[vtkusers] What ditermines whether the slice order should be reversed?

[Ramamurthy, Rajesh (GE Global Research, US)]

David,

Another follow-up question. In VTK7.1.1, is there a method to tell  the slice location tag? I found other methods e.g. , for slice spacing but not slice location. Or is there a function that returns all the tags, and we can get the information that way?

Thanks
Rajesh

From: vtkusers [mailto:vtkusers-bounces at vtk.org] On Behalf Of David Gobbi
Sent: Sunday, August 27, 2017 3:30 PM
To: Liu_tj
Cc: vtkusers
Subject: EXT: Re: [vtkusers] What ditermines whether the slice order should be reversed?

Hi Liu Peng,

The vtkDICOMReader sorts according to the Image Plane Module:
http://dicom.nema.org/MEDICAL/dicom/current/output/chtml/part03/sect_C.7.6.2.html
That is, the slices are sorted in a manner such that the VTK image data has a right-handed coordinate system (called an RCS in the link above).

Sorting the slices to get an RCS means that sometimes the slices will be sorted the same as the InstanceNumber, and sometimes they will be sorted opposite to InstanceNumber, depending on the order in which scanner ordered the slices.

You can perform the sorting yourself by calling reader->SortingOff().  If Sorting is Off, the reader will take the slices in the same order as the vtkStringArray that you passed to reader->SetFileNames().

If you send me the block of code where you set up and call the reader, then I might be able to provide more help.  Don't forget to also say what versions of VTK and vtk-dicom you are using.

Cheers,
 - David



On Sun, Aug 27, 2017 at 10:41 AM, Liu_tj <tjlp at netease.com<mailto:tjlp at netease.com>> wrote:
Hi,

I have a question about the DICOM slice order. I use the DICOM reader by David Gobbi to read the slice series to vtkImageData. And I found that the oder is the same as the order by DICOM instanceNumber tag. However, some doctors tell me that the order should be reversed because the scan should start from head to foot.

@David, if I need to reverse, how to achieve that by your DICOM reader?

Thanks
Liu Peng




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