C.23.1.1 Attribute Descriptions

C.23.1.1.1 Hanging Protocol Definition Sequence Attributes

The Hanging Protocol Definition Sequence (0072,000C) provides a collection of one or more sequence items that defines the intent for the Hanging Protocol with respect to modality, anatomy, laterality, procedure and/or reason.

This allows for some degree of flexibility in defining the intent for the Hanging Protocol, while providing a precise structure for query matching using the existing rules for Sequence Matching, as defined in PS 3.4.

Notes:1. The Hanging Protocol Definition Sequence (0072,000C) does not imply anything about the related image sets. These are defined in the Image Sets Sequence (0072,0020).

2. When creating a Hanging Protocol Instance, the values that are used for Procedure Code Sequence (0008,1032) or Reason for Requested Procedure Code Sequence (0040,100A) may come from a variety of sources, but are expected to be consistent throughout the domain in which a Hanging Protocol Instance will be exchanged. The following are recommended as potential sources of values.

Procedure Code Sequence (0008,1032):

Reason for Requested Procedure Code Sequence (0040,100A):

C.23.1.1.2 Image Sets Sequence

The Image Sets Sequence (0072,0020) within a Hanging Protocol Instance serves to identify the type of image or other object sets to which the Hanging Protocol is intended to apply. Multiple types of image sets may be identified for a Hanging Protocol, to combine, for example, multiple imaging studies for a specific anatomy, or multiple imaging studies performed over a period of time, to monitor the progress of a condition. All image sets shall be for the same patient.

The images to be included in an Image Set may be specified directly by matching attribute values within the images, or indirectly through Key Object Selection Documents or Presentation States by matching their attribute values.

Key Object Selection Documents shall be matched by their SOP Class UID. The available Key Object Selection Documents may be further matched on the values of their other attributes (e.g., Concept Name Code Sequence, Coding Scheme Designator = “DCM” and Code Value = “113003”, which has a code meaning of “For Surgery”). When the Hanging Protocol Instance is applied, the image object instances referenced by the matching Key Object Selection Document instances comprise the image set.

Presentation States shall be matched by their SOP Class UID. The available Presentation States may be further matched on the values of their other attributes (e.g., Content Label). When the Hanging Protocol Instance is applied, the image object instances referenced by the matching Presentation State instances comprise the image set.

Note: Image Sets Sequence (0072,0020) allows other objects such as waveforms and SR documents to be identified. However, Hanging Protocol Display module operations such as filtering, reformatting, and sorting are defined only for image objects. The only expectation for non-image objects is to associate the objects with a position on a screen.

Each sequence item in the Image Sets Sequence (0072,0020) shall follow these rules:

Notes: 1. The identification of a current image set is established by the application prior to selection of a Hanging Protocol Instance. The current image set is not necessarily from a single study.

2. In mammography screening, for example, the Hanging Protocol defines the current image set plus the screening image set for the patient from the year prior. There would be one sequence item in the Image Sets Sequence (0072,0020). Within this sequence item, the Items of the Image Set Selector Sequence (0072,0022) would identify a mammography screening image set type. The Time Based Image Sets Sequence (0072,0030) would have two sequence items, one to identify the current, and one to identify the prior.

C.23.1.1.3 Image Set Selector Sequence Attributes

The Image Set Selector Sequence (0072,0022) contains sequence items that specify the DICOM attribute tags and values that shall be used to identify the image or other object set.

The Image Set Selector Usage Flag (0072,0024) indicates whether the attribute identified by the Selector Attribute (0072,0026) causes matching to succeed or fail if the attribute is not available in an image object.

Within a sequence item, the Selector Attribute (0072,0026) identifies a DICOM attribute tag that is likely to be present in image or other object instances that are desired for the Image Set. If it is a multi-valued attribute, the Selector Value Number (0072,0028) indicates which value is intended to be used for matching. The Selector Attribute VR (0072,0050) identifies the Value Representation of the Selector Attribute (0072,0026). The value of Selector Attribute VR (0072,0050) determines which attribute of the Hanging Protocol Selector Attribute Value Macro is required to specify one or more desired values for the DICOM attribute tag. If more than one value is specified for the attribute, or more than one sequence item is specified in the Selector Code Sequence Value (0072,0080), then image object instances with a corresponding attribute that matches any one of the values shall be included in the Image Set.

Note: The values used for the Selector Attribute (0072,0026) are intended to identify a type of image set via the general categories of modality, anatomy, procedure intent and/or reason. Therefore the values of the tags represented by Selector Attribute (0072,0026) are likely to be coded terms, enumerated values, defined terms or free text. The use of free text attributes is less desirable, because their values are less predictable for matching.

In an image object, some attributes occur at the top level, or nested within a Sequence or Functional Group Sequence, or both. In addition, a Private Attribute may be identified as a Selector Attribute (0072,0026). The attributes of the Hanging Protocol Selector Attribute Context Macro identify a Sequence, Functional Group Sequence, or Private Group context for the Selector Attribute (0072,0026).

The creator of a Hanging Protocol Instance uses this collection of attributes to identify one type of image set to which the Hanging Protocol is intended to apply. The user of a Hanging Protocol Instance (e.g., softcopy review workstation or pre-fetching application) uses this collection of attributes to match a specific image set to a Hanging Protocol, and/or to determine which image sets need to be retrieved in order to use a Hanging Protocol Instance. The Key Attributes to match against to obtain image sets are specified in the Selector Attribute (0072,0026) and its context in each sequence item.

If the value of the tag represented by Selector Attribute (0072,0026) contains a free text description (i.e., Selector Attribute VR = LO, SH, ST, LT, UT), whether exact or partial matching is used to identify a specific image instance when applying a Hanging Protocol Instance is implementation dependent.