[Insight-users] Urgent: Strange dicom imageIO

[Miller, James V (GE, Research)]

Mathieu,

Defaulting slope/intersept to 1/0 will result in a loss of precision of PET data.
The slopes in PET are established on a per slice basis to maximize the precision 
in the 16bits stored on disk.  So if we read in a PET series and write it out with
a slope of 1/0 we'll loose precision. on some of the slices.

Just something we should think about.

Jim

-----Original Message-----
From: Mathieu Malaterre [mailto:mathieu.malaterre at kitware.com]
Sent: Thursday, May 11, 2006 10:54 AM
To: Miller, James V (GE, Research)
Cc: insight-users at itk.org
Subject: Re: [Insight-users] Urgent: Strange dicom imageIO



> When writing DICOM, ITK does not undo this mapping.  This is the problem
> that you are seeing.  We have been struggling on how to address this issue.
> If the slope/intersept are specified in the meta data, we put these values
> into the DICOM header.  But we do not unapply this pixel transform. So if 
> you read this data back in, it essentially has had the slope/intersept applied
> twice!

I think that in all cases ITK when writing data is writing in the proper 
units. Therefore the slope/intercept should simply be set to 1,0. I 
don't see any case where the image would be loaded/manipulated in the 
non-units (aka raw stored pixel value, before slope/intercept) then 
written to disk.

Comments welcome
Mathieu