ELECTRONIC POSTER - ismrm

15:00 4945. RF Concatenation with Spiral In-And-Out Trajectory for Two-Dimensional Large-
Tip-Angle Excitation
Seung-Kyun Lee 1 , Dan Xu 2 , W A. Grissom 3 , Ileana Hancu 1 , Mika W. Vogel 4
1 GE Global Research, Niskayuna, NY, United States; 2 Applied Science Laboratory, GE Healthcare, Waukesha,
WI; 3 Department of Electrical Engineering and Radiology, Stanford University, Stanford, CA; 4 GE Global
Research, Munich, Bavaria, Germany
We demonstrate that the time-reversed RF concatenation principle, which was previously considered in one-dimensional nonadiabatic
inversion pulse design, can be extended to multi-dimensional and multi-coil excitation pulses. We present general analytical
formulation of the concatenation principle, and demonstrate its use in (i) simulated inversion in 8-channel parallel transmit, and (ii) invivo
inversion experiment on a single channel system with a human subject. The off-resonance field sensitivity, which is a drawback
of the concatenation method in one dimension, is significantly reduced for two-dimensional excitation when a spiral in- and outtrajectory
is employed.
15:30 4946. Design of Velocity Selective Inversion Pulse for VSASL Using the Shinnar-Le Roux
Algorithm
Kangrong Zhu 1 , Kui Ying 1 , Xinlu Xu 1 , William Grissom 2 , Michael Lustig 2 , John Pauly 2
1 Tsinghua University, Beijing, China; 2 Stanford University, Stanford, CA, United States
A new method which employs the SLR algorithm to generate velocity selective inversion pulse is presented and a design example is
shown. Simulation results demonstrate that the slice profile of the designed inversion pulse is very smooth and that the pulse has good
resistance to B1 inhomogeneity. Phantom studies verified the frequency selectivity and the velocity selectivity of the pulse. All results
imply that the pulse is potentially suitable for use as a tagging pulse in VSASL. The design method enables the pulse designer to
explicitly trade off among important parameters such as slice thickness, pulse duration and pass-band ripple.
Tuesday 13:30-15:30 Computer 116
13:30 4947. Combined Excitation and Partial Saturation to Reduce Inflow Enhancement
Misung Han 1,2 , Brian A. Hargreaves 1
1 Radiology, Stanford University, Stanford, CA, United States; 2 Electrical Engineering, Stanford University,
Stanford, CA, United States
Partially saturating outer slab upstream can reduce inflow enhancement and pulsatile ghost artifacts by preparing flowing spins to a
steady state before entering the imaging slab. However, adding another RF pulse and spoilers increases scan time. Here, we present a
short RF pulse that simultaneously excites the imaging slab and partially saturates the outer slab. This pulse was designed and
demonstrated by phantom and in vivo experiments for the RF-spoiled gradient echo sequence.
14:00 4948. Partial Fourier Accelerated Selective Excitation Improves Pattern Fidelity at 9.4
Tesla
Kaveh Vahedipour 1 , Tony Stöcker 1 , N Jon Shah 1,2
1 Institute of Neuroscience and Medicine, Forschungszentrum Jülich, Jülich, Germany; 2 Department of
Neurology, RWTH Aachen University, Aachen, Germany
Partial Fourier Spatially has so far been only investigated in 1 dimension in form of asymmetric echoes. Recently, we have prposed to
use partial Fourier excitations for higher dimension. This work encloses recent results and considerations.
14:30 4949. T2-Weighted Spin Echo Pulse Sequence That Is Sensitive to Restricted Diffusion
Ziqi Sun 1 , Robert Bartha 2
1 The Ohio State University, Columbus, OH, United States; 2 Robarts Research Institute, London, Ontario,
Canada
A spin-echo (SE) pulse sequence incorporated with two selective adiabatic full passage (AFP) pulse trains separated by a time delay
tau (varying with TE) and located symmetrically on both sides of an amplitude modulated 180 degree refocusing pulse. Apparent T2
and diffusion measurements on a phantom of multi-medium and multi-compartment demonstrated that the customized SE sequence
generated T2-weighted contrast that is specifically sensitive to restricted diffusion in the phantom media in comparison to those of the
conventional SE and CPMG pulse sequences.
15:00 4950. On the Generation of Half-Sinc Pulses for Optimal Excitation Profile
Keith Wachowicz 1 , B. Gino Fallone 2,3
1 Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada; 2 Medical Physics, Cross Cancer
Institute, Canada; 3 University of Alberta
In this work, we perform simulations to explore the effects of fast T2 relaxation on excitation with half-sinc pulses. The generation of
pulses for optimal excitation profiles is explored in terms of optimal flip angle, for which standard reasoning used for longer T2
species will no longer hold. Also, the number of side lobes to generate an optimal excitation profile was investigated, since, unlike the
case of longer T2, using more side-lobes does not necessarily result in a better profile.