Hi,
This isn't really a support forum for mri_convert. That said, since
these are insidious bugs that users of older Siemens data should be aware
of:
1) means that the sign of the bvec for VB15 data may be incorrect. (For
simple tensor fitting, this won't matter. But it would matter if you were
correcting for eddy currents using the 'eddy' tool).
2) means that the bvecs for VB13 data (as defined by the
DiffusionGradientDirection field in the DICOM) are occasionally outright
wrong.
Note that my understanding is that the DicomToNrrd converter has an option
to (re)derive the diffusion direction from the full "B_matrix" entry in
the DICOM, which is a work-around since the B_matrix entry is correct (to
my knowledge) in VB13 DICOMs.
Perhaps others that have had to deal with this issue with VB13 data can
comment on what they did to deal with this bug.
cheers,
-MH
--
Michael Harms, Ph.D.
-----------------------------------------------------------
Conte Center for the Neuroscience of Mental Disorders
Washington University School of Medicine
Department of Psychiatry, Box 8134
660 South Euclid Ave. Tel: 314-747-6173
St. Louis, MO 63110 Email: [log in to unmask]
On 11/10/14 9:57 PM, "M. alshikho" <[log in to unmask]> wrote:
>Hi ,
>I was using MRI Convert to convert my DICOMs in to NIFI files when I got
>these warning message:
>1. "Polarity of the bvecs may be wrong for vb15 data"
>2. "bvecs are sometimes wrong for vb13 data, due to a bug in the
>algorithm by which Siemen's converted the B_matrix to a principle
>eigendirection. use with caution"
>
>Kindly, What is the meaning of each of the previous messages?
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