TRADITIONAL POSTER - ismrm

Poster Sessions
2950. Fast T1 Mapping at 7T Using Look-Locker TFEPI
Emma Louise Hall 1 , Ali M. Al-Radaideh 1 , Su Y. Lim 2 , Susan T. Francis 1 , Penny A. Gowland 1
1 Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom;
2 Clinical Neurology, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom
Ultra high field has the benefit of increased SNR to facilitate high resolution imaging. However, the lengthened relaxation time requires long scan times to
produce high resolution T 1 maps due to the need to allow the system to return to equilibrium. Here we present a Look-Locker TFEPI sequence that allows
the acquisition of high resolution, 1.25mm isotropic, T 1 maps with large volume coverage at 7T in less than 6 minutes.
2951. Accelerated Mapping of T1 Relaxation Times Using TAPIR
Klaus Möllenhoff 1 , N Jon Shah 1,2 , Eberhard D. Pracht 1 , Tony Stöcker 1
1 Institute of Neuroscience and Medicine – 4, Medical Imaging Physics, Forschungszentrum Juelich GmbH, Juelich, Germany;
2 Faculty of Medicine, Department of Neurology, RWTH Aachen University, JARA, Aachen, Germany
TAPIR is an extremely flexible Look-Locker sequence that allows choices to be made regarding coverage and number of time points acquired on the
recovery curve. We are using AFP inversion pulses to be more accurate and a segmented EPI readout together with parallel imaging to reduce the total
acquisition time.
2952. Rapid 3D Relaxation Time and Proton Density Quantification Using a Modified Radial IR TrueFisp
Sequence
Philipp Ehses 1 , Vikas Gulani 2 , Peter Michael Jakob 1 , Mark A. Griswold 2 , Felix A. Breuer 3
1 Dept. of Experimental Physics 5, Universität Würzburg, Würzburg, Germany; 2 Department of Radiology, Case Western Reserve
University and University Hospitals of Cleveland, Cleveland, OH, United States; 3 Research Center Magnetic Resonance Bavaria
(MRB),, Würzburg, Germany
The IR TrueFISP sequence has been shown to be a promising approach for the simultaneous quantification of proton density, T 1 and T 2 maps. However,
delays between individual segments are required in order to allow the magnetization to recover, resulting in relatively long scan times. Recently, a modified
IR TrueFISP method has been proposed, which does not necessitate relaxation delays. This method was combined with a radial stack-of-stars acquisition
with golden-ratio based profile order, in order to rapidly obtain a full set of parameter maps of the brain in three dimensions.
2953. The Influence of Finite Long Pulse Correction on DESPOT2
Hendrikus Joseph Alphons Crooijmans 1 , Klaus Scheffler 1 , Oliver Bieri 1
1 Division of Radiological Physics, Department of Medical Radiology, University of Basel Hospital, Basel, Switzerland
The DESPOT2 theory is based on the assumption of instantaneous RF pulses. However, this is a pure theoretical assumption and it can never be met in
practice, only approached with short pulse durations. Explicitly in cases where MT effect reduction is desired, long RF pulses are applied and the assumption
is not met leading to deviation of calculated T 2 from true T 2 values. The implementation of a correction for finite pulse effects in the DESPOT2 theory
makes the method independent of RF pulse duration and marginal deviations of around 1% of the true T 2 are obtained for the calculated T 2 .
2954. Quantification of Transversal Relaxation Time T2 Using an Iterative Regularized Parallel Imaging
Reconstruction
Markus Kraiger 1 , Florian Knoll 1 , Christian Clason 2 , Rudolf Stollberger 1
1 Institute of Medical Engineering, Graz University of Technology, Graz, Austria; 2 Institute for Mathematics and Scientific Computing,
University of Graz, Graz, Austria
Nonlinear parallel imaging reconstruction using an iterative regularized Gauss Newton method has shown its potential in several applications. This technique
determines both the coil sensitivities and the image from undersampled multi-coil data. It enables high acceleration factors without pronounced local
enhancement of noise. The numerical implementation of this sophisticated method requires data normalization steps which are usually performed
individually for each slice and echo. In this study it was investigated if this type of reconstruction is applicable for quantitative imaging despite the complex
reconstruction including image individual normalization. For that purpose high resolution multi-echo imaging with different acceleration factors was used
for the quantification of the transverse relaxation time (T2).
2955. In-Vivo and Numerical Studies of Myelin Water Fraction in Rat Spinal Cord
Kevin D. Harkins 1,2 , Adrienne N. Dula 1,2 , Mark D. Does, 1,3
1 Institute of Image Science, Vanderbilt University, Nashville, TN, United States; 2 Radiology and Radiological Sciences, Vanderbilt
University, Nashville, TN, United States; 3 Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
The myelin water fraction (MWF) estimated from multi-exponential T2 analysis is an effective marker of myelin in tissue, but there is evidence that the
MWF is underestimated due to the exchange of water between myelin and other tissue compartments. In this work, in-vivo experiments confirm a bias in the
MWF within rat spinal cord. Numerical studies further suggest that exchange can account for the variation in MWF, and that exchange between T2
components may be limited by the apparent diffusivity of myelin water.
2956. Evaluation of a Fast T 2 Mapping Method in the Brain
Julien Sénégas 1 , Stefanie Remmele 1 , Wei Liu 2
1 Philips Research Europe, Hamburg, Germany; 2 Philips Research North America, Briarcliff, NY, United States
T2 measurements provide important information about the mobility and chemical environment of water in the tissue of interest. The most frequent method
for accurate T2 quantification uses multi-echo spin-echo (MESE incorporating multiple refocusing pulses in each repetition time following the CPMG
sequence. To cover a wide range of T2 values, the number of spin echoes and corresponding RF pulses needs to be relatively large, resulting in increased
TR, long scan durations, and a high SAR. Recently, a fast T2 mapping method, reducing the total number of phase encoding steps of a MESE sequence
without sacrificing spatial resolution nor the dynamic range of T2 values, was proposed and evaluated in simulations and pre-clinical experiments. In this
work, the accuracy of this acceleration technique for T2 mapping in the human brain was assessed in a larger group of volunteers.