ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore Traditional Poster Session: Acquisition, Reconstruction & Analysis
 1881 Jürgen Finsterbusch1 1Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany T2*-weighted acquisitions used for functional neuroimaging can suffer from through-slice dephasing. Additional, so-called z-shim gradient pulses can be applied in the slice direction to minimize related signal losses. Thereby, a single, slice-specific gradient moment may be sufficient for small target regions like the spinal cord. To combine this z-shimming approach with multi-band acceleration, the individual bands must provide different dephasing moments in the slice direction. This can be realized with appropriate temporal shifts of the individual envelopes as is demonstrated for conventional slice-selective RF excitations and 2D-selective RF excitations for inner-field-of-view imaging. 1882 Rebecca Emily Feldman1, Hadrien A Dyvorne1, Rafael O'Halloran1, and Priti Balchandani1 1Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States The higher signal-to-noise-ratio offered at 7T, has been shown to increase the resolution of diffusion MRI as well as the precision and directional certainty of diffusion-based parameters. Two major drawbacks of 7T dMRI include lengthy acquisitions and signal loss due to B1-inhomogeneity. SMS methods reduce the duration of the acquisition, the refocusing pulses typically used in dMRI are particularly sensitive to B1 non-uniformities leading to a loss in signal, or even complete signal dropout in parts of the image. We have created a dMRI sequence with SEAMS PINS and an EPI readout that provides improved immunity to B1-inhomogeneity. 1883 Samy Abo Seada1, Joseph V Hajnal1, and Shaihan J Malik1 1Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom Simultaneous multi-slice imaging can accelerate image acquisition for commonly used diffusion and functional MRI sequences. The design of multiband pulses can be problematic due to their high peak amplitude. Another issue is that the necessary rapid phase and amplitude modulation can be problematic for some current MRI RF systems to reproduce. Phase related issues can be avoided by designing purely amplitude modulated waveforms. We describe how three current multiband pulse design techniques (phase optimisation, time shifting and root-flipping) can be modified to produce purely amplitude modulated pulses and find that the relative peak increase is only about 20-25%. 1884 Ying Chen1, Song Chen1, Zhong Chen2, and Jianhui Zhong1,3 1Center for Brain Imaging Science and Technology, Zhejiang University, Hangzhou, China, People's Republic of, 2Department of Electronic Science, Xiamen University, Xiamen, China, People's Republic of, 3Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, China, People's Republic of In-plane reduced field-of-view excitation based on two-dimensional radio-frequency pulse (2DRF) has been widely used in many applications. The EPI-style gradient waveform is commonly used in 2DRF implementation. However, at high field, the off-resonance effects during excitation would result in distortions of the profiles obtained. This work is to investigate the feasibility to achieve in-plane selective excitation of anatomically pre-defined regions using SPEN-2DRF pulse under different shim conditions. Experimental results show that the proposed method can produce profiles with significantly improved robustness to distortions at high field than the Fourier-based 2DRF pulse. 1885 Hong Shang1, Hai Luo2, Xia Liu2, Gaojie Zhu2, and Leping Zha2 1Bioengineering, UC Berkeley - UCSF, Berkeley/San Francisco, CA, United States, 2AllTech Medical Systems, Chengdu, China, People's Republic of Two classes of previously proposed nonlinear phase RF pulses, the quadratic-phase pulse and root-flip optimized pulse, are compared in terms of selectivity, peak B1 value, pulse energy, and sensitivity to B1variations, when applied for spatial outer volume suppression. Root-flip pulses have lower peak B1 and energy given the same transition width and pulse duration, or sharper transition given the same peak B1, while quadratic-phase pulses have less sensitivity to B1 variations that maintains profile shape with B1 deviations, and thus less prone to residual saturation band magnetization. This work provides insights to pulse designers in regards to nonlinear phase pulse design and application. 1886 David Y. Zeng1, Jieying Luo1, Dwight G. Nishimura1, and Adam B. Kerr1 1Electrical Engineering, Stanford University, Stanford, CA, United States A B1-insensitive T2-weighted preparation sequence with integrated fat saturation and outer volume suppression for localized cardiac imaging is proposed. The sequence is composed of a BIR-4 90° tip-down pulse, two spectral-spatial adiabatic refocusing pulses and a BIR-4 -90° tip-up pulse. Outer volume suppression is achieved by the spatial selectivity of the first refocusing pulse in x and spatial selectivity of the second refocusing pulse in y. Fat suppression is achieved by spectral selectivity of the refocusing pulses. Numerical simulation and phantom experiments verify the performance of the sequence. 1887 Seohee So1, HyunWook Park1, Dongchan Kim1, Hyunseok Seo1, JaeJin Cho1, Young Woo Park1, and Kinam Kwon1 1Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea, Republic of   Slice profile used for magnetic resonance (MR) imaging has transition region between passband and stopband. Sharper transition performs better slice selection. This abstract proposes method to design short-duration RF pulse without increasing transition region width. Additional phase is merged into a transition region of slice profile. Two RF pulses having different phases are used alternately. The proposed algorithm produces about 30% reduction of RF pulse duration without transition increase. 