[Insight-users] RE: RE: 3D Image Volume Origin

[Andrew Li]

Hi, Frank:

Thank you very much for spending your time on this issue.

Half of our data is near coronal neurology MRI data. Typical image
dimension (size) is (256,256,160) and pixel size is about (1,1,1.6) mm.
Data is usually acquired with image data center close to the magnet
center. Data is stored as DICOM series with Img-ori-pat tag (0020|0037)
close to 1\0\0\0\0\-1 and Img-pos-pat tags varying from about (-128,
-126, 128) to about (-128, 126, 128). When data is loaded from Anterior
to Posterior, the norm will be close to 0\1\0. 

When we use itkImage and itkGDCMImageIO to load images,
In ITK 2.4.0, the origin is like:
	imgOrigin=-128.982467,-128.983739,-126.400000
while in ITK 2.6.0, the origin is like:
	imgOrigin=-128.982467,-126.400000,128.983739
The difference is a rotation that is applied to the origin in ITK 2.4.0.

As an example, since now the value of the origin in slice direction of
about whole FOV off, any code assumes the coordinate system center is
near image data center will break.

Since itkImage is a very basic class of our package, we hesitate to
change it to itkOrientedImage right now, especially before the ITK SW
guide is updated.

In the mean time, we added back the rotation to the origin. Hope it will
work for us right now and near future.

Thanks again for your help!

-Andrew

-----Original Message-----
From: Frank Miller [mailto:frankmiller at jhmi.edu] 
Sent: Monday, April 17, 2006 9:21 AM
To: Andrew Li
Cc: insight-users at itk.org
Subject: Re: [Insight-users] RE: RE: 3D Image Volume Origin

Andrew,

Personally, I dont understand why the origin is handled the way it is in

the 2.4 code. It seemed like a bug to me. I would be interested to know 
more details about why the 2.6 code is causing you problems.

I would expect most people would agree that something should be done to 
maintain compatibility with itkImage as the library moves toward 
itkOrientedImage but I dont know enough about ITK (and medical images in

general) to judge the merit of your suggestion.

Frank
 
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