I've tried running it with bias correction disabled, and it only gives a
warning message (MATLAB Version 7.1.0.246 (R14) Service Pack 3):
Warning: Matrix is singular to working precision.
> In spm_preproc at 355
I've changed the code locally, so that the warning no longer occurs
(available in next set of updates). Maybe your MATLAB version gives
different errors.
I would suggest that the bias correction of SPM5 should not do too much
harm for data that is already corrected by some other algorithm. For
now, you could just run the algorithm with bias correction, but maybe
with very heavy regularization.
Best regards,
-John
-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
On Behalf Of Kenneth Rando
Sent: Wednesday, June 20, 2007 4:11 PM
To: [log in to unmask]
Subject: [SPM] Segmentation without bias correction
Hello all,
I have T1 images that have already been bias corrected using another
method. When I try to segment in SPM5 using "no correction" I receive
the "matrix singular to working precision or badly scaled" error message
and processing terminates. Is this a bug in the code, or do I need to
change other parameters? As a test I have segmented the same images
using
150mm and the default regularization setting. The processing completes
sucessfully. I am concerned, however, of the effect of running a bias
correction procedure on data already bias corrected using a different
method.
Thanks.
Ken Rando
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