perhaps I am missing something.
How is it that you started with a negative voxel size?
By definition does it not have to be positive?
From: FSL - FMRIB's Software Library on behalf of Dr Krish Singh
Sent: Thu 7/22/2004 10:23 AM
To: [log in to unmask]
Subject: Re: [FSL] Negative voxel dimensions and Flirt/Fast
Thanks for your reply.
My point was that I had a registered image with -2,2,2, which I am happy
with. Its just that when this image was run through Flirt the resulting
images had voxel dimensions of +2,2,2, which seems inconsistent.
All the best,
On 22/7/04 3:20 pm, "Jason Craggs" <[log in to unmask]> wrote:
> It is my understanding that, regardless of the input image, FSL will convert
> it to match the registered/target image.
> So, if your raw image was 1*1*1 and the template image is 2*2*2, your final
> image will indeed be 2*2*2.
> If I am wrong someone please correct me. It is for this reason that we have
> developed our own template isovoxeled image.
> From: FSL - FMRIB's Software Library on behalf of Dr Krish Singh
> Sent: Thu 7/22/2004 10:13 AM
> To: [log in to unmask]
> Subject: [FSL] Negative voxel dimensions and Flirt/Fast
> Hi there,
> I've got myself into some laterality difficulties with negative voxel
> dimensions. Let me explain what I did:
> 1) Using flirt I registered a radiological axial volume to the FSL T1
> template. avwhd now reports that this has voxel dimensions of -2,2,2 mm
> which is correct I think.
> 2) I took the registered volume generated in the above step and passed it
> through Flirt to generate segmentation maps. avwhd now reports that the
> voxel dimensions for the segmented images are 2,2,2 which I don't think is
> correct as they should be the same as the input image.
> Is the above behaviour expected? It causes me some problems because my
> software, mri3dX, assumes that if you overlay one volume on another and
> their horizontal voxel dimensions have different signs, then it needs to
> flip the laterality of the overlay. In the case of the above, this is
> clearly not the case.
> All the best,
> Dr K.D. Singh
> Senior Lecturer and Convenor of the Neuroimaging Research Group,
> Director, MRI Research Centre,
> Neurosciences Research Institute
> Aston University, Birmingham B4 7ET, U.K.
> Tel/Fax: +44 (0)121 [204 3865/3864]/[333 4220]
> [log in to unmask], http://www.aston.ac.uk/lhs/staff/singhkd/
Dr K.D. Singh
Senior Lecturer and Convenor of the Neuroimaging Research Group,
Director, MRI Research Centre,
Neurosciences Research Institute
Aston University, Birmingham B4 7ET, U.K.
Tel/Fax: +44 (0)121 [204 3865/3864]/[333 4220]
[log in to unmask], http://www.aston.ac.uk/lhs/staff/singhkd/