TRADITIONAL POSTER - ismrm

Poster Sessions
3061. 4D MAP Image Reconstruction of MRI Data
Jacob Hinkle 1 , Ganesh Adluru 2 , Edward DiBella 2 , Sarang Joshi 1
1 Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT, United States; 2 Utah Center for Advanced
Imaging Research, University of Utah, Salt Lake City, UT, United States
Conventional MRI reconstruction techniques are susceptible to artifacts when imaging moving organs. In this paper, a reconstruction algorithm is developed
that accommodates motion instead of altering the scanning protocol. The maximum a posteriori (MAP) algorithm uses the raw time-stamped data to
reconstruct the images and estimate deformations in anatomy simultaneously. The algorithm eliminates artifacts by avoiding gating processes and increases
signal-to-noise ratio (SNR) by using all of the collected data. The algorithm is tested in a simulated torso phantom and is shown to increase image quality by
dramatically reducing motion artifacts.
3062. Impact of Mechanical Vibration During DWI on Diffusion Parameter Estimation in Human Kidneys
Peter Vermathen 1 , Tobias Binser 1 , Chris Boesch 1
1 Dept. Clinical Research, University Bern, Bern, Switzerland
DWI leads to patient table vibration that may affect image quality, as has been demonstrated previously in phantoms and brain. We therefore investigated the
impact of mechanical vibration during abdominal DWI on diffusion parameter estimation. Diffusion scans were performed on three subjects that were once
in direct contact with the MR-system, thus experiencing vibration, and once without contact to the MR-System. The results demonstrate that the impact of
vibration on diffusion parameter estimation, including micro-perfusion estimation, and also on the image intensity is only small. This holds true for standard
measurement parameters.
3063. On the Application of TGRAPPA in Functional MRI
Hu Cheng 1
1 Indiana University, Bloomington, IN, United States
GRAPPA has been widely used in fMRI recently to improve spatial resolution. A drawback of GRAPPA for fMRI is that head motion in the reference scans
can result in significant artifact for all the images in a run and higher temporal noise level. This problem can be solved by TGRAPPA using time interleaved
sampling scheme. Separate reconstruction is needed for the interleaved k-space to minimize signal variation from volume to volume caused by phase errors.
Although TGRAPPA has less statistical power than GRAPPA, the ability of retrospective motion correction makes it appealing in some application.
3064. Necessity of Sensitivity Profile Correction in Retrospective Motion Correction
Chaiya Luengviriya 1,2 , Jian Yun 1 , Kuan Lee 3 , Julian Maclaren 3 , Oliver Speck 1
1 Department of Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany; 2 Department of Physics,
Kasetsart University, Bangkok, Thailand; 3 Department of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany
Image artifacts induced by subject motion during multi-channel MRI were simulated for different sensitivity map profiles and different amounts of abrupt
random motion. More localized maps resulted in stronger artifacts in the images. Two procedures for retrospective motion correction, k-space signal
correction and sensitivity map correction were applied during an iterative non-Cartesian SENSE reconstruction. The signal correction evidently reduced the
artifacts. The sensitivity map correction further improved image quality for strong motion and highly localized maps, at the cost of a longer computation
time. For small motion and less localized maps, sensitivity map correction can be avoided since no improvement was visible.
3065. Dynamic Imaging Motion Artifact Reduction Using Adaptive K-Space Polynomial Interpolation
Travis B. Smith 1 , Krishna S. Nayak 1
1 Electrical Engineering, University of Southern California, Los Angeles, CA, United States
Any object movement during or between MRI acquisition readouts leads to data inconsistency artifacts in the images. The manifestation of these artifacts
depends on the k-space sampling trajectory. For example, in echo-planar imaging they appear as “ghosting” artifacts, and in spiral imaging they manifest as
“swirling” artifacts. Dynamic imaging, which attempts to capture body or physiological motion through continuous acquisitions, is vulnerable to these
artifacts. In this work, we present an adaptive polynomial interpolation algorithm to reduce these artifacts without introducing significant motion blurring.
In-vivo results are presented to compare the algorithm with other motion artifact reduction techniques.
3066. Magnitude-Weighted Phase Based Edge Detection for Navigator Gated Imaging
Kenichi Kanda 1 , Yuji Iwadate 2 , Yoshikazu Ikezaki 1
1 MR Engineering, GE Healthcare Japan, Hino, Tokyo, Japan; 2 MR Applied Science Laboratory, GE Healthcare Japan, Hino, Tokyo
In navigator echo technique, accurate position detection of the diaphragm is essential. The edge detection analysis based on the phase profile of navigator
enables the navigator gated imaging even with the saturation effect. However, the phase profile is sometimes unstable in the lung, and wrong position can be
detected accordingly. We present a hybrid algorithm utilizing both magnitude and phase information to detect the diaphragm position. Our results show that
the edge detection based on the magnitude-weighted phase data can detect the diaphragm position accurately even when the data have a fuzzy magnitude
edge or noisy phase in the lung.
3067. Irretrievable Signal Loss in Partial-Fourier Acquired Diffusion-Weighted Images
Marcel Peter Zwiers 1 , Eelke Visser 2 , David Gordon Norris 2 , Nico Papinutto 3 , Benedikt Andreas Poser 2
1 Donders Institute for Brain, Cognition and Behaviour, Nijmegen, -, Netherlands; 2 Donders Institute for Brain, Cognition and
Behaviour, Nijmegen, Netherlands; 3 Center for Mind-Brain Sciences, Trento, Italy
Diffusion weighted (DW) partial-Fourier (PF) imaging is highly sensitive to cardiac activity induced signal voids that depend critically on the image
reconstruction method. The current explanation is that these artefacts result from incorrect phase estimation. We found that artefacts remained present in the
PF acquired images, even when using zero-padding reconstruction or true (ideal) phase information. Cardiac pulsations induce phase gradients that can shift
the local low-frequency information into the unacquired part of k-space. The associated signal voids are therefore irretrievable by any PF reconstruction
method. Thus, PF DW imaging should generally be avoided or used solely with cardiac gating.