Re: DICOM RDF: VR "OB or OW"

Hi Detlef,

Yes, it would prevent us.  I looked through the data elements table
https://dicom.nema.org/medical/dicom/current/output/html/part06.html#table_6-1

and most are singular VR types.  There are quite a few ( US or SS ) but
resolvable with xsd:short and xsd: unsignedShort.
But, we have ChannelMinimumValue and ChannelMaximumValue (for example)
which are both ( OB or OW ).
We wouldn't have a way of figuring out what the original VR type was even
with the ontology as it would be
ambiguous.

Which pushes us back to:

1) ?s dcm:someProperty [ dcm:vr "OW"; dcm:Value ( "
DEADBEEF..."^^xsd:base64Binary ) ] .
or
2) ?s dcm:someProperty ( "DEADBEEF..."^^dcm:OW ) .

Perhaps we use the above as a fall back when there is ambiguity?

   - Erich


==========================================================
Erich Bremer, M.Sc.
Director, Applied Informatics
Department of Biomedical Informatics
Stony Brook Medicine
Tel. : 1-631-444-3560
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On Thu, Jul 11, 2024 at 12:46 PM Detlef Grittner <detlef.grittner@sohard.de>
wrote:

> Hi Erich,
>
> I have to come back to this issue of "OB or OW".
>
> The VR OB is defined as follows in the DICOM standard:
> "An octet-stream where the encoding of the contents is specified by the
> negotiated Transfer Syntax. OB is a VR that is insensitive to byte
> ordering (see Section 7.3). The octet-stream shall be padded with a
> single trailing NULL byte value (00H) when necessary to achieve even
> length."
>
> And the VR OW is defined as follows:
> "A stream of 16-bit words where the encoding of the contents is
> specified by the negotiated Transfer Syntax. OW is a VR that requires
> byte swapping within each word when changing byte ordering (see Section
> 7.3)."
> (
> https://dicom.nema.org/medical/dicom/current/output/html/part05.html#sect_6.2
> )
>
> We can resolve the problem of the endianess of OW by strictly using
> little endian and the DICOM standard supports it: "All nonretired
> Transfer Syntaxes in DICOM require the use of Little Endian Byte
> Ordering."
> (
> https://dicom.nema.org/medical/dicom/current/output/html/part05.html#sect_7.3
> )
>
> But if we use xsd:base64Binary, we still have the problem if a single
> value from the stream is a byte (8-Bit) for OB or 2 bytes (16-bit) for OW.
>
> Would this prevent us from relying solely on xsd datatypes and DICOM
> standard/ontology for standard attributes?
>
> Regards,
>
> Detlef
>
> --
> Detlef Grittner, MSc ISM, M.A.
> CTO
>
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