TRADITIONAL POSTER - ismrm

Poster Sessions
2932. Subtraction in View-Shared 3D Contrast-Enhanced MRA
Eric Allen Borisch 1 , Clifton R. Haider 1 , Roger C. Grimm 1 , Stephen J. Riederer 1
1 Radiology, Mayo Clinic, Rochester, MN, United States
3D contrast-enhanced MR Angiography frequently uses a pre-contrast (tissue) acquisition as a subtraction reference (mask) to improve the output image
quality and contrast-to-noise ratio. We discuss the appropriate application of this technique to the case of 3D time-resolved view-shared reconstructions,
including at what stage in the reconstruction process the subtraction is performed and the selection of effective mask data to suppress magnetization history
effects.
2933. On Temporal Filtering Effects Caused by the Subtraction of Temporal Average in Dynamic Parallel
MRI
Irene Paola Ponce 1 , Martin Blaimer 2 , Felix Breuer 2 , Peter Michael Jakob 1,2 , Mark A. Griswold 3 , Peter
Kellman 4
1 Experimental Physics 5, University of Würzburg, Würzburg, Bavaria, Germany; 2 Research Center Magnetic Resonance Bavaria
(MRB), Würzburg, Bavaria, Germany; 3 Department of Radiology, University Hospitals of Cleveland and Case Western Reserve
University, Cleveland, OH, United States; 4 Laboratory of Cardiac Energetics, National Institutes of Health, National Heart, Lung and
Blood Institute, Bethesda, MD, United States
Many of Parallel MRI techniques are based on a time-interleaved acquisition scheme and allow dynamic imaging with high frame rates. In addition, in order
to improve the SNR, the temporal average (also referred to as direct current, DC) is subtracted from the raw data so that only the dynamics of the object is
reconstructed. In this work we demonstrate that DC subtraction may lead to temporal filtering effects in form of signal nulls in the temporal frequency
spectra of the reconstructed images. We propose to correct the DC by an additional GRAPPA reconstruction prior to subtraction from the raw data.
2934. A Dynamic-Phase Extension for Model-Based Reconstruction of Breast Tumor Dynamic Contrast
Enhanced MRI
Benjamin K. Felsted 1 , Ross T. Whitaker 1 , Matthias C. Schabel 2 , Edward V.R. DiBella 2
1 School of Computing, University of Utah, Salt Lake City, UT, United States; 2 Department of Radiology, University of Utah, Salt
Lake City, UT, United States
Introduction: We extend the model-based reconstruction method with a physically based linear-phase model that can account for gadolinium field
distortions. Methods: Both constant- and linear-phase models were used in reconstructing two 4D breast DCE k-space acquisitions, retrospectively
undersampled at R-factors of 1, 4, and 8. Results: Image reconstruction errors correlate spatially with dynamic image phase estimation errors. The errors of
the constant-phase model grow fastest as R increases. Conclusion: The new extension can reduce most of the error from phase. The reconstructions have
full spatial resolution without the blurring, ghosting, and ringing spatial artifacts typically associated with aggressive undersampling.
2935. Estimation of Superresolution Performance
Gerrit Schultz 1 , Maxim Zaitsev 1
1 Diagnostic Radiology - Medical Physics, University Hospital Freiburg, Freiburg, Germany
In this contribution a method for the estimation of Superresolution performance is presented. For adequately designed reconstruction methods, the
modulations of the rf coil sensitivities can be used to extend the acquired gradient-encoded k-space region. This extension directly results in a resolution
improvement. The k-space representation of the sensitivity maps gives a global estimate about the degree of this k-space extension. Resolution is
investigated by performing a point spread function analysis. Simulated data are presented and verified with measurement results based on a standard 2D-CSI
sequence.
2936. FREBAS Domain Super-Resolution Reconstruction of MR Images
Satoshi Ito 1 , Yoshifumi Yamada 1
1 Research Division of Intelligence and Information Sciences, Utsunomiya University, Utsunomiya, Tochigi, Japan
Super-resolution is a method of generating images beyond the limit of the resolution. Recently, a method by which to realize super-resolution by a technique
that performs registration by a sub-pixel unit from several pieces of an image has been reported. Gerchberg-Papoulis (GP) method is known to realize superresolution
from a single image and signal, however, spatial resolution will not be improved well when it is based on the Fourier transform. On the other
hand, GP method involving convolution integral can expand the signal band easily and the resultant image has higher resolution. In this study, we
investigated the super-resolution of images using FREBAS transform that can be considered as a kind of multi-resolution image analysis based on
convolution integral. Improvement of resolution on the image space with reference to the scaling parameter of FREBAS transform is examined.
2937. Seed Localization in MRI-Guided Prostate Brachytherapy Using Inversion-Recovery with ON-
Resonant Water Suppression (IRON)
Nathanael Kuo 1 , Junghoon Lee 1 , Clare Tempany 2 , Matthias Stuber 1 , Jerry Prince 1
1 Johns Hopkins University, Baltimore, MD, United States; 2 Brigham and Women's Hospital, Boston, MA, United States
An MRI pulse sequence and a corresponding image processing algorithm to localize prostate brachytherapy seeds during or after therapy are presented.
Inversion-Recovery with ON-resonant water suppression (IRON) is an MRI methodology that generates positive contrast in regions of magnetic field
susceptibility, as created by brachytherapy seeds. Phantoms comprising of several materials found in seeds were created to assess the usability of IRON for
imaging seeds. Resulting images show that seed materials are clearly visible with high contrast using IRON. A seed localization algorithm to process IRON
images demonstrates the potential of this imaging technique for seed localization and dosimetry.