TRADITIONAL POSTER - ismrm

2938. A Positive Contrast Method for MR-Lymphography Using Superparamagnetic Iron Oxide
Nanoparticles
Haitao Zhu 1 , Kazuyuki Demachi 1
1 Department of Nuclear Engineering, The University of Tokyo, Tokyo, Japan
Poster Sessions
The objective of this work is to apply a post-processing method in MR-lymphography with superparamagnetic iron oxide nanoparticle (SPION)
enhancement to achieve positive contrast in the image. The method analyzes the echo position shift caused by susceptibility gradient and uses this criterion
to enhance region with large gradient caused by SPIONs. Both phantom and animal experiments are performed to test the method. Results show that this
positive contrast method can generate enhanced signal at the region targeted by SPIONs and might provide additional information in MR-lymphography.
2939. Reconstruction Method for Non-Homogeneous Magnetic Fields Using the Fractional Fourier
Transform
Vicente Parot 1,2 , Carlos Sing-Long 1,2 , Carlos Lizama 3 , Sergio Uribe, 2,4 , Cristian Tejos 1,2 , Pablo
Irarrazaval 1,2
1 Department of Electrical Engineering, Pontificia Universidad Catolica de Chile, Santiago, Chile; 2 Biomedical Imaging Center,
Pontificia Universidad Catolica de Chile, Santiago, Chile; 3 Department of Mathematics and Computer Science, Universidad de
Santiago de Chile, Santiago, Chile; 4 Department of Radiology, Pontificia Universidad Catolica de Chile, Santiago, Chile
In Magnetic Resonance Imaging (MRI) field inhomogeneities produce severe distortions, especially with long acquisition sequences, e.g. EPI. Shimming or
post-processing strategies are usually applied to correct those distortions. However, those approaches require additional hardware or long processing times.
We propose an alternative reconstruction method based on the Fractional Fourier Transform (FrFT) assuming spatially-varying quadratic fields. We tested
our method in phantoms and in vivo acquisitions. Results demonstrate the ability of our reconstruction scheme to correct the geometric distortions that
appear in standard Fourier Transform reconstructions under non homogeneous fields.
2940. Geometrically Accurate Positive Contrast of Field Disturbances Using RAdial Sampling with Off-
Resonance Reconstruction (RASOR).
Hendrik de Leeuw 1 , Peter R. Seevinck 1 , Clemens Bos 2 , Gerrit H. van de Maat 1 , Chris J.G. Bakker 1
1 Image Sciences Institute, Utrecht, Netherlands; 2 Philips healthcare
With the advent of short-TE acquisitions, such as UTE and SWIFT, center out radial acquisition schemes to fill k-space are gaining interest. Although these
short TE acquisitions minimize signal dephasing, they still suffer from field inhomogeneities in terms of geometric distortion. Still geometrically accurate
depiction and localization of local field disturbers can be achieved by a 3D center-out radial acquisition by using off-resonance acquisition or reconstruction
(RASOR). The advantage of RASOR reconstruction is a more precise determination of shape and location of the field disturbance, while retaining the
original image.
2941. Spiral Off-Resonance Distortion Correction for Tagged MRI Using Spectral Peak Matching and
HARP Refinement
Harsh K. Agarwal 1 , Xiaofeng Liu 1 , Khaled Z. Abd-Elmoniem 2 , Jerry L. Prince 1
1 Department of Electrical and Computer Engineering, The Johns Hopkins University, Baltimore, MD, United States; 2 National
Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
Off-resonance due to magnetic field inhomogeneity causes geometric distortion in tagged images acquired using a segmented spiral k-space data acquisition.
This causes erroneous alignment of horizontal and vertical tag acquisitions and inaccurate displacement estimation. A technique based on fast marching
HARP refinement is proposed to estimate and correct for the distortion. Improved motion estimation is demonstrated on an in vivo data set.
2942. Multi-GPU Implementation for Iterative MR Image Reconstruction with Field Correction
Yue Zhuo 1 , Xiao-Long Wu 2 , Justin P. Haldar 2 , Wen-mei W. Hwu 2 , Zhi-Pei Liang 2 , Bradley P. Sutton 1
1 Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States; 2 Electrical and Computer Engineering,
University of Illinois at Urbana-Champaign, Urbana, IL, United States
Nowadays Graphics Processing Units (GPU) leads high computation performance in science and engineering application. We propose a multi-GPU
implementation for iterative MR image reconstruction with magnetic field inhomogeneity compensation. The imaging model includes the physics of field
inhomogeneity map and its gradients, and thus can compensate for both geometric distortion and signal loss. The iterative reconstruction algorithm is
realized on C-language based on Compute Unified Device Architecture (CUDA). Result shows the performance of multi-GPU gains significant speedup by
two orders of magnitude. Therefore, the fast implementation make the clinical and cognitive science requirements are achievable for accurate MRI
reconstruction.
2943. Fiber Orientation Dependance of T2* Relaxation Time in the Whole Human Brain at 3T
Benjamin Bender 1 , Uwe Klose 1
1 University Hospital Tübingen, Department of Diagnostic and Interventional Neuroradiology, Tübingen, Germany
Recent publications suggest a relationship between white matter fiber orientation and T2* contrast at higher field strengths. In this study the relationship
between fiber orientation and B0 for normal and tilted head position was examined in the whole human brain at 3T. As previously shown by Wiggins et al.
for the cingulum and corpus callosum, WM signal intensity in the whole brain changed when the head was tilted. Blood vessels following the fiber tracts
could explain the relationship found between B0 and relaxation rate, while a magic angle effect cannot explain the measured relationship.