Multi-Band Methods

Wednesday 14 May 2014

Weiran Deng¹, Benjamin Zahneisen¹, and V. A. Stenger^1
1University of Hawaii, John A. Burns School of Medicine, Honolulu, HI, United States

This abstract presents a CAIPIRINHA style sampling using a 3D stack-of-spiral trajectory. By rotating the spiral interleaves along the through-plane direction, the encoding capability of the receiver sensitivities can be better used to improve the g-factor. We show the improved quality of the 3T in vivo human brain images acquired at 20.750.75mm3 resolution using this method. In addition, this abstract presents a 3D GRAPPA method that is used to reconstruct the CAIPIRINHA style under-sampled stack-of-spiral data.

Mayur Narsude^1,2, Daniel Gallichan³, Wietske van der Zwaag³, Rolf Gruetter³, and Jose Marques^3
1LIFMET, EPFL, Lausanne, Vaud, Switzerland, ²University of Lausanne, Lausanne, Vaud, Switzerland, ³CIBM, EPFL, Lausanne, Vaud, Switzerland

This study aimed to demonstrate benefit of highly accelerated 3D-EPI-CAIPI wholebrain fMRI, particularly the ability to filter out respiratory and cardiac noise. Thanks to the use of 3D-EPI-CAIPI sampling patterns, it was possible obtain a 3 and 8 fold increases in temporal resolution in respect to un-accelerated 3D-EPI with only mild g-factor penalty. Temporal SNR per unit of time of the 8-fold accelerated data was ~62% and ~26% higher than un-accelerated and 3-fold accelerated data respectively. Better physiological signals filtering with higher sampling rates resulted in higher statistical significance for resting state networks found via Independent Component Analysis.

Himanshu Bhat¹, Jonathan R. Polimeni², Stephen F. Cauley², Kawin Setsompop², Lawrence L. Wald², and Keith Heberlein^1
1Siemens Medical Solutions USA Inc, Charlestown, MA, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States

Conventional ACS sampling methods for in-plane and simultaneous multi-slice accelerated EPI are susceptible to physiological or bulk subject motion. In this work we propose a novel motion-insensitive ACS acquisition technique called FLEET for highly accelerated EPI. The performance of both conventional and FLEET ACS sampling is evaluated with tSNR analysis done with and without deliberate head nodding performed during ACS acquisition. The conventional method and FLEET give comparable results without motion, however the FLEET method performs better in the presence of motion during the ACS scan.

Bjorn Stemkens¹, Rob H. Tijssen¹, Anna Andreychenko¹, Sjoerd P.M. Crijns¹, Alessandro Sbrizzi², Jan J.W. Lagendijk¹, and Cornelis A.T. van den Berg^1
1Department of Radiotherapy, UMC Utrecht, Utrecht, Netherlands, ²Department of Radiology, UMC Utrecht, Utrecht, Netherlands

Multi-slice CAIPIRINHA can accelerate clinical abdomen scans significantly by exciting multiple slices simulatenously. In this study we determine the optimal shift pattern and slice gap to improve reconstruction and quantify its reproducibility.

Sebastian Schmitter¹, Xiaoping Wu¹, Steen Moeller¹, Dingxin Wang^1,2, Andreas Greiser³, Edward J. Auerbach¹, Lance DelaBarre¹, Pierre-Francois van de Moortele¹, and Kamil Ugurbil^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Siemens Medical Solutions USA, Inc., Minneapolis, MN, United States, ³Siemens Healthcare Sector, Erlangen, Bavaria, Germany

Cardiac MRI may strongly benefit from ultra-high field (UHF) providing higher SNR and intrinsic contrast. However, shorter RF wavelength at UHF results in heterogeneous contrast within the heart. This problem has been successfully addressed with parallel transmission (pTX) using 3D tailored RF excitation ('spokes'). Additionally, respiratory motion often requires breath-hold examinations, which strongly limits spatial coverage. Here we address simultaneously spatial coverage and homogeneity by designing pTX spoke pulses to simultaneously excite/acquire multiple slices ('Multi-Band') using a 16-channel pTX system. We demonstrate successful cardiac CINE multiband acquisitions for 2 slices at 7T and compare 1- and 2-spoke pulse performances.

