Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy

Diffusion: Novel Acquisition

Wednesday 14 May 2014
Space 4  16:00 - 18:00 Moderators: Adam W. Anderson, Ph.D., Stefan Skare, Ph.D.

16:00 0662.   In-vivo diffusion q-space trajectory imaging
Carl-Fredrik Westin1,2, Markus Nilsson3, Filip Szczepankiewicz4, Ofer Pasternak1, Evren Ozarslan1, Daniel Topgaard5, and Hans Knutsson2
1Radiology, Brigham and Women's, Harvard Medical School, Boston, MA, United States, 2Department of Biomedical Engineering, Linkoping University, Linkoping, Sweden, 3Lund University Bioimaging Center, Lund University, Lund, Sweden, 4Department of Medical Radiation Physics, Lund University, Lund, Sweden, 5Center for Chemistry and Chemical Engineering, Lund University, Lund, Sweden

Here we study how the choice of diffusion MRI gradient modulation schemes define the geometry and dimensionality of the diffusion encoding. By defining a diffusion encoding tensor, or diffusion measurement tensor, we will in the Gaussian approximation regime bring concepts as single, double, and triple-PFG into a common framework. Careful design of the speed and shape of the q-space trajectory can produce a planar diffusion encoding that is isotropic in the selected plane. The presented work shows that it is possible to perform in vivo circular diffusion encoding imaging of the human brain with a good SNR.

16:12 0663.   
Improved angular resolution at low b-values in Diffusion Spectrum Imaging through Radial acquisition in q-space
Steven Baete1,2 and Fernando Emilio Boada1,2
1Center for Biomedical Imaging, Dept. of Radiology, NYU Langone Medical Center, New York, New York, United States, 2CAI2R, Center for Advanced Imaging Innovation and Research, NYU Langone Medical Center, New York, New York, United States

In the conventional rectangular sampling of q-space in Diffusion Spectrum Imaging, the angular resolution attainable is proportional to the number of shells and the highest b-value acquired. Hence, increasing angular resolution results in acquiring more samples and increasing acquisition time. In this abstract, the angular resolution of the recently proposed radial q-space sampling is shown to be independent of the number of shells acquired above a certain threshold. This results in improved DSI reconstructions at a lower number of shells and at shorter acquisition times, as illustrated by in vivo brain data and computer simulations.

16:24 0664.   Joint k-q Space Compressed Sensing for Accelerated Multi-Shell Acquisition and Reconstruction of the diffusion signal and Ensemble Average Propagator

Jian Cheng1, Dinggang Shen1, and Pew-Thian Yap1
1University of North Carolina at Chapel Hill, chapel Hill, NC, United States

In this work, we propose a unified compressed sensing framework to reconstruct the diffusion signals and propagators from raw data sub-sampled from both q-space and k-space. With the proposed method, we can reduce scanning time in both k-space and q-space, and obtain good reconstruction quality with low RMSE compared to the estimation using fully sampled data.

16:36 0665.   Novel acquisition scheme for diffusion kurtosis imaging based on compressed-sensing accelerated DSI yielding superior image quality
Tim Sprenger1,2, Jonathan I. Sperl1, Brice Fernandez3, Vladimir Golkov1, Ek Tsoon Tan4, Christopher Hardy4, Luca Marinelli4, Michael Czisch5, Philipp Saemann5, Axel Haase2, and Marion I. Menzel1
1GE Global Research, Munich, Germany, 2Technical University Munich, Munich, Germany, 3GE Healthcare, Munich, Germany, 4GE Global Research, Niskayuna, NY, United States, 5Max Planck Institute of Psychiatry, Munich, Germany

In Diffusion Kurtosis Imaging (DKI), the data is sampled in a series of concentric shells in the diffusion encoding space (q-space) and usu-ally suffers from low SNR. In this work a novel acquisition scheme for kurtosis imaging is presented, based on undersampled diffusion spectrum imaging (DSI) followed by a compressed sensing (CS) reconstruction of q-space. The undersampling thereby yields a compara-ble number of q-space sampling points as in standard DKI schemes whereas the CS-based denoising is shown to improve stability and accuracy of the kurtosis tensor estimation.

16:48 0666.   Rotating Short-Axis EPI “blades” as veering diffusion gradient directions with composite reconstruction (RSA)
Yu-Chien Wu1,2 and Chandana Kodiweera1
1Dartmouth College, Hanover, New Hampshire, United States, 2Radiology and Imaging Sciences, Indiana University, Indianapolis, Indiana, United States

We propose a novel sequence, RSA, for fast and high spatial resolution advanced Diffusion-Weighted Imaging (DWI), which has been used widely to assess the integrity and directional information of white matter. Conventionally, DWI uses single-shot spin-echo EPI sequences. However, SS-EPI suffers from geometric distortion and long echo time (TE) with high spatial resolution (e.g, cubic voxel size of 1mm). Moreover, approaches using high and/or multiple b-values demand adequate SNR for accurate estimations. Because only one short-axis blade is acquired per DW direction in the RSA sequence, it reduces geometric distortion, shortens TE to increase signals, and reduces the scan time.

