[Insight-developers] dicom time series

[Ivan Macia]

Hi Richard,

We decide ourselves based on Image Orientation Patient, Image Position
Patient and some other tags as mentioned. For the latter tags we check for
existance first.
One good approach is to use a std::multimap as in gdcm::SerieHelper in order
to sort by IPP and check for duplicate positions. But sometimes (maybe not
in your case) we have found intermixed volumes that need another kind of
heuristic, such as checking a specific DICOM tag (i.e. Acquisition Group).

In the case of MR 3D+t series, we checked for duplicate positions and found
let's say 4, and then we try to find a tag (among a set of predefined tags)
that varies among these images, like Temporal Position Identifier or Echo
Time. Check one of the MR specific tags to see if it varies.

HTH

Iván


2009/2/14 Richard Beare <richard.beare at gmail.com>

> Hi,
> I'll look into these tags.
>
> Do you reconstruct images using ITK once you've decided which dicoms
> belong together, or use some other tool?
>
> On Fri, Feb 13, 2009 at 8:19 PM, Iván Macía <imacia at vicomtech.org> wrote:
> > Dear Richard,
> >
> > In order to distinguish 3D images from 2D+t time series we usually check
> > Image Position Patient. Same Image Position Patient (and Image
> Orientation
> > Patient of course) means it is a time series. I have not worked with MR
> > Phase Contrast myself but other dynamic MR sequences (3D+t) from Siemens
> > have Temporal Position Identifier (0020,0100) and Number of Temporal
> > Positions (0020,0105) DICOM tags. Note that these are optional.
> Otherwise,
> > you may have a look at some other tags like Acquisition Time or
> Acquisition
> > Group but usually it is difficult to find a rule that works for most
> > vendors.
> >
> > DicomWorks software has a nice functionality that shows you which DICOM
> tags
> > vary among the images of the same series so you can have a look to see if
> > any of those is valid to identify the different groups you need.
> >
> > HTH
> >
> > Ivan
> >
> >
> >
> > -----Mensaje original-----
> > De: insight-developers-bounces at itk.org
> > [mailto:insight-developers-bounces at itk.org] En nombre de Richard Beare
> > Enviado el: viernes, 13 de febrero de 2009 3:30
> > Para: insight-developers at itk.org
> > Asunto: [Insight-developers] dicom time series
> >
> > Hi,
> > This question relates to the phase constrast dicom series I mentioned
> > in my last post.
> >
> > These series are a time series of a single slice. My dicom sorting
> > seems to be doing the right thing, but the conversion to nifti does
> > not. The problem is that the time dimension is interpreted as the z
> > dimension, so sequence appears as a 3d voume, rather than a 4d time
> > series with a single slice. At present I'm not sure of the dimension
> > figures that are being passed through the conversion process, so
> > simply permuting the dimensions might not be advisable.
> >
> > Has anyone come across issues of this sort when reconstructing time
> > series? Are there special dicom tags I'm likely to be missing?
> >
> > These are captured on a 1.5T siemens machine.
> >
> > Thanks
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