Value Representation corrections related to OL, UC and UR Status Letter Ballot Date of Last Update 2016/03/18 Person Assigned David Clunie Submitter Name Jörg Riesmeier Submission Date 2015/09/19 Correction Number CP-1544 Log Summary: Value Representation corrections related to OL, UC and UR Name of Standard PS3.5, PS3.18, PS3.19 Sup 181 introduced the OL VR but did not make corresponding changes to parts other than PS3.5. Also, it should not have added OL to text describing the packing of bits for Pixel Data and Overlay Data, since it us not used for that role, and did not completely expunge all uses of the word "String" after Other Byte, Word, etc. CP 1031 introduced the UC VR but did not add it to the list of bulk data attributes for WADO-RS; it should be added. CP 1324 introduced the UR VR but did not add it to the list of bulk data attributes for WADO-RS; it should not be added since it is not the expectation that URLs will be that large. Since the term "octet-stream" is used elsewhere, harmonize the usage in PS3.5 by using it in place of "string of bytes" and "sequence of bytes", and use the term "stream" rather than "string" or "sequence" for values that are not bytes and where appropriate for bytes. Correction Wording:

Amend DICOM PS3.5 as follows:

...

DICOM Value Representations

VR Name	Definition	Character Repertoire	Length of Value
...	...	...	...
OB Other Byte	A string of bytesAn octet-stream where the encoding of the contents is specified by the negotiated Transfer Syntax. OB is a VR that is insensitive to Little/Big Endian byte ordering (see ). The string of bytesoctet-stream shall be padded with a single trailing NULL byte value (00H) when necessary to achieve even length.	not applicable	see Transfer Syntax definition
OD Other Double	A stringstream of 64-bit IEEE 754:1985 floating point words. OD is a VR that requires byte swapping within each 64-bit word when changing between Little Endian and Big Endian byte ordering (see ).	not applicable	232-8 bytes maximum
OF Other Float	A stringstream of 32-bit IEEE 754:1985 floating point words. OF is a VR that requires byte swapping within each 32-bit word when changing between Little Endian and Big Endian byte ordering (see ).	not applicable	232-4 bytes maximum
OL Other Long	A stringstream of 32-bit words where the encoding of the contents is specified by the negotiated Transfer Syntax. OL is a VR that requires byte swapping within each word when changing between Little Endian and Big Endian byte ordering (see ).	not applicable	see Transfer Syntax definition
OW Other Word	A stringstream 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 between Little Endian and Big Endian byte ordering (see ).	not applicable	see Transfer Syntax definition
...	...	...	...
UN Unknown	A string of bytesAn octet-stream where the encoding of the contents is unknown (see Section 6.2.2).	not applicable	Any length valid for any of the other DICOM Value Representations
...	....	...	...

... The packing of bits within values of OB, OL or OW Value representation for Pixel Data and Overlay Data is described in Section 8. ...

.... Pixel Data (7FE0,0010) and Overlay Data (60xx,3000) have a VR of OW or OB, depending on the negotiated Transfer Syntax (see Annex A). The only difference between OW and OB being that OB, a string of bytesan octet-stream, shall be unaffected by Byte Ordering (see ). ...

... ... ... The encoding of the Data Elements of the Data Set shall be as follows according to their Value Representations: ... For the Value Representations OB, OL and OW, the encoding shall meet the following specification depending on the Data Element Tag: Data Element (7FE0,0010) Pixel Data may be encapsulated or native. ... If encapsulated, it has the Value Representation OB and is a sequence of bytesan octet-stream resulting from one of the encoding processes. It contains the encoded pixel data stream fragmented into one or more Item(s). ... ...

... The Pixel Data Element, as specified by the DICOM Default Transfer Syntax in Section 10.1, has a Value Representation of OW (Other Word String). ... ...

...

A sequencestream of identical bytes (Replicate Run) is encoded as a two-byte code: < -count + 1 > <byte value>, where count = the number of bytes in the run, and 2 <= count <= 128 and a non-repetitive sequence of bytesoctet-stream (Literal Run) is encoded as: < count - 1 > <Literal sequence of bytesoctet-stream>, where count = number of bytes in the sequencestream, and 1 <= count <= 128. ...

Amend DICOM PS3.18 as follows:

... The study, series, or instance metadata includes all attributes; however, a RESTful Service is permitted to replace the Value Field of an attribute with a BulkDataURL for attributes with Value Representations (VR) of FL, FD, IS, LT, OB, OD, OF, OL, OW, SL, SS, ST, UC, UL, UN, US, and UT. The client can use the BulkDataURL with the RetrieveBulkData action to retrieve the original Value Field of that attribute. The server is not required to replace any attribute with a BulkDataURL; this is intended to allow the server to provide clients with metadata of a reasonably small size by leaving out large data Value Fields. OB, OD, OF, OL, OW and UN Attributes not replaced with a BulkDataURLwith binary Value Fields are encoded as XML Base64 binary values. Some DICOM instances, such as SR documents, may be entirely described in the metadata. ...

