Parallel Imaging Method for Split-Blade PROPELLER DWI
Donglai Huo1, Zhiqiang Li2, Eric Aboussouan1, John P. Karis3, James G. Pipe1
1Barrow Neurological Institute, Phoenix, Arizona , USA; 2GE Healthcare, Waukesha, Wisconsin, USA; 3Southwest Neuro-Imaging, Phoenix, Arizona , USA
PROPELLER and Turbo-PROP DWI have shown advantages over traditional EPI DWI with high resolution, benign behavior of motion artifacts, and robustness to off-resonance. A split-blade approach is often applied to meet the non-CPMG conditions but makes PROPELLER less robust to motion. In order to widen the PROPELLER blade and reduce motion artifact, we implemented a “Mutual-Calibration” parallel imaging method, in which even and odd echoes are used as calibration data for each other. There is no motion between calibration and reconstruction data, and no additional ACS data are required.
GRAPPA-Accelerated Readout-Segmented EPI for High
Resolution Diffusion Imaging
Samantha J. Holdsworth1, Stefan Skare1, Rexford D. Newbould1, Anders Nordell2, Roland Bammer1
1Stanford University, Palo Alto, California , USA; 2Karolinska University Hospital, Stockholm, Sweden
Readout mosaic segmentation (RS-EPI) has been suggested as an alternative approach to EPI for high resolution diffusion-weighted imaging (DWI) with minimal geometric distortions. In this abstract, peripherally cardiac gated and non-gated RS-EPI-DW images are acquired with the use of parallel imaging. The methods used to phase correct and reconstruct the partial Fourier GRAPPA-accelerated RS-EPI-DW data are described. It is shown that patient handling can be simplified with the use of non-gated acquisitions and minimally-overlapping blinds. The efficient acquisition of high resolution RS-EPI images makes this sampling strategy a useful alternative to other navigated methods used for DW imaging.
High-Resolution Diffusion Tensor Imaging
at 3T with Radial-FSE
Joelle E. Sarlls1, Carlo Pierpaoli1
1National Institutes of Health, Bethesda, Maryland, USA
We developed a diffusion-weighted radial-FSE sequence that is insensitive to magnetic field inhomogeneity that can produce very high-resolution, undistorted images suitable for DTI mapping at 3T. This was accomplished by implementing a combined strategy of a mixed-CPMG phase cycling scheme, to mitigate the violation of the CPMG condition for FSE sequences with a diffusion preparation, and a wider refocusing than excitation slice, to mitigate the lack of B1-homogeneity at higher fields. DTI data acquired with the modified radial-FSE sequence provides undistorted DTI maps, which reveal anatomical details that are currently impossible to image with single-shot EPI.
A Navigated Non-CPMG Turbo Spin Echo Pulse Sequence
for High Resolution Diffusion Imaging
Yongquan Ye1, 2, Yan Zhuo1, 2, Jing An, 23, Xiaohong Joe Zhou4
1Institute of Biophysics, and Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China; 2Beijing MRI Center for Brain Research, Beijing, People's Republic of China; 3Siemens Mindit Magnetic Resonance Ltd, Shenzhen, People's Republic of China; 4Univ. of Illinois Medical Center, Chicago, Illinois, USA
Recent studies have shown that diffusion-weighted multi-shot turbo spin echo (DW-msTSE) sequences can effectively overcome the limitations imposed by single-shot EPI techniques. Two of the major challenges confronting DW-msTSE include (a) motion sensitivity and (b) violation of the CPMG conditions. We have developed a non-CPMG DW-msTSE sequence to address both problems. Motion sensitivity was reduced by a 2D navigator. The issue with CPMG violation was addressed by a variable crusher gradient scheme that eliminated stimulated echoes from the signal pathways. The DW-msTSE sequence has produced high-resolution, artifact-free diffusion images from both phantoms and healthy human volunteers.
High-Resolution Axial DWI of the Spinal Cord with
Reduced-FOV Single-Shot EPI
Emine Ulku Saritas1, Charles H. Cunningham2, Jin Hyung Lee1, Eric T. Han3, Dwight G. Nishimura1
1Stanford University, Stanford, California , USA; 2University of Toronto, Toronto, Canada; 3GE Health Care Global Applied Science Laboratory, Menlo Park, California , USA
Axial in vivo DWI of the spinal cord requires high spatial resolution, due to the small cross-sectional size of the spinal cord. This is very challenging, considering the sources of motion around the spinal cord and the highly inhomogeneous magnetic environment of the spine. Here, we achieve high-resolution axial in vivo ss-DWEPI images by reducing the FOV in the phase-encode direction with a 2D echo-planar RF excitation pulse. This excitation scheme is compatible with multi-slice imaging, and furthermore suppresses the signal from fat with the incorporation of a 180o refocusing pulse.
