DICOM PS3.5 2016a - Data Structures and Encoding

A Transfer Syntax Specifications (Normative)
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# A Transfer Syntax Specifications (Normative)

## A.1 DICOM Implicit VR Little Endian Transfer Syntax

This Transfer Syntax applies to the encoding of the entire DICOM Data Set. This implies that when a DICOM Data Set is being encoded with the DICOM Implicit VR Little Endian Transfer Syntax the following requirements shall be met:

1. The Data Elements contained in the Data Set structure shall be encoded with Implicit VR (without a VR Field) as specified in Section 7.1.3.

2. The encoding of the overall Data Set structure (Data Element Tags, Value Length, and Value) shall be in Little Endian as specified in Section 7.3.

3. The encoding of the Data Elements of the Data Set shall be as follows according to their Value Representations:

   - For all Value Representations defined in this part, except for the Value Representations OB and OW, the encoding shall be in Little Endian as specified in Section 7.3.

   - 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 has the Value Representation OW and shall be encoded in Little Endian.

       ### Note

       The OL Value Representation is not used for Pixel Data, even if it has a Bits Allocated (0028,0100) of 32, since OL was added to the standard after the encoding of Pixel Data had been established

     - Data Element (60xx,3000) Overlay Data has the Value Representation OW and shall be encoded in Little Endian.

     - Data Element (5400,1010) Waveform Data shall have Value Representation OW and shall be encoded in Little Endian.

     - Data Elements (0028,1201), (0028,1202), (0028,1203), (0028,1204) Red, Green, Blue, Alpha Palette Lookup Table Data have the Value Representation OW and shall be encoded in Little Endian.

       ### Note

       Previous versions of the Standard either did not specify the encoding of Data Elements (0028,1201), (0028,1202), (0028,1203) in this Part, but specified a VR of US or SS in PS3.6-1993, or specified OW in this Part but a VR of US, SS or OW in PS3.6-1996. The actual encoding of the values and their byte order would be identical in each case.

   - Data Elements (0028,1101), (0028,1102),(0028,1103) Red, Green, Blue Palette Lookup Table Descriptor have the Value Representation SS or US (depending on rules specified in the IOD in PS3.3), and shall be encoded in Little Endian. The first and third values are always interpreted as unsigned, regardless of the Value Representation.

   - Data Elements (0028,1221),(0028,1222),(0028,1223) Segmented Red, Green, Blue Palette Color Lookup Table Data have the Value Representation OW and shall be encoded in Little Endian.

   - Data Element (0028,3006) LUT Data has the Value Representation US or OW and shall be encoded in Little Endian.

     ### Note

     Previous versions of the Standard did not specify the encoding of these Data Elements in this Part, but specified a VR of US or SS in PS3.6-1998. A VR of OW has been added to support explicit VR transfer syntaxes. Moreover this element is always unsigned, therefore the VR of SS has been removed. The actual encoding of the values and their byte order would be identical in each case.

   - Data Element (0028,3002) LUT Descriptor has the Value Representation SS or US (depending on rules specified in the IOD in PS3.3), and shall be encoded in Little Endian. The first and third values are always interpreted as unsigned, regardless of the Value Representation.

   - Data Element (0028,1408) Blending Lookup Table Data has the Value Representation OW and shall be encoded in Little Endian.

   - Data Element (0066,0129) Track Point Index List has the Value Representation OL and shall be encoded in Little Endian and is always interpreted as unsigned.

### Note

1. Encoding of Curve Data and Audio Sample Data was previously defined but has been retired. See PS3.5-2004.

2. Vertex Point Index List (0066,0025), Edge Point Index List (0066,0024), Triangle Point Index List (0066,0023) and Primitive Point Index List (0066,0029) were previously defined with a value representation of OW and always interpreted as unsigned, but have been retired. These have been replaced by corresponding OL data elements, which allow values larger than 65535 to index the full range of points that can be encoded in Point Coordinates Data (0066,0016). See PS3.5-2015c.

This DICOM Implicit VR Little Endian Transfer Syntax shall be identified by a UID of Value "1.2.840.10008.1.2".

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DICOM PS3.5 2016a - Data Structures and Encoding