[ITK-users] [ITK] meaning of negative spacing

[Francois Budin]

Hello Zein,

ITK was updated and the problem you had with negative spacing should be
corrected. The spacing should not be negative, and if an image with a
negative spacing is loaded, it is assumed that it means that the image
direction should be inverted, which is now automatically done when reading
an image.
To test the latest version of iITK, you can download it from its git
repository:
git clone http://itk.org/ITK.git

Hope this helps,
Francois

On Mon, Oct 24, 2016 at 11:16 AM, Dženan Zukić <dzenanz at gmail.com> wrote:

> Hi Zein,
>
> image position patient is the authoritative tag to reconstruct slice
> spacing and the vector of Z position/orientation. But I am surprised that
> result is negative spacing instead of negative direction cosine
> (orientation vector). Can you provide the offending DICOM file?
>
> Regards,
> Dženan
>
> On Mon, Oct 24, 2016 at 11:12 AM, Zein Salah <zeinsalah at gmail.com> wrote:
>
>> Hi Dženan,
>>
>> thanks for the response.
>>
>> but I still wonder what does this mean. The reason for the question is:
>>
>> The input image is a multiframe dicom, in which the image position
>> patient (0020, 0032)
>> is stored in the header for every frame. and these values are having
>> decreasing values
>> in the z-coordinate. So I am asking myself
>>
>> 1. if the itkimagereader considers this when it reconstructs the 3D
>> volume?
>>
>> 2. if this is the reason for negative z-spacing? if this is the case,
>> I can this to
>> interpret the meaning of the z-spacing.
>>
>>
>>
>>
>> 2016-10-24 16:55 GMT+02:00 Dženan Zukić <dzenanz at gmail.com>:
>> > Hi Zein,
>> >
>> > I suppose you could invert the 3rd row (Z component) of the
>> TransformMatrix
>> > and have the spacing positive. It should have the same effect and is
>> more
>> > logical.
>> >
>> > Regards,
>> > Dženan
>> >
>> > On Mon, Oct 24, 2016 at 8:50 AM, Zein Salah <zeinsalah at gmail.com>
>> wrote:
>> >>
>> >> Hi,
>> >>
>> >> I have a question regarding reading dicom files with itk,
>> >> particularly, multiframe dicom file (all slices in one single file).
>> >>
>> >> I have read an image with itk 4.10 and write it into an mhd-raw image.
>> >> I noticed that the z-spacin is negative.
>> >> What does negative spacing mean?
>> >>
>> >> thanks,
>> >> Zein
>> >> _______________________________________________
>> >> Community mailing list
>> >> Community at itk.org
>> >> http://public.kitware.com/mailman/listinfo/community
>> >
>> >
>>
>
>
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