Invalid tag errors


OpenREM versions 0.8 and earlier rely on pydicom 0.9.9 which has recently had a new release, version 1.0. A replacement of pynetdicom is also being worked on and will be called pynetdicom3. When pynetdicom3 is released, OpenREM will be revised to work the two new packages, but as they are both backwards-incompatible with the old versions you must keep using the versions specified by the installation instructions until this happens. (The correct version of pydicom is installed automatically when you install OpenREM).

The DICOM dictionary (the list of all the tags) supplied with pydicom 0.9.9 is old and doesn’t have some of the newer tags that some modalities are starting to include. This can lead to errors when you attempt to import a file with one of these tags, and the file will not be imported.

Error message

The error message will look something like this. The actual tag can be different, this is an example.


KeyError: ‘Invalid tag (0018, 9559): “Unknown DICOM tag (0018, 9559) - can’t look up VR”’


The workaround is to replace the with the version in the current master of pydicom.

First, download the current file (right click ‘Save link as…’ or similar):

Next, find the location of your pydicom install – it should be at one of the following paths:

  • Ubuntu linux: /usr/local/lib/python2.7/dist-packages/dicom/
  • Other linux: /usr/lib/python2.7/site-packages/dicom/
  • Linux virtualenv: vitualenvfolder/lib/python2.7/site-packages/dicom/
  • Windows: C:\Python27\Lib\site-packages\dicom\
  • Windows virtualenv: virtualenvfolder\Lib\site-packages\dicom\

Replace the existing file with the one you have downloaded.

Try and import the file again - it should now work.