This is probably a historical thing. Early versions of Analyze did
not have any specific field in the .hdr files that related values in
the files (0-255 or -32768-32767) to true tracer concentrations (as
we were doing only PET back then). Therefore, we invented our own
scalefactor field in the .hdr files. Subsequently, the Mayo added a
couple of fields (dime.cal_max and dime.cal_min) that related tracer
concentration (or whatever units voxels related to) to the maximum
and minimum values in the .img file.
SPM still uses the old scalefactor field, whereas I would guess that
other packages use the official fields (that we leave empty).
Best regards,
-John
| I have a small problem regarding the scale factors of my images after
| spatial normalisation.
|
| The thing is, I have applied a user defined 12-parameter affine
| transformation to a set of
| registered image volumes using ANALYZE. After the transformations are
| complete I save them as
| AnalyzeImage7.5 .
|
| When I then look at these images in MRicro, it is clear that the true image
| intensities, i.e., the scale
| factors are all zero. This results for me in inconsistent image intensities.
| I have tried to change
| the scale factor within MRicro without much success?!
|
| Can anybody help me with this.
|
| I would be grateful if anybody could.
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