Hi Andreas,
My understanding is that partial fourier does not affect the echo spacing
(one simply does not acquire those lines of k-space), whereas you are
correct about the effect of parallel imaging, the echo train will be half as
long with a factor of 2.
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Andreas Bartsch
Sent: Friday, March 04, 2011 2:42 AM
To: [log in to unmask]
Subject: [FSL] Unwarping
Hi,
quick question: Am I right that for Partial Fourier Sampling and Parallel
Imaging I need to calculate my effective Echo Spacing (esp) according to:
effective esp = esp*(Partial Fourier Ratio, e.g. 6/8) / PAT-factor (e.g. 2)
?
To me it looks like accounting for Partial Fourier slightly under-unwarps
the distortions whereas not accounting for it messes up the intensities in
the undistorted EPI a bit.
Thanks + cheers,
Andreas
|