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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.

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.

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.

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.

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 180^o refocusing pulse.

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.

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.

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.

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.

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).