9.3.2.2 Presentation Context Item Structure
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#### 9.3.2.2 Presentation Context Item Structure

The Presentation Context Item shall be made of a sequence of mandatory fixed length fields followed by a variable field. Table 9-13 shows the sequence of the mandatory fields.

The variable field shall consist of one Abstract Syntax Sub-Item followed by one or more Transfer Syntax Sub-Items.

Table 9-13. Presentation Context Item Fields

Item bytes | Field name | Description of field
--- | --- | ---
1 | Item-type | 20H
2 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
3-4 | Item-length | This Item-length shall be the number of bytes from the first byte of the following field to the last byte of the last Transfer Syntax Item. It shall be encoded as an unsigned binary number.
5 | Presentation-context-ID | Presentation-context-ID values shall be odd integers between 1 and 255, encoded as an unsigned binary number. For a complete description of the use of this field see Section 7.1.1.13.
6 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
7 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
8 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
9-xxx | Abstract/Transfer Syntax Sub-Items | This variable field shall contain the following sub-items: one Abstract Syntax and one or more Transfer Syntax(es). For a complete description of the use and encoding of these sub-items see Section 9.3.2.2.1 and Section 9.3.2.2.2.

##### 9.3.2.2.1 Abstract Syntax Sub-Item Structure

The Abstract Syntax Sub-Item shall be made of a sequence of mandatory fixed length fields followed by a variable field. Table 9-14 shows the sequence of the mandatory fields.

Table 9-14. Abstract Syntax Sub-Item Fields

Item bytes | Field name | Description of field
--- | --- | ---
1 | Item-type | 30H
2 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
3-4 | Item-length | This Item-length shall be the number of bytes from the first byte of the following field to the last byte of the Abstract-syntax-name field. It shall be encoded as an unsigned binary number.
5-xxx | Abstract-syntax-name | This variable field shall contain the Abstract-syntax-name related to the proposed presentation context. A valid Abstract-syntax-name shall be encoded as defined in Annex F. For a description of the use of this field see Section 7.1.1.13. Abstract-syntax-names are structured as UIDs as defined in PS3.5 (see Annex B for an overview of this concept). DICOM Abstract-syntax-names are registered in PS3.4.

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