Hi - no, it doesn't - that is part of the initial freesurfer processing
(which estimates white matter and then estimates bias field on the basis
of white matter points), not the format conversion.
ttfn, Steve.
On Thu, 29 Aug 2002, Darren Weber wrote:
Dear Bruce et al,
does mri_convert
p.s. what we do is not really bias field estimation/correction, but
something much more aggressive, really a pre-segmentation, which accounts
for bias fields as well as tissue inhomogeneity. If what you want is really
the bias field for some other purpose, you're probably better of using the
EM
I am referring to a command line option to mri_convert:
--unwarp-gradient-nonlinearity ...
- Original Message -
From: Bruce Fischl [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Thursday, August 29, 2002 9:30 PM
Subject: Re: RF bias correction with mri_convert
p.s. what we do is
Hi Bruce, et al,
The Markov random field approach with FSL FAST is intensive (~ 2000 sec on
Athlon 1700, 1Gb PC2700 on VIA KT333A) and the results appear to be good.
Of course, it could be better to measure the quantity on the scanner. Would
this approach require access and modification of the
Hi Darren,
I think you'll find that this option refers to the fact that the
gradients in many of the latest generation MRI systems from several
manufacturers are not exactly linear, particularly in z. Obviously, this
has implications for the imaging experiments performed on them,
Greig is correct. The --unwarp-gradient-nonlinearity option corrects for
the 3-D image distortions caused by departures from linearity in the
magnetic fields produced by the x-, y- and z- gradient coils. These
distortion patterns are specific to each scanner/gradient model (e.g.,
Sonata,
Hi Anders,
Many thanks for this reply. We have been grappling with the
non-linearity on our new Sonata systems, and will face the same hurdle
with our 4T (Sonata gradients). Would it be possible to continue the
discussion off-list about your correction procedure and how it is
implemented in
