ELECTRONIC POSTER - ismrm

particular how it alters the effectiveness of background suppression of static tissue and therefore impacts on the SNR of the ASL
measurement.
14:00 4061. Aliasing, Off-Resonance Saturation, and Residual Signal Analysis for PCASL
Tejas Nair 1 , Rolf Pohmann 2 , Michael Gach 1
1 Research Imaging Facility, Nevada Cancer Institute, Las Vegas, NV, United States; 2 MRT, Max Planck
Institute for Biological Cybernetics, Tuebingen, Germany
The aliasing, off-resonance saturation, and residual signal (control-label) characteristics of pulsed continuous arterial spin labeling
(PCASL) were measured in a 2% agar phantom using various values of label and control RF (B1) and gradient (Gmax) amplitudes.
Aliasing and off-resonance saturation for both the label and control increased with increasing B1 but decreased with increasing Gmax.
The residual signal also decreased with increasing Gmax.
14:30 4062. Correction of Partial Volume Effects in PASL Perfusion Measurements
Marco Pimentel 1 , Pedro Vilela 2 , Inês Sousa 3,4 , Patricia Figueiredo 3
1 Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Lisbon, Portugal; 2 Imaging Department,
Hospital da Luz, Lisbon, Portugal; 3 Instituto Superior Técnico, Lisbon, Portugal; 4 Healthcare Sector, Siemens,
S.A., Portugal
We developed a simple model to correct for partial volume effects (PVE's) in ASL imaging and studied its performance in the
estimation of grey matter (GM) and white matter (WM) perfusion, as well as in the application of ASL to brain activation
measurements in fMRI, in a group of 15 healthy subjects at 3T. Our results reveal the importance of performing an accurate
segmentation in order to achieve a good correction of PVE’s, which can strongly influence the measured GM to WM perfusion ratio
and also the perfusion changes due to activation.
15:00 4063. Effects of Slice Orientation and Parallel Acquisition on EPI-Based PASL Perfusion
Imaging in Areas with Susceptibility Artifact
Shih Yu Cheng 1 , Yuan Yu Hsu 2 , Wan Chun Kuan 3 , Mei Yu Yeh 1 , Kun Eng Lim 2 , Ho Ling
Liu 1,4
1 Medical imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan; 2 Medical Imaging,
Buddhist Tzu Chi General Hospital, Taipei, Taiwan; 3 Biomedical Engineering and Environmental Sciences,
National Tsing Hua University, Hsinchu, Taiwan; 4 Division of Medical Imaging and Intervention, Chang Gung
Memorial Hospital, Taoyuan, Taiwan
ASL MRI using gradient-echo EPI suffers from susceptibility artifact in areas near air/tissue interfaces. Previous fMRI studies
investigated the optimal slice tilt to reduce the signal dropout in those areas. Besides, parallel imaging can help by having shorter
echo trains which reduces intra-voxel dephasing. This study focused on the orbitofrontal cortex region and evaluates the effects of
slice angle combined with parallel imaging on ASL image quality. The results indicated that using parallel imaging could reduce the
signal dropout caused by dephasing effect of susceptibility related field gradient. Parallel imaging is also preferable due to less
subject to slice orientation.
Wednesday 13:30-15:30 Computer 60
13:30 4064. Minimizing Acquisition Time for Quantification of Regional Cerebral Blood Flow
(RCBF) and Arterial Transit Time (ATT) Using Pseudo-Continuous ASL at 3.0T
Yasuhiro Fujiwara 1 , Hirohiko Kimura 2 , Tsuyoshi Matsuda 3 , Tomokazu Ishida 1 , Kyouji
Higashimura 1
1 Radiological Center, University of Fukui Hospital, Fukui, Japan; 2 Radiology, University of Fukui, Fukui,
Japan; 3 GE Healthcare Japan, Tokyo, Japan
The purpose of this study was to evaluate the effect of the number of post labeling delay times and averages to reproduce and
minimize acquisition time for precise rCBF quantification. As result of this study, When performing pCASL at post label delay of 0.5,
1.0, 1.5s, reproducible perfusion images were obtained with sufficient SNR in the condition of 12 averages. Using 3 time points
protocol, scanning time can be minimized as short as 5 minutes.
14:00 4065. A Modified Version of Hrabe-Lewis Model to Account Dispersion of Labeled Bolus
in Arterial Spin Labeling
Onur Ozyurt 1 , Alp Dincer 2 , Cengizhan Ozturk 1
1 Bogazici University, Biomedical Engineering Institute, Istanbul, Turkey; 2 Acibadem University, School of
Medicine, Department of Radiology
We propose a modified version of Hrabe-Lewis model for pulsed arterial spin labeling (pASL) signal and discuss its parameter
estimation in a simulation with a realistic noise data coming from in vivo ASL measurements