Offresonance Magnetization Transfer Artifact in SPECIAL at 7T
Alexander Fuchs1, Anke Henning1,
David Brunner1, Peter Boesiger1
1Institute for Biomedical Engineering,
University and ETH Zurich, Zurich, Switzerland
SPECIAL sequence is a 2 step ISIS like
localization scheme that allows to measure 3D SV spectra at very short echo
times. This is especially interesting for spectroscopy at ultra-high fields
were metabolite relaxation complicates the detection of certain metabolites.
It is demonstrated in this work that in SPECIAL without outer volume
suppression the ISIS inversion pulse induces
magnetization transfer effects between bound protons and skull lipids. This
can lead to strong outer volume fat contamination of the actual spectrum.
Furthermore a modification to the SPECIAL sequence is proposed to overcome
these types of artifacts.