... Each attribute object contains the following named child objects: vr: A string encoding the DICOM Value Representation. The mapping between DICOM Value Representations and JSON Value Representations is described in . At most one of: Value: An array containing one of: The Value Field elements of a DICOM attribute with a VR other than PN, SQ, OB, OD, OF, OL, OW, or UN (described in Section F.2.4) The encoding of empty Value Field elements is described in Section F.2.5 The Value Field elements of a DICOM attribute with a VR of PN. The non-empty name components of each element are encoded as a JSON strings with the following names: Alphabetic Ideographic Phonetic JSON DICOM Model objects corresponding to the sequence items of an attribute with a VR of SQ Empty sequence items are represented by empty objects BulkDataURI: A string encoding the WADO-RS URL of a bulk data item describing the Value Field of an enclosing Attribute with a VR of FL, FD, IS, LT, OB, OD, OF, OL, OW, SL, SS, ST, UL, UN, US, or UT (described in Section F.2.6) InlineBinary: A base64 string encoding the Value Field of an enclosing Attribute with a VR of OB, OD, OF, OL, OW, or UN (described in )

...

DICOM VR to JSON Data Type Mapping

VR Name	Type	JSON Data Type
AE	Application Entity	String
AS	Age String	String
AT	Attribute Tag	String
CS	Code String	String
DA	Date	String
DS	Decimal	Number
DT	Date Time	String
FL	Floating Point Single	Number
FD	Floating Point Double	Number
IS	Integer String	Number
LO	Long String	String
LT	Long Text	String
OB	Other Byte String	Base64 encoded stringoctet stream
OD	Other Double String	Base64 encoded stringoctet stream
OF	Other Float String	Base64 encoded stringoctet stream
OL	Other Long	Base64 encoded stringoctet stream
OW	Other Word String	Base64 encoded stringoctet stream
PN	Person Name	Object containing Person Name component groups as strings (see )
SH	Short String	String
SL	Signed Long	Number
SQ	Sequence	Array containing DICOM JSON Objects
SS	Signed Short	Number
ST	Short Text	String
TM	Time	String
UC	Unlimited Characters	String
UI	UID	String
UL	Unsigned Long	Number
UN	Unknown	Base64 encoded stringoctet stream
UR	URI	String
US	Unsigned Short	Number
UT	Unlimited Text	String

...

.... Implementers should in particular pay attention to the PS3.5 rules regarding the value representations of OD, OF, OL and OW.

Amend DICOM PS3.19 as follows:

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DICOM Data Set Macro

Name	Optionality	Cardinality	Description
...	...	...	...
>BulkData	C	1	A reference to a blob of data that the recipient may retrieve through use of the GetData() method, a WADO-RS call or a STOW-RS call. Required if the DICOM Data Element represented is not zero length and an XML Infoset Value, Item, InlineBinary or PersonName element is not present. The provider of the data may use a BulkData reference at its discretion to avoid encoding a large DICOM Value Field as text by value in the Infoset. For example, pixel data or look up tables. There is a single BulkData Infoset element representing the entire Value Field, and not one per Value in the case where the Value Multiplicity is greater than one. E.g., a LUT with 4096 16 bit entries that may be encoded in DICOM with a Value Representation of OW, with a VL of 8192 and a VM of 1, or a US VR with a VL of 8192 and a VM of 4096 would both be represented as a single BulkData element. All rules (e.g., byte ordering and swapping) in PS3.5 apply. Implementers should in particular pay attention the PS3.5 rules regarding the value representations of OD, OF, OL and OW and OF. If the BulkData has a string or text Value Representation, the value(s) of the DICOM Specific Character Set Data Element, if present, might be necessary to determine its encoding.
...	...	...	...
>InlineBinary	C	1	The Value Field of the enclosing Attribute encoded as base64. Required if the DICOM Data Element represented is: not zero length the VR if the enclosing Attribute is either OB, OD, OF, OL, OW, or UN an XML Infoset Value or BulkData XML element is not present Shall not be present otherwise. There is a single InlineBinary Infoset element representing the entire Value Field, and not one per Value in the case where the Value Multiplicity is greater than one. E.g., a LUT with 4096 16 bit entries that may be encoded in DICOM with a Value Representation of OW, with a VL of 8192 and a VM of 1, or a US VR with a VL of 8192 and a VM of 4096 would both be represented as a single InlineBinary element. All rules (e.g., byte ordering and swapping) in PS3.5 apply. Implementers should in particular pay attention to the PS3.5 rules regarding the value representations of OD, OF, OL and OW.

The Normative version of the XML Schema for the Native DICOM Model follows: ... VR = attribute vr { "AE" | "AS" | "AT"| "CS" | "DA" | "DS" | "DT" | "FL" | "FD" | "IS" | "LO" | "LT" | "OB" | "OD" | "OF" | "OL" | "OW" | "PN" | "SH" | "SL" | "SQ" | "SS" | "ST" | "TM" | "UC" | "UI" | "UL" | "UN" | "UR" | "US" | "UT" }