ELECTRONIC POSTER - ismrm

14:30 5053. Improvement of the Arterial Input Function Considering B 1 -Inhomogeneities
Robert Merwa 1 , Karin Kapp 2 , Franz Ebner 3 , Thorsten Feiweier 4 , Gernot Reishofer 3 ,
Rudolf Stollberger 5
1 Medical Engineering, FH OÖ - Upper Austria University of Applied Sciences, Linz, Austria; 2 Department of
Radiation Therapy, Medical University of Graz, Graz, Austria; 3 Department of Radiology, Medical University
of Graz, Graz, Austria; 4 Healthcare, Siemens AG, Germany; 5 Institute of Medical Engineering, Graz University
of Technology, Graz, Austria
DCE MRI was performed at 3 T in combination with a special sequence in order to determine B 1 inhomogenities. AIF and tissue
concentrations were calculated and the kinetic parameters K trans and V e were determined with a generalized kinetic model. The
absolute deviation of the maximum value of two comparable AIFs can be improved by a factor up to 70 and the root mean square
deviation concerning the two AIFs can be decreased by a factor up to 30 if B 1 inhomogeneities are corrected. Also the deviations of
Ktrans and Ve in respect of the two AIFs are significantly lower.
15:00 5054. Stent Imaging Using Metal Artifact Reduction Sequence
Sang-Young Zho 1 , Min Oh Ghim 1 , Dong Joon Kim 2 , Dong-Hyun Kim 1,2
1 Electrical and Electronic Engineering, Yonsei University, Seoul, Korea, Republic of; 2 Radiology, Yonsei
University College of Medicine, Seoul, Korea, Republic of
We examine a method for high-resolution stent imaging using metal artifact correction sequence and parallel imaging technique.
EPI Correction
Hall B Monday 14:00-16:00 Computer 123
14:00 5055. Robust Elimination of EPI Nyquist Ghosts Via Spatial and Temporal Encoding
W Scott Hoge 1 , Huan Tan 2 , Robert A. Kraft 2
1 Radiology, Brigham and Women's Hospital, Boston, MA, United States; 2 Virgina-Tech Wake Forest School of
Biomedical Engineering, Winston-Salem, NC, United States
Nyquist ghosts are an inherent artifact in EPI acquisitions. We propose here a method that fuses ghost correctuion methods based on
spatial encoding (via multiple coils) and temporal encoding (via cyclic variations in the acquisition sequence). Post acquisition,
PLACE is employed to cancel ghosting artifacts in data used to estimate self-referenced parallel MR imaging reconstruction
coefficients. The improved pMRI reconstruction coefficients are then employed on each frame, to reconstruct a ghost free image. We
demonstrate that this self-referenced approach significantly reduces Nyquist ghosts, and is robust to temporal variations such as
magnetic field drift with minimal latency.
14:30 5056. Optimized Acquisition Strategy for Reference-Free Reduction of Nyquist Ghosting
in EPI at 7 T
Benedikt A. Poser 1,2 , Pål Erik Goa, 1,3 , Markus Barth, 1,2
1 Erwin L Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany;
2 Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands;
3 Department of Medical Imaging, St. Olavs University Hospital, Trondheim, Norway
Nyquist (N/2) ghosting in EPI tends to become particularly problematic at ultra-high field. Strongly dependent on imaging parameters
–especially echo spacing and readout bandwidth– ghosting may pose considerable practical limitations when setting up fMRI
protocols at 7 T and above.
We here show that residual ghosting is caused by an often appreciable mismatch between phase correction and imaging data. We
propose a small but powerful sequence modification, namely an optimized timing of the phase-correction navigators, to overcome this
problem and thereby remove the practical restrictions due to ghosting. Phantom and in vivo results demonstrate ghost reductions by up
to factor four.
15:00 5057. Robust Method for EPI Ghost Correction
Frank Godenschweger 1 , Myung-Ho In 1 , Oliver Speck 1
1 Biomedical Magnetic Resonance, Institute for Experimental Physics, Otto-von-Guericke University,
Magdeburg, Germany
A Nyquist ghost correction of EPI is propose, which determines the phase correction differences between channels and slices with
high accuracy in a preparation step from a set of navigator echoes. Taking this calibration into account, only one single correction
needs to be determined dynamically for all slices and channels during the EPI series, greatly improving stability.
The robustness of the proposed technique was tested on phantom and in-vivo data. The proposed technique for EPI ghost correction
dramatically improves the image quality.