TRADITIONAL POSTER - ismrm

Poster Sessions
3008. Computer Simulations of 3D MPRAGE in Human Brain with Inclusion of Inadvertent Magnetization
Transfer Effects
Gerald Matson 1 , Hui Liu 1
1 CIND, Veterans Affairs Medical Center, San Francisco, CA, United States
Magnetization transfer (MT) effects in the human brain occur when there is magnetization transfer between the free and bound water pools associated with
gray and white matter. These MT effects can become significant, particular when longer excite pulses are used, for example, to induce uniform tip angles in
the presence of non-uniform RF fields. Therefore, we developed a simulation program written in Matlab to calculate these MT effects, and to simulate the
3D MPRAGE experiment. The simulations show that the MT effects must be taken into account when longer excite pulses are used in the 3D MPRAGE
experiment.
7T MRI
Thursday 13:30-15:30
3009. High Resolution Whole Head 3D Susceptibility Mapping at 7T: A Comparison of Multi-Orientation
and Single Orientation Methods
Samuel James Wharton 1 , Richard Bowtell 1
1 Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom
Phase images generated using gradient echo techniques at high field show excellent contrast related to variation of magnetic susceptibility across brain
tissues. Calculating susceptibility maps from phase data is made difficult by the ill-posed nature of the deconvolution problem which must be solved. Careful
conditioning is therefore required. Here, we compare the performance of three conditioning strategies ((i) combination of data acquired at multiple
orientations; (ii) k-space thresholding of data acquired at a single orientation; (iii) incorporation of structural information using corresponding modulus data)
in the calculation of susceptibility maps from high-resolution phase images of the brain and a phantom.
3010. Basis for Contrast Enhanced T 1 - Weighted Imaging Using SE at High Field
Niravkumar Darji 1 , Michel Ramm 1 , Oliver Speck 1
1 Department Biomedical Magnetic Resonance, Institute for Experimental Physics, Otto-von-Guericke University Magdeburg,
Magdeburg, Germany
Aim of this study was to reduce fat signal without using fat saturation pulse. This task was achieved by modification of RF pulse in SE sequence. Different
bandwidth of the refocusing pulse allows suppression of fat signal without increased SAR in high resolution SE imaging. The reduced fat signal with longer
refocusing pulse duration is evident from in-vivo experiments.
3011. Adiabatic Magnetization Preparation Pulse for T 2 -Contrast at 7 Tesla
Priti Balchandani 1 , Daniel Spielman 1
1 Radiology, Stanford University, Stanford, CA, United States
T 2 -weighted sequences such as Fast Spin Echo are highly susceptible to the B 1 -inhomogeneity and are SAR-intensive at 7T. We present an alternative
method to obtain T 2 -contrast at 7T which utilizes an adiabatic magnetization preparation (AMP) pulse. The AMP pulse is a 0° BIR-4 pulse with delays
inserted between segments to introduce T 2 -decay. Phantom and in vivo experiments show that the AMP pulse provides more uniform SNR and T 2 -contrast
over the excited slice. The AMP pulse is suitable for use in a volumetric fast gradient echo sequence.
3012. Comparison of Reduced FOV Techniques for High Resolution Imaging at 7T
Christopher Joseph Wargo 1 , Marcin Jankiewicz 1 , John C. Gore 1
1 Vanderbilt University Institute of Imaging Science, Nashville, TN, United States
High-resolution MR imaging benefits from ultra-high field strength such as at 7T due to improvement in signal, but requires acquisition of a large number of
voxels. This increases the scan duration, and thus field and time dependent artifacts, and reduces temporal resolution for functional studies. Reduction of
the FOV enables scan times to be shortened, but introduces tradeoffs between SNR, scan efficiency, SAR, and image artifacts. In this abstract, we compare
a subset of selective excitation approaches including STEAM, PRESS, OVS, and spectral spatial pulses, for reduced-FOV resolution improvement in
phantoms using a human 7T system.
3013. Towards the Accurate and Precise Assessment of SNR in Vivo at 7T
Josef Habib 1,2 , Dorothee P. Auer 1 , Richard W. Bowtell 2
1 Academic Radiology, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom; 2 Sir Peter Mansfield Magnetic
Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
The Signal-to-Noise ratio (SNR) is a fundamental and critical data quality measure in MRI, with several investigations dedicated to devising and validating
optimized measurement techniques. While the introduction of higher field strength MRI systems is expected to impact attainable SNR levels, this study
shows that the prevalent technique for measuring SNR in vivo performs sub-optimally at 7 Tesla, due to artifacts presumably caused by the increased
sensitivity to subject or physiological motion. Here we propose the use of an alternative measurement technique for increased robustness, after quantitatively
evaluating its precision and accuracy.