[Insight-users] is DICOM volume origin calculation correct?

[marianabb]

Hello,

I am using ITK-4.3.2 to create a volume from a stack of DICOM single-frame
images of the heart.

Most of the code is taken from the example DicomSeriesReadImageWrite2.cxx,
and the basics work, but I'm confused about whether the volume origin
produced is correct. 

The volume is composed of 14 slices, with spacing [1.0, 1.0, 8.0], the first
and last slices have the following origins (Image Position Patient, DICOM
tag 0020,0032):
- First slice: 42.021, -174.562, 159.592
- Last slice: -27.608, -102.908, 188.461

The resulting file created with ITK has the last slice IPP as the image
origin, but if I open the original DICOM files with Slicer or Matlab the
resulting image has the first slice IPP as the origin.

I thought that maybe ITK was just using the IPP of the last file it read,
but if I read the slices in the opposite order (last slice as first as so
on) the resulting origin is still the same as before.

I understand also that Slicer and DICOM files use the top-left voxel as the
origin, while ITK uses the bottom-left voxel, but this still doesn't explain
using the last slice IPP.

Any thoughts on this matter would be of great help.

Thanks!
--
Mariana



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