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Double-Dollar ('$$') Character Issues... PreviousNext
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 Link to this message Kyle William Harrison  posted on Wednesday, October 19, 2016 - 11:40 am Edit Post Delete Post Print Post
I've recently taken on a new role with a national diagnostics provider who use MRI scanners from a variety of manufacturers across numerous static and mobile sites.

A 3rd-party reporting house has been experiencing problems with images from one particular scanner - a Vantage Titan 1.5T.

I am told, although this isn't conclusive, that the problems stems from double dollar ('$$') characters within the Study Instance UID.

Has anyone else on the forum had experience of this problem and/or any suggestions in how to fix the problem?
 Link to this message Alexander Peck  posted on Thursday, October 20, 2016 - 01:49 am Edit Post Delete Post Print Post
Morning Kyle,

Valid DICOM UIDs can only contain digits (and full stops).
If there are dollar signs within the actual UIDs then whichever piece of machinery is placing them there is not compliant...

 Link to this message Graham King  posted on Thursday, October 20, 2016 - 08:47 am Edit Post Delete Post Print Post
Hi Kyle.

The two most likely candidates for creating these are the Modality Worklist Provider or the scanner itself.

I'd second what Alex says. DICOM Part 6, Table 6-1 shows that Study Instance UID (0020,000D) is of datatype (VR) 'UI'

The valid values for UI are specified in Part 5, Table 6.2-1 and are as Alex has already stated.

This section also states that the limit for VR datatype of UI is 64 bytes.

I have seen MWL Providers generate Study UIDs of >64 bytes, particularly if the MWL provider attempts to create uniqueness by deriving the UID from an already-long Accession Number.

You don't say if the $$ are at the end of the UID sequence or inserted in the middle. If they're at the end, they could represent some kind of truncation character - just a thought.

In any case, an inspection of the MWL Provider DICOM tracing log should confirm whether or not the MWL Provider is generating the $$ or not.

Once you've isolated the source of the non-compliant UIDs, you can go to the vendor in question armed with the two DICOM references above and require them to fix it.

Best wishes
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