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

[Mariana Bustamante]

Hi Bill,

Thanks for the answer.

Maybe that makes sense when reading the image with ITK, but the problem
remains when I write the volume to another file, since ITK modifies the IPP
tag of the DICOM file to be the last slice. As a result, if I open this new
file with Slicer for example, the new origin is the last slice and the
image is in the incorrect position.

Shouldn't ITK use the DICOM standard when writing a DICOM file and use the
first slice origin as the IPP?

Regards,
--
Mariana


On Thu, Aug 8, 2013 at 10:11 PM, Bill Lorensen <bill.lorensen at gmail.com>wrote:

> ITK uses a right handed coordinate system. That is why in this case, the
> last slice is the origin slice. At last that's what I recall.
>
>
>
>  On Thu, Aug 8, 2013 at 1:10 PM, marianabb <marianabb at gmail.com> wrote:
>
>> 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
>>
>>
>>
>> --
>> View this message in context:
>> http://itk-insight-users.2283740.n2.nabble.com/is-DICOM-volume-origin-calculation-correct-tp7583709.html
>> Sent from the ITK Insight Users mailing list archive at Nabble.com.
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>
>
>
> --
> Unpaid intern in BillsBasement at noware dot com
>
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