Se-Hong Oh1, Jun-Young Chung1,
Myung-Ho In2, Maxim Zaitsev3, Oliver Speck2,
Young-Bo Kim1, Zang-Hee Cho1
1Neuroscience Research Institute,
Gachon University of Medicine and Science, Incheon, Korea, Republic of; 2Department
of Biomedical Magnetic Resonance, Institute for Experimental Physics,
Otto-von-Guericke University Magdeburg, Magdeburg, Germany; 3Department
of Radiologic Research, Medical Physics, University Hospital of Freiburg,
Freiburg, Germany
Echo-planar
imaging (EPI) is one of the fastest and most widely used MRI pulse sequences
in the field of MRI. Compared to conventional imaging sequence, EPI is more
prone to a variety of artifacts. A prominent EPI artifact is geometric
distortion due to strong magnetic field inhomogeneity and susceptibility.
Previous PSF mapping method, which was implemented by Zaitsev et al. used GE
(Gradient Echo) StdDev (standard deviation) image as a base and produced a
mask to extrapolate pixel shift map. Flow artifact as well as setting of
the parameters (i.e. threshold value) can affect the result of mask. And the
extrapolated shift map which resulting shift maps with extrapolation
eventually have error. Consequently corrected images will also have errors
induced by mask errors and flow artifacts. So we propose new mask calculation
method based on using a 2D PSF data based, not based on the GE StdDev image
as previously used. This method is capable of making automatic mask
calculation procedure, along with the advantage of eliminating flow induced
ghost artifact all together.
Keywords