17:00 0667.   Prospective Phase Correction for Diffusion-Weighted SSFP Imaging In Vivo
Rafael O'Halloran1, Murat Aksoy1, Eric Aboussouan1, Eric Peterson1, Anh Van1,2, and Roland Bammer1
1Radiology, Stanford University, Stanford, CA, United States, 2Zentralinstitut für Medizintechnik, Technische Universität München, Munich, Germany

While single-shot EPI remains the workhorse of clinical diffusion-weighted imaging, diffusion-weighted steady state free precession (DW-SSFP) imaging has some attractive properties as acquisitions are pushed to higher-resolution. The price of imaging in the steady state, however, is the undesirable propagation of uncorrected phase errors into the phase coherence pathway tree leading to loss of signal and contrast. The only way to combat this effect is to prospectively correct the phase. In this work an approach to prospectively correct rigid-body-motion induced phase errors in real time is presented and demonstrated to be effective in human volunteers.

17:12 0668.   In vivo high resolution, undistorted diffusion weighted imaging using DSDE-TFE
Tim Schakel1, Hans Hoogduin2, and Marielle Philippens1
1Radiotherapy, UMC Utrecht, Utrecht, Netherlands, 2Radiology, UMC Utrecht, Utrecht, Netherlands

Single shot DW-EPI suffers from geometric distortions and is limited in resolution. A preparation phase (Diffusion sensitized driven equilibrium (DSDE)) which restores the diffusion weighted magnetization along the longitudinal axis allows for additional readout strategies such as TFE. DSDE-TFE can produce distortion free, high resolution diffusion weighted images, also in otherwise difficult areas to perform diffusion weighted imaging such as the neck.

17:24 0669.   
Rapid in vivo ADC Mapping of Hyperpolarized 13C Metabolites on a Clinical 3T MR Scanner
Bertram L. Koelsch1,2, Galen D. Reed1,2, Kayvan R. Keshari3, Robert A. Bok1, Daniel B. Vigneron1,2, John Kurhanewicz1,2, and Peder E. Z. Larson1,2
1Department of Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States, 2UC Berkeley - UCSF Graduate Program in Bioengineering, San Francisco, CA, United States, 3Memorial Sloan-Kettering Cancer Center, NY, United States

Apparent diffusion coefficient (ADC) maps of water have become useful for cancer identification and characterization. The growing field of hyperpolarized13C has also proven to be useful in identifying tumors by measuring the real-time metabolism of hyperpolarized 13C pyruvate to lactate. In this study, we developed a novel diffusion-weighted hyperpolarized 13C EPI sequence on a clinical 3T MR scanner to rapidly obtain ADC maps of hyperpolarized 13C metabolites in vivo. Clinically, ADC mapping of hyperpolarized 13C lactate could allow for improved classification of tumor grade and metastatic potential by measuring both enhanced metabolic flux and differences in lactate’s microenvironment.

17:36 0670.   
Robust 2D Diffusion Weighted Chemical Shift Imaging (DW-CSI) of the human brain at 7T
Ece Ercan1, Aranee Techawiboonwong2, Maarten J. Versluis1, Andrew G. Webb1, and Itamar Ronen1
1C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Electrical Engineering, Mahidol University, Nakornpathom, Thailand

2D Diffusion Weighted Chemical Shift (DW-CSI) Imaging is a challenging method which lacks robustness due to the multi-shot nature of the acquisition, combined with the low SNR and the relatively high gradient strength needed for adequate diffusion weighting of the slow diffusing metabolites. Here, we show for the first time a method that accounts for both amplitude and phase inter-shot fluctuations, and generates robust, reproducible and anatomically meaningful DW-CSI and metabolite ADC maps.

17:48 0671.   
Free-breathing cardiac DTI with simultaneous multi-slice excitation - permission withheld
Constantin von Deuster1,2, Christian T. Stoeck2, Martin Buehrer2, Jack Harmer1, Rachel W. Chan3, David Atkinson3, and Sebastian Kozerke1,2
1Division of Imaging Sciences & Biomedical Engineering, King's College London, London, London, United Kingdom, 2Institute for Biomedical Engineering University and ETH Zurich, University and ETH Zurich, Zurich, Zurich, Switzerland, 3Centre for Medical Imaging, University College London, London, London, United Kingdom

A navigated, simultaneous slice excitation implementation for accelerated free-breathing cardiac diffusion imaging using STEAM is proposed. By using an improved navigator gating strategy and dual-slice excitation, significant gains in scan efficiency are demonstrated. Diffusion tensor maps acquired using the proposed method compare favourably with data from conventional sequential slice breathhold acquisitions.