1888 Lucas Soustelle1, Paulo Loureiro de Sousa1, Sascha Koehler2, Chrystelle Po1, François Rousseau3, and Jean-Paul Armspach1 1Université de Strasbourg, CNRS, ICube, FMTS, Strasbourg, France, 2Bruker BioSpin MRI, Ettlingen, Germany, 3Institut Mines Télécom, Télécome Bretagne, INSERM LaTIM, Brest, France The Variable-rate Selective Excitation (VERSE) approach allows to achieve very short echo time in 2D-UTE sequences when applied on a selective half-pulse and its paired slice selection gradient. Unfortunately, the latter may suffer from non-linearities and eddy current effects, all the more important on preclinical scanners equipped with strong gradient systems.  An efficient method was implemented on a 7T preclinical scanner to measure the real slice selection gradient profile. A reshaping of the corresponding pulse was made, improving the slice selectivity. 1889 Ethan M Johnson1, Kim Butts Pauly2, Pejman Ghanouni2, and John M Pauly1 1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Radiology, Stanford University, Stanford, CA, United States A method for sensitising 3D UTE sequences to the short-$$T_2$$$range of cortical bone using scaled RF hard pulses has been previously demonstrated for creating CT-like contrast in MR imaging. However whole-volume excitation and encoding is not practical in all contexts. Here, an adaptation for slice-selective half-pulses is presented that enables 2D image encoding for MR-simulated-CT images. 1890 Yi-Cheng Hsu1, Ying-Hua Chu1, and Fa-Hsuan Lin1 1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan A new simultaneous multi-slice excitation method was proposed to reduce RF power delivery by only concerning slice profiles within the imaging object. Compared to MultiPINS, our approach used only 79% of the RF energy to the same result (slice thickness = 3mm, MB factor = 5, 4 bandwidth time product, excitation duration 6380 $$\mu s$$$). This excitation method was experimentally demonstrated in spin-echo EPI with blipped CAIPI acquisition. 1891 Christoph Stefan Aigner1,2, Christian Clason3, Armin Rund4, and Rudolf Stollberger1,2 1Institute of Medical Engineering, Graz University of Technology, Graz, Austria, 2BioTechMed Graz, Graz, Austria, 3Faculty of Mathematics, University of Duisburg-Essen, Essen, Germany, 4Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria We demonstrate the joint optimization of RF and slice selective gradient shapes with hard constraints such as peak B1 of the pulse and peak slew rate of the gradient via a flexible approach based on optimal control of the full time-dependent Bloch equation and a novel semi-smooth Newton method. The presented approach allows optimization on a fine spatial and temporal grid while enforcing physical and technical limitations on the control variables. The results are validated on a 3T scanner, demonstrating the practical realizability of the presented approach even for short RF pulses. 1892 David G Norris1,2 and Jenni Schulz1 1Donders Institute for Brain Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands, 2Erwin L Hahn Institute, University Duisburg Essen, Essen, Germany This abstract describes the use of pulses that have a quadratic phase profile in the spatial dimension for simultaneous multi-slice imaging. The quadratic profile reduces the peak voltage needed by an amount dependent on the number of simultaneously excited slices. The pulses have to be used as an excitation-refocusing pair, with the refocusing pulse having half the phase gradient. The echoes from each slice are simultaneously refocused and there are no additional constraints on the pulse duration. 1893 Ronald Mooiweer1, Shaihan J Malik2, Joseph V Hajnal2, Nico van den Berg1, Peter R Luijten1, and Hans Hoogduin1 1UMC Utrecht, Utrecht, Netherlands, 2Division of Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom In this work the design of SPINS excitation pulses has been expanded for use in TSE sequences and was compared to dynamic RF shimming using DSC in a standard T2w TSE sequence. We have demonstrated homogeneous 90 degree excitation, but in itself this was not sufficient to make TSE images uniform. Manipulating the refocusing pulses (using DSC) remains a necessity. 1894 Eric Kenneth Gibbons1, John Mark Pauly2, and Adam Bruce Kerr2 1Department of Bioengineering, Stanford University, Stanford, CA, United States, 2Department of Electrical Engineering, Stanford University, Stanford, CA, United States SS-FSE is a robust method for fast image acquisition in areas where there is significant B0 inhomogeneity.  Recent efforts have led to expand the capabilities beyond traditional constraints of SS-FSE meeting the CPMG condition.  In this work, we examine the effects of various RF pulse types on the stability of the signal using a quadratic phase modulation as well as propose using a novel DIVERSE pulse. 1895 Frank Ong1 and Michael Lustig1 1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States We propose a generalized Shinnar-Le-Roux transform that maps $$T_1$$$, $$T_2$$$ and frequency selective pulses to multi-dimensional polynomials. We show that the polynomial mapping is one-to-one and hence designing these RF pulses reduces to multi-dimensional polynomial design. We describe a convex approach to the multi-dimensional polynomial design and show preliminary $$T_2$$\$ and frequency selective pulses.