ELECTRONIC POSTER - ismrm

Thursday 13:30-15:30 Computer 95
13:30 4626. Self-Referenced Flip Angle Mapping for Hyperpolarized Gas MRI
Eric Frederick 1,2 , Mirko Hrovat 3 , Samuel Patz 2
1 Applied Physics, University of Massachusetts in Lowell, Lowell, MA, United States; 2 Radiology, Brigham and
Women's Hospital, Boston, MA, United States; 3 Mirtech Inc, Brockton, MA, United States
Hyperpolarized noble gas imaging is a non-equilibrium imaging method where gas magnetization is depleted by RF excitations. Due
to B_1 field inhomogeneities, this depolarization may not be uniform and therefore a B_1 flip angle map is required to correct the
images. This process is typically performed by acquiring an additional set of images. We propose an alternative method where the flip
angle map is obtained from one set of images. To do this, we break up a fully sampled image into two undersampled images that are
then used for B_1 flip angle mapping. We demonstrate these methods with simulations.
14:00 4627. Towards a Better Understanding of Helium-3 MRI Manual Segmentation Error
Using Fuzzy C-Mean Methods
Mohammadreza Heydarian 1 , Andrew Wheatley 1 , Grace Parraga 1,2
1 Robarts research Institute, London, Ontario, Canada; 2 Medical Biophysics, University of Western Ontario,
London, On, Canada
Hyperpolarized helium-3 MRI provides a way to visualize and quantify lung function based on segmentation of helium-3 ventilation
images. Manual segmentation of 3He ventilation volumes is time consuming and prone to observer error. To address this limitation,
we developed and applied a fully automated fuzzy c-mean (FCM) method for segmenting ventilated regions and observed significant
associations between the automated and manual segmentation methods. FCM provides a fully automated, robust and efficient method
for segmenting ventilated regions of hyperpolarized helium-3 images.
14:30 4628. Optimisation of Velocity Encoding Gradients for Phase Contrast Gas Velocity
Taking Diffusion Into Account.
Lionel Martin 1 , Xavier Maître 1 , Mathieu Sarracanie 1 , Marlies Friese 2 , Ludovic de
Rochefort 1 , Rose-Marie Dubuisson 1 , Emeline Boriasse 1 , Emmanuel Durand 1
1 Imagerie par Résonance Magnétique Médicale et MultiModalités (UMR8081), Univ Paris-Sud, CNRS, Orsay,
France; 2 Center for Magnetic Resonance, The University of Queensland, Brisbane, Queensland, Australia
MR flow measurement techniques have mostly been used in liquids. For coherent motion (flow), bipolar gradients induce a phase shift
and a signal drop for incoherent motion (diffusion). This effect, negligible for liquids, cannot be neglected for gases. Competition
between these two phenomena results in the existence of an optimal FOS that could be theoretically determined. 2D velocity maps of
parabolic flows were acquired with different FOS and gases. Results show that velocity error is a function of the FOS and a different
optimal FOS is reached for each gas. Thus, they validate our theoretical simulations.
15:00 4629. Hyperpolarized 83Kr MR Relaxation Measurements in Excised Rat Lungs.
Karl F. Stupic 1 , Nancy D. Elkins 2 , Galina E. Pavlovskaya 3 , John E. Repine 2 , Thomas
Meersmann, 1,3
1 Department of Chemistry, Colorado State University, Fort Collins, CO, United States; 2 Health Science Center,
Webb-Waring Institute, University of Colorado, Denver, CO, United States; 3 School of Medicine, University of
Nottingham, Nottingham, United Kingdom
Hyperpolarized (hp) 83Kr has been previously shown to provide T1 relaxation weighted MRI contrast that is highly sensitive to the
surface chemistry in low surface-to-volume model surface systems In the present work 83Kr T1 relaxation in excised rat lungs is
investigated as a function of lung inflation. Surprisingly, the relaxation in ex vivo lungs does not change with increased lung inflation
(when the effects of airways are eliminated) despite the presumably changing surface to volume ratios in the alveoli. The measured
relaxation times are long enough to permit future in vivo studies.
Metabolism Liver & Other I
Hall B Monday 14:00-16:00 Computer 96
14:00 4630. Reproducibility of MRI-Determined Proton Density Fat Fraction (PDFF) Across
MR Scanner Platforms and Field Strength
Geraldine Hye Won Kang 1 , Michael Schroeder 1 , Masoud Shiehmorteza 1 , Benjamin
Johnson 1 , Tanya Wolfson 1 , Anthony Gamst 1 , Gavin Hamilton 1 , Mark Bydder 1 , Takeshi
Yokoo 1 , Claude Sirlin 1
1 Radiology, University of California, San Diego, San Diego, CA, United States
As a result of the growing epidemic of obesity, fatty liver disease has become the most common liver condition in the United States.
Thus, there is an increasing need for a noninvasive fat quantification technique. We have developed a T1-independent, T2*-corrected,
spectral modeled chemical shift based fat quantification technique, which permits estimation of the proton density fat fraction (PDFF).
Here we show that PDFF measured by this technique is reproducible across field strength and vendor and has high accurt5acy using
spectroscopy as the reference.