Parallel Line Scan Diffusion Imaging
Renxin Chu1, Bruno Madore1, Lawrence P. Panych1, Stephan Maier1
1Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
Line scan diffusion imaging (LSDI) allows for considerable robustness against motion without artifacts due to phase wrapping. Combing LSDI and parallel imaging techniques, we propose a novel parallel line scan diffusion imaging (pLSDI) technique with a multiple slice acquisition scheme. The prominent advantage of pLSDI is not only its accelerated acquisitions for LSDI, but the fact that this can be done at essentially no cost in SNR. Phantom and human brain imaging were carried out to test the technique. Our proposed pLSDI approach allows signal separation without phase encoding, while maintaining motion robustness and avoiding additional chemical shift and susceptibility artifacts. The addition of parallel imaging to line-scan imaging accelerates the acquisition with at no losing SNR.
Diffusion at Short Time Scales: Q-Space
Imaging with Chirped Gradient Waveforms
Andrew JM Kiruluta1, 2, Isam Abu Qasmieh3
1Harvard University, Cambridge, Massachusetts, USA; 2Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts, USA; 3university of massachusetts Lowell, Lowell, Massachusetts, USA
The practical limitations imposed by the requirement for delta function type diffusion sensitizing gradients in q-space imaging of diffusing spins, can be relaxed if these impulse gradients are replaced with chirped waveform gradient in a Chirp Gradient Spin Echo (CGSE) experiment. In this abstract, chirped diffusion sensitizing gradients are analytically and through numerical simulations and experiments, shown to yield a practical alternative that asymptotically approaches that using delta functions in a q-space experiment.
Observation of Microscopic Diffusion Anisotropy in
the Spinal Cord Using Double-Pulsed Gradient Spin Echo MRI
Michal E. Komlosh1, Martin J. Lizak2, Ferenc Horkay3, Raisa Z. Freidlin4, Peter J. Basser3
1NICHD,NIH, Bethesda, USA; 2NINDS,NIH, Bethesda, Maryland, USA; 3NICHD,NIH, Bethesda, Maryland, USA; 4CBEL,CIT,NIH, Bethesda, Maryland, USA
A double Pulsed Gradient Spin Echo (d-PGSE) filtered MRI sequence was propose to detect local anisotropy in heterogeneous systems. The sequence was first tested on a macroscopically isotropic, microscopically anisotropic “gray matter” phantom, which consists of randomly immersed tubes filled with water, and then applied on a formalin fixed spinal cord. Local anisotropy was observed in both the gray matter phantom and spinal cord specimen using b-values readily achievable on clinical scanners. This finding suggests a potential use of this contrast mechanism.
|17:36||764.||Double Wave Vector Diffusion Weighting in the Human
Corticospinal Tract in Vivo
Martin A. Koch1, Jürgen Finsterbusch1
1University Medical Center Hamburg-Eppendorf, Hamburg, Germany
Diffusion weighting with two successive gradient pulse pairs of different direction can be used to derive information about tissue structure that is not easily available otherwise, e.g. cell size and shape. To date the underlying effect has only been demonstrated in vitro. The in vivo results presented here support the notion that the predicted effect can be observed in human brain tissue in vivo on a clinical MR system.
Magnetization Transfer Prepared Diffusion Tensor
Alexandru Vlad Avram1, Arnaud Guidon1, Allen W. Song1
1Duke University, Durham, North Carolina, USA
Traditional DTI methods usually do not offer specific selectivity regarding the origin of the connectivity changes. In this report, we incorporate a magnetization preparation pulse into the conventional diffusion tensor imaging to provide additional selectivity to proton pools modulated by the macromolecules. It is shown that changes in diffusion tensor can be robustly detected that are suggestive of their origin in macromolecular structures such as myelin. It is hoped that this additional selectivity using DTI can be used to investigate the pathological processes (e.g demyelination) in many white matter diseases (e.g. multiple sclerosis, ALS, autism).