MRI Research Today is a free monthly online journal that collates and summarizes the latest research about MRI, including details on magnetic resonance imaging, neuroimaging, brain tumors. | ||||||||
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A modified fourier-based phase unwrapping algorithm with an application to MRI venography.Bagher-Ebadian H, Jiang Q, Ewing JR Department of Neurology, Henry Ford Hospital, Detroit, Michigan, USA. PURPOSE: To present a single-step deterministic procedure for unwrapping MRI phase maps. MATERIALS AND METHODS: Using an algorithm previously developed for optical applications, Laplacian operators were applied in the Fourier space of the MRI phase map. The original Fourier-based phase unwrapping algorithm was modified so that demodulation accomplished the required signal symmetrization in Fourier space. To evaluate the method's performance in the presence of thermal noise, a set of wrapped phase maps were simulated at different levels of noise in k-space, and the response of the algorithm at different levels of signal-to-noise ratio (SNR) was evaluated for stability. To demonstrate its utility in MRI, the algorithm was applied to the wrapped phase maps of susceptibility-weighted imaging (SWI) studies, which were then used to generate venograms. RESULTS: In simulated phase wrapping, the algorithm correctly reproduced the original phase for a wide range of phase gradients and noise. The procedure was fast and produced useful maps of venous structures in SWI images. CONCLUSION: A fast and stable single-step deterministic method for unwrapping MRI phase maps is available for such applications as SWI and mapping of static magnetic field inhomogeneity. J. Magn. Reson. Imaging 2008. (c) 2008 Wiley-Liss, Inc. Published 5 March 2008 in J Magn Reson Imaging, 27(3): 649-52.
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