C.23 Hanging Protocol Specific Modules
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## C.23 Hanging Protocol Specific Modules

The following Sections specify Modules used for Hanging Protocols.

### C.23.1 Hanging Protocol Definition Module

Table C.23.1-1 specifies the Attributes that describe and identify the high level definition of a Hanging Protocol, including its overall purpose, and the types of image sets to which it applies. See Annex V “Hanging Protocols (Informative)” in PS3.17 for further explanation.

Table C.23.1-1. Hanging Protocol Definition Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Hanging Protocol Name | (0072,0002) | 1 | Short descriptor that identifies the Hanging Protocol.
Hanging Protocol Description | (0072,0004) | 1 | Explanation of the objective or intent of the Hanging Protocol.
Hanging Protocol Level | (0072,0006) | 1 | Identifies the level at which this Hanging Protocol is defined, and the intended use. Enumerated Values: MANUFACTURER SITE USER_GROUP SINGLE_USER
Hanging Protocol Creator | (0072,0008) | 1 | Identifies the creator of the Hanging Protocol.
Hanging Protocol Creation DateTime | (0072,000A) | 1 | Date and time on which the Hanging Protocol was created.
Hanging Protocol Definition Sequence | (0072,000C) | 1 | Sequence that defines the type of imaging studies to which this Hanging Protocol applies. One or more Items shall be included in this sequence. See Section C.23.1.1.1.
>Modality | (0008,0060) | 1C | Type of equipment that originally acquired the data used to create images or related objects to which this Hanging Protocol applies. See Section C.7.3.1.1.1 for Defined Terms. Required if Anatomic Region Sequence (0008,2218) is not present. May be present otherwise.
>Anatomic Region Sequence | (0008,2218) | 1C | Sequence that identifies the anatomic region of interest to which this Hanging Protocol applies. One or more Items shall be included in this sequence. Required if Modality (0008,0060) is not present. May be present otherwise.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 4 “Anatomic Region”.
>Laterality | (0020,0060) | 2C | Laterality of the body part to which this Hanging Protocol applies. Enumerated Values: R Right L Left B Both U Unpaired Zero length means not applicable. Required if Anatomic Region Sequence (0008,2218) is present.
>Procedure Code Sequence | (0008,1032) | 2 | Sequence that identifies a procedure to which this Hanging Protocol applies. Zero or more Items shall be included in this sequence.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | No Baseline CID is defined.
>Reason for Requested Procedure Code Sequence | (0040,100A) | 2 | Sequence that identifies a reason for procedure to which this Hanging Protocol applies. Zero or more Items shall be included in this sequence.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | No Baseline CID is defined.
Number of Priors Referenced | (0072,0014) | 1 | Identifies the number of prior image sets used in this Hanging Protocol.
Image Sets Sequence | (0072,0020) | 1 | Sequence describing one or more types of Image Sets to which the Hanging Protocol applies. One or more Items shall be included in this sequence. See Section C.23.1.1.2.
>Image Set Selector Sequence | (0072,0022) | 1 | Sequence containing Image Set selection attributes and values that are used to identify one type of image or object set for the Hanging Protocol. One or more Items shall be included in this sequence. See Section C.23.1.1.3.
>>Image Set Selector Usage Flag | (0072,0024) | 1 | Indicates the behavior of matching against an image object when Selector Attribute (0072,0026) is not available in the image object. Enumerated Values: MATCH If the attribute is not in the image object, consider the image to be a match anyway. NO_MATCH If the attribute is not in the image object, then do not consider the image to be a match.
>>Selector Attribute | (0072,0026) | 1 | Data Element Tag of an Attribute from an Image or other IOD to use for Image Set selection.
>>Selector Attribute VR | (0072,0050) | 1 | The Value Representation of Selector Attribute (0072,0026). See PS3.5 for Enumerated Values of Value Representation.
>>Include Table C.23.4-1 “Hanging Protocol Selector Attribute Context Macro Attributes” |
>>Include Table C.23.4-2 “Hanging Protocol Selector Attribute Value Macro Attributes” |
>>Selector Value Number | (0072,0028) | 1 | Positive integer identifying which value of a multi-valued attribute identified by Selector Attribute (0072,0026) is to be used for Image Set selection. The value 1 identifies the first value. The value zero identifies any value.
>Time Based Image Sets Sequence | (0072,0030) | 1 | Sequence containing time based Image Set selection categories and values that are used to identify one type of image set for the Hanging Protocol per sequence item. One or more Items shall be included in this sequence. The Image Set Selector Sequence (0072,0022) shall be applied to each sequence item to define an image set. See Section C.23.1.1.2.
>>Image Set Number | (0072,0032) | 1 | A monotonically increasing integer, starting from 1, incrementing by one, unique within the Hanging Protocol Instance. ### Note Each item of the Display Sets Sequence (0072,0200) references one Image Set Number (0072,0032).
>>Image Set Selector Category | (0072,0034) | 1 | Category of the Time Based Image Set selector. Enumerated Values: RELATIVE_TIME ABSTRACT_PRIOR
>>Relative Time | (0072,0038) | 1C | Exactly two numeric values, indicating the start and end values of a prior range of instance acquisition times relative to the date and time of a current image set. The units shall be specified in Relative Time Units (0072,003A). The value pair 0\0 shall indicate a current image set. The value pair n\n shall indicate "prior from the instance acquisition time of a current image set by n units". Required if the value of Image Set Selector Category (0072,0034) is RELATIVE_TIME. ### Note A value pair "1\7" with Relative Time Units (0072,003A) of DAYS would indicate the range "prior by 1 to 7 days before a current image set". The VR of this attribute is unsigned, hence future time cannot be represented.
>>Relative Time Units | (0072,003A) | 1C | Units of time for Relative Time (0072,0038). Enumerated Values: SECONDS MINUTES HOURS DAYS WEEKS MONTHS YEARS Required if Relative Time (0072,0038) is present.
>>Abstract Prior Value | (0072,003C) | 1C | Identifies a prior image set in abstract terms. Exactly two integer values, indicating the range of prior studies to include. Each value shall be greater than zero, where 1 indicates the most recent prior and higher values indicate successively older priors. The special value -1 shall indicate the oldest prior. ### Note The value pair n\n indicates the nth prior. The value pair -1\-1 indicates the oldest prior. The value pair m\n indicates the mth through nth priors, where m is the more recent prior. The value pair 1\-1 indicates all priors. The value pair m\-1 indicates the mth prior and all priors older than m. Required if Image Set Selector Category (0072,0034) is ABSTRACT_PRIOR and Abstract Prior Code Sequence (0072,003E) is not present.
>>Abstract Prior Code Sequence | (0072,003E) | 1C | Identifies a prior image set using coded terminology. Only a single Item shall be included in this sequence. Required if Image Set Selector Category (0072,0034) is ABSTRACT_PRIOR and Abstract Prior Value (0072,003C) is not present.
>>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 31 “Abstract Priors”.
>>Image Set Label | (0072,0040) | 3 | Description of the objective of the image set defined by this sequence item.
Hanging Protocol User Identification Code Sequence | (0072,000E) | 2 | Sequence that provides a coded identifier for the person, group, or site for which this Hanging Protocol was defined. Zero or one item shall be included in this sequence. ### Note If a standardized naming schema becomes available, it should be used. Meanwhile, local coding schemes such as employee numbers and department numbers are likely to be used.
>Include Table 8.8-1 “Code Sequence Macro Attributes” | No Baseline CID is defined.
Hanging Protocol User Group Name | (