I can't think of a reason to do that. One does need to acquire two echo
times, but not two averages of each.
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Jenifer Juranek
Sent: Monday, September 27, 2010 12:20 PM
To: [log in to unmask]
Subject: [FSL] field map for Philips 3T
I asked my Philips 3T MRI tech to add a field map sequence (gradient echo)
for correcting EPI-related distortions in 32dir 2mm iso ax DTI data with
FUGUE. I was expecting something on the order of 2-3min, but the data I
received is ~6min. It looks like they chose NEX=2. Is there any reason to
collect a field map with NEX=2 instead of NEX=1? Are there specific
parameter ranges available somewhere I could check against to see if some
tweaks here and there can be made to decrease the field map acquisition time
to the 2-3min range?
Many thanks for any suggestions,
Jenifer
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