Which set of updates do you have? If I remember correctly, this was a
temporary bug that has since been fixed. Datatypes for NIfTI files
are now determined according to:
function dt = determine_datatype(hdr)
% Determine what datatype to use for NIfTI images
be = spm_platform('bigend');
if hdr.HighBit>16
if hdr.PixelRepresentation
dt = [spm_type( 'int32') be];
else
dt = [spm_type('uint32') be];
end
else
if hdr.PixelRepresentation || hdr.HighBit>=15
dt = [spm_type( 'int16') be];
else
dt = [spm_type('uint16') be];
end
end
Best regards,
-John
On 17 January 2012 13:57, Michael Marxen <[log in to unmask]> wrote:
> Dear SPM-Developers,
>
> I noticed that the latest SPM8 release Dicom import seems to convert
> EPI-images (Siemens Trio) from int16 (signed) to uint16 (unsigned).
>
> I converted the same file with the 4010 release and it converted (correctly)
> to int16. SPM8 is running under Windows7 and MatlabR2010a.
>
> I only noticed this because MRICroN misinterpretes the intensity of these
> uint16 images by a factor of 2. I think a bug in MRICroN.
>
>
>
> However, SPM should also not do such a type conversion, e.g. in case dicom
> data is negative ( I am not sure that the standard allows that but most
> likely it does because our original dicom files are signed int16. ) . It
> seems safest for an import function not to change data types.
>
>
>
> Is this a bug or intended?
>
>
>
> Best, Michael
>
>
>
>
>
> ------------------------------------------------------------------------------------
>
> Michael Marxen, Ph.D., Dipl.-Phys.
>
> MR Research Physicist and
>
> Technical Co-Director Neuroimaging Centre
>
>
>
> Technische Universität Dresden
>
> Faculty of Medicine Carl Gustav Carus
>
> Department of Psychiatry und Psychotherapy
>
> Section of Systems Neuroscience
>
>
>
> Würzburger Str. 35
>
> 01187 Dresden
>
> Germany
>
>
>
> Phone: +49 (351) 46342212
>
> Fax: +49 (351) 46342202
>
> E-Mail: [log in to unmask]
>
> ------------------------------------------------------------------------------------
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