research Center, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
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  • Yajun Ma,

    1. Beijing City Key Laboratory for Medical Physics and Engineering, School of Physics, Peking University, Beijing, China
    2. MRI Research Center, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
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  • Jia-Hong Gao

    Corresponding author
    1. Beijing City Key Laboratory for Medical Physics and Engineering, School of Physics, Peking University, Beijing, China
    2. MRI Research Center, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
    3. Brain Research Imaging Center and Department of Radiology, The University of Chicago, Chicago, Illinois, USA
    • Brain Research Imaging Center, The University of Chicago, 5841 South Maryland, MC 2026, Chicago, IL 60637
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Abstract

MRI phase data often suffers from phase wrapping (i.e., phase may be discontinuous by 2π jumps). Numerous MRI phase unwrapping strategies were developed in the past using a criterion based on phase information of local or neighboring voxels. In this study, an alternative and novel three dimensional phase unwrapping strategy is introduced. This method considers the global character of the phase distribution and utilizes continuous trigonometric functions to construct an expected phase map as an unwrapping reference, which is then used to guide the phase correction of every individual voxel. The original phase is estimated by analyzing the derivative of the wrapped phase image. Simulations of various phase wrapped situations were performed and this new method was also used for an in vivo application (i.e., MRI automatic global shimming). Both simulated and experimental results demonstrate that our proposed method is more reliable and robust than traditional algorithms at obtaining correct phase maps, especially in regions of low-signal and air cavities, such as the abdomen and pelvis. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.

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