DICOM PS3.8 2024b - Network Communication Support for Message Exchange User Information Item Structure

The User Information Item shall be made of a sequence of mandatory fixed length fields followed by a variable field. Table 9-16 shows the sequence of the mandatory fields.

The variable field shall consist of one or more User-Data Sub-Items.


The User-Data Sub-Items may be present in any order within the User-Information Item. No significance should be placed on the order of User-Data Sub-Items within the User Information Item. Sending applications should be aware that some older applications might expect Sub-Items to be encoded in ascending order of Item-type within the enclosing Item.

Table 9-16. User Information Item Fields

Item bytes

Field name

Description of field






This reserved field shall be sent with a value 00H but not tested to this value when received.



This Item-length shall be the number of bytes from the first byte of the following field to the last byte of the User-data field(s). It shall be encoded as an unsigned binary number.



This variable field shall contain User-data sub-items as defined by the DICOM Application Entity. The structure and content of these sub-items is defined in Annex D.

DICOM PS3.8 2024b - Network Communication Support for Message Exchange