Kangrong Zhu¹, Robert F. Dougherty¹, Atsushi M. Takahashi², John M. Pauly¹, and Adam B. Kerr^1
1Stanford University, Stanford, CA, United States, ²Athinoula A. Martinos Imaging Center at MIT, McGovern Institute for Brain Research, MIT, MA, United States

In simultaneous multislice (SMS) EPI the ghosting artifacts cannot be accurately corrected in each individual slice if the correction is performed independently of the slice unaliasing. In this work a SMS acquisition is represented as a 3D k-space acquisition, where the k_x dimension is fully sampled and the k_y-k_z plane is undersampled. Eddy current effects that lead to the ghosting artifacts are treated as part of the encoding matrix, allowing both slice unaliasing and eddy current effects to be simultaneously and accurately corrected for with the proposed matrix-decoding method. Parallel imaging reconstruction is also incorporated in the proposed method.

Min-Oh Kim¹, Taehwa Hong¹, and Dong-Hyun Kim^1
1Electrical and Electronic Engineering, Yonsei University, Seoul, Seoul, Korea

Reducing parallel imaging penalty and increasing its acceleration capability by combining two techniques, CAIPIRINHA and View angle tilting.

Djaudat Idiyatullin¹, Curtis A. Corum¹, and Michael Garwood^1
1Radiology, CMRR, University of Minnesota, Minneapolis, MN, United States

This work describes an enhancement of the gapped SWIFT (SWeep Imaging with Fourier Transformation) method utilizing multiple sidebands to achieve highly increased excitation and acquisition bandwidth. The method is called Multi-Band-SWIFT (or MB-SWIFT). Due to its tailored (striped) excitation pattern, MB-SWIFT efficiently uses transmitter power and has increased sensitivity as compared to the other techniques used for “ultrashort TE” imaging. Additionally, MB-SWIFT provides a way to obtain additional information about fast and slow relaxing spins in a single scan. These features make MB-SWIFT an attractive method for numerous MRI applications including musculoskeletal imaging.

Nathan Artz¹, Matthew Smith¹, and Scott Reeder^1,2
1Radiology, University of Wisconsin, Madison, WI, United States, ²Medicine, University of Wisconsin, WI, United States

The purpose of this work was to develop and test multiband RF excitation to accelerate a fully phase encoded (FPE) technique when multiple RF excitations are required to excite a wide range of off-resonance near metallic implants. The femoral head of a hip prosthesis was placed in water and three separate scans were performed with a single RF band, each centered at a different RF offset (-4000, 0, +4000 Hz). The fourth scan used the MB RF pulse to excite all three RF bands simultaneously. This work demonstrates feasibility for reducing scan time using MB excitation near metal with FPE methods.

Bernhard Strasser¹, Gilbert Hangel¹, Marek Chmelík¹, Siegfried Trattnig¹, Stephan Gruber¹, Michal Považan¹, and Wolfgang Bogner^1
1High Field MR Centre, Department of Biomedical Imaging und Image-guided Therapy, Medical University of Vienna, Vienna, Vienna, Austria

In this work the parallel imaging methods slice-Caipirinha and 2D-Caipirinha were combined to (2+1)D-Caipirinha in order to simulate an acceleration of two-slice Hadamard encoded MRSI data of the brain at 7T. The proposed method was compared to standard in-plane acceleration and a reconstruction using 2D-GRAPPA. (2+1)D-Caipirinha was shown to be superior over the standard 2D-GRAPPA acceleration. The original 60 minutes scan could have been reduced with an acceleration factor of 8.7 to clinically relevant scan times of 7 minutes, while still providing enough SNR to quantify tNAA, tCho and tCr.