TRADITIONAL POSTER - ismrm

Poster Sessions
images using spatially dependent filters and omission of background voxels from the filtering calculations. The method is shown to successfully reveal
structural detail in the cortical surface that is otherwise obscured in traditional filtering methods.
3095. Correction of RF Inhomogeneities in FLASH-Based T1 Mapping Using Unified Segmentation
Nikolaus Weiskopf 1 , Antoine Lutti 1 , Gunther Helms 2 , John Ashburner 1 , Chloe Hutton 1
1 Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London, United Kingdom; 2 MR-
Research in Neurology and Psychiatry, University Medical Center, Göttingen, Germany
Quantitative T1 mapping based on variable flip angle acquisitions requires precise knowledge of the local flip angle and is therefore usually combined with
RF transmit mapping methods. RF transmit mapping is not readily available and requires extra scan time. We propose a method to correct for RF
inhomogeneities that does not require measured RF maps. The method uses the unified segmentation and bias correction approach implemented in SPM8 to
simultaneously estimate and correct for the RF inhomogeneities from the T1 maps. The model-based approach is shown to reduce the bias in T1 maps by
more than 50%.
3096. Improved Contrast and Image Homogeneity with BIR4 Pulses in Magnetization Prepared Flair at 7
Tesla
Jaco J.M. Zwanenburg 1 , Fredy Visser, 12 , Vincent O. Boer 1 , Wybe JM van der Kemp 1 , Dennis W. Klomp 1 ,
Peter R. Luijten 1
1 Radiology, University Medical Center Utrecht, Utrecht, Netherlands; 2 Philips Healthcare, Best, Netherlands
It is shown that using BIR4 pulses for excitation and magnetization prepared inversion, can considerably improve the image homogeneity and contrast of
FLAIR images at 7 Tesla, in areas with inhomogeneous B1+ fields.
3097. Distance Weighted B1 Uniformity Correction for Multiple Channel Image Reconstruction
Fred J. Frigo 1,2 , Brian W. Thomsen 1,2 , Joshua V. Marso 1,2 , Jason M. Darby 1,2 , Stephen A. Verdi 1,2 , Chad A.
Rowland 1,2
1 GE Healthcare, Waukesha, WI, United States; 2 Marquette University, Milwaukee, WI, United States
Conventional multiple channel image reconstruction benefits from increased signal-to-noise ratios however hyper-intensity near coil elements can lead to
difficulties in the evaluation of images. We present a novel approach for multiple-channel magnetic resonance image reconstruction with pixel intensity
corrections for B1 non-uniformity. Coil sensitivity maps are generated from the actual data acquired during a scan, so this is a self-referencing technique.
The coil sensitivity maps for each channel are generated based on the Euclidean distance of pixels from each individual coil image to the coil elements.
3098. Non Uniformity Correction Using Cosine Functions and Total Variation Constraint in Musculoskeletal
Nmr Imaging
Noura Azzabou 1,2 , Paulo Loureiro de Sousa 1,2 , Pierre G. Carlier 1,2
1 NMR Laboratory, Institute of Myology, Paris, France; 2 NMR Laboratory, CEA, I2BM, MIRCen, IdM, Paris, France
We introduced here a new technique for non homogeneity correction that does not rely on prior knowledge about all the tissues in the image. To estimate the
non uniformity field, we assumed that it can be modelled as a finite sum of cosine functions. To compute the parameters of the model, we minimised the
variance of the image in the subcutaneous fat region under the constraint that the total variation of the field is minimum. The later constraint is the main
contribution of this paper. Experimental results, on phantom, healthy subjects and pathological cases showed the efficiency of our model.
3099. Phase Correction in Bipolar Multi-Echo Water-Fat Separation for Off-Isocenter Imaging
Hojin Kim 1,2 , Kyung Sung 1 , Misung Han 1,2 , Marcus Alley 1 , Wenmiao Lu 3 , Brian Andrew Hargreaves 1
1 Department of Radiology, Stanford University, Stanford, CA, United States; 2 Department of Electrical Engineering, Stanford
University, Stanford, CA, United States; 3 School of Electrical and Electronic Engineering, Nanyang Technological University,
Singapore
Bipolar multi-echo sequence benefits from reducing scan time as well as motion artifacts at the cost of several sources of phase discrepancy due to the
polarity reversal in the readout gradient. To address phase correction in bipolar sequences, this work proposes the use of simple reference scan with baseline
projections, which corrects linear and constant phase errors. Significantly, this proposed method is applied for off-isocenter imaging, so that accurate waterfat
separation in bipolar sequence is capable at any scan location.
Correcting Hardware Imperfections
Hall B Thursday 13:30-15:30
3100. An Efficient Correction Technique for Constant, Linear and ‘Oblique’ Phase Errors in EPI-
PROPELLER
Novena Rangwala 1,2 , Xiaohong Joe Zhou 1,3
1 Center for Magnetic Resonance Research, University of Illinois Medical Center, Chicago, IL, United States; 2 Department of
Bioengineering, University of Illinois at Chicago, Chicago, IL, United States; 3 Departments of Radiology, Neurosurgery and
Bioengineering, University of Illinois Medical Center, Chicago, IL, United States
A new technique for phase correction of individual blades for EPI-PROPELLER sequences is proposed. Constant, linear, and ‘oblique’ phase corrections
are performed by synthesizing the reference scans for arbitrary blade orientations, using only two reference scans acquired in orthogonal directions. This