Hi all,
I am using prelude and fugue to correct for EPI distortion. I have two
modulus and two phase images corresponding to two gradient echo's with
different TE, and I am using the following command line scripts:
prelude -a modulus_echo01 -p phase_echo01 -u phase01
prelude -a modulus_echo02 -p phase_echo02 -u phase02
fslmaths phase02 -sub phase01 -div 0.0031 fieldmap_rads -odt float
fugue -i EPI_image --loadfmap=fieldmap_rads --dwell=0.000767 -u out
where TE=0.0031 sec and dwell_time=0.000767 sec.
a) Is the above sequence correct?
b) The phase_echo images that are used as input to prelude, should be
scaled in the range 0 to 2*pi or -pi to pi?
c) Should the modulus and phase images be registered first to the EPI
image? They are acquired just after the EPI acquisition with exactly the
same field of view and resolution. Or fugue performs this registration?
Thank you in advance,
Stamatis
Stamatios N Sotiropoulos
Clinical Neurology
University of Nottingham, UK
|