[Insight-users] GDCM orientation issue....

[Neil Weisenfeld]

Ah, makes perfect sense. I need to dig a bit deeper to see what is going 
on.  It's possible that the ImagePositionPatient based sorting is 
failing and it silently falls back to filename ordering.

Neil



Simon Warfield wrote:

> My understanding is DICOM guarantees the coordinate system is right 
> handed and that the 'unencoded' direction cosine is the cross-product of 
> the other two.
> This tells you about the axes of the coordinate system.
> ftp://medical.nema.org/medical/dicom/2004/printed/04_03pu3.pdf  page 275 
> guarantees the coordinate system is right handed.
> 
> See also the discussion on Patient Orientation here:
> http://www.faqs.org/faqs/medical-image-faq/part2/
> 
> 
> There is not an obvious way to determine what constitutes 'consecutive' 
> slices or the first and last slices other than from the Image Position 
> (Patient) tag. For example, I don't believe you can infer 'consecutive' 
> from the file name or part of the file name, or from the 'instance 
> number' (a tag with an undefined start value and an undefined ordering 
> but which identifies each image).    All I can see you can do is to sort 
> the slices based on the Image Position (Patient) tag and this will run 
> from the most negative position to the most positive position along the 
> Z axis defined by the direction cosines.
> 
> 
> 
> 
>> I apologise if I'm adding unnecessarily to the pile.
>>
>>
>>
>> Neil
>>
>>
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> 
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