[Insight-developers] [GDCM] ITK Origin and coordinate system

[Peter Cech]

On Tue, Jan 17, 2006 at 18:06:02 -0500, Bill Lorensen wrote:
> In an experiment I did a few months back, I had 6 MR scans done of the same 
> object in each of the 6 orthogonal directions. I read them in using the 
> current GDCMImageIO  (which transforms the origin using the direction 
> cosines). All of the volumes roughly lined up without any additional 
> transformations.
> 
> If I did not apply the direction cosines, the datasets were all shifted.

I got several MRI scans of head, the same scanning sequence, but taken
at various times over last half-year. My experience is exactly opposite
to yours. With directional cosines applied to origin, there alignment
was very poor (cca. 10cm shift, both in I-S and A-P direction). Today I
tried without directional cosines applied to origin and they aligned
much better, maximum shift was around 5cm and only in S-I direction.

> Go figure,

Yes, go figure...

Regards,
Peter