RiiSE20 Conference [postponed] Apr 04, 2020 08:30 AM - 05:00 PM — Chancellor’s Building, Edinburgh BioQuarter
Scottish Clinical Imaging Network (SCIN) Annual Event 2020 [postponed] Apr 30, 2020 09:00 AM - 04:00 PM — Glasgow Caledonian University
NCITA National Conference: Translating Imaging Biomarkers for Improved Patient Outcomes [postponed] May 05, 2020 10:00 AM - 05:00 PM — New Hunt's House, Guy's Campus, King's College London
Scottish Radiological Society Spring Meeting 2020 [postponed] May 15, 2020 09:00 AM - 04:10 PM — Centre for Health Science, Inverness
2020 SINAPSE ASM Jun 19, 2020 09:00 AM - 05:00 PM — Virtual Meeting (online)

eLearning

SINAPSE experts from around Scotland have developed ten online modules designed to explain medical imaging. They are freely available and are intended for non-specialists.


Edinburgh Imaging Academy at the University of Edinburgh offers the following online programmes through a virtual learning environment:

Neuroimaging for Research MSc/Dip/Cert

Imaging MSc/Dip/Cert

PET-MR Principles & Applications Cert

Applied Medical Image Analysis Cert

Online Short Courses

Positive or negative blips? The effect of phase encoding scheme on susceptibility-induced signal losses in EPI

Author(s): C. De Panfilis, C. Schwarzbauer

Abstract:
The observation of blood oxygenation level-dependent (BOLD) effect in functional magnetic resonance imaging (fMRI) studies is often hampered by the presence of magnetic field in homogeneities. These are caused by abrupt changes in the magnetic susceptibility that typically occur near air/tissue interfaces and may result in substantial image distortions and signal losses. In this article, we investigate the effect of susceptibility-induced magnetic field inhomogeneities on the signal intensity (1) and the BOLD sensitivity (BS) for two different phase encoding schemes in blipped echo-planar imaging (EPI), which use either positive (EPIpos) or negative (EPIneg) phase gradient blips for stepping through k-space. Based on magnetic field maps, we generate computer simulations of I and BS for both phase encoding schemes and demonstrate good agreement with the experimental image intensities. We show that regions compromised by susceptibility effects are affected very differently by EPIpos, and EPIneg. Further simulations are performed in two representative regions of interest (orbitofrontal cortex and lower temporal lobe) to investigate the dependence of I and BS on the slice angle (alpha), the magnitude of a moderate compensation gradient applied in the slice direction (G(s)(comp)), and the phase encoding scheme. We find that I and BS can be considerably increased if the appropriate phase encoding scheme is applied in addition to optimizing alpha and G(s)(comp). Our results suggest that this optimization method would be useful in future fMRI studies to improve the sensitivity in regions compromised by susceptibility effects. (C) 2004 Elsevier Inc. All rights reserved.

Full version: Available here

Click the link to go to an external website with the full version of the paper


ISBN: 1053-8119
Publication Year: 2005
Periodical: Neuroimage
Periodical Number: 1
Volume: 25
Pages: 112-121
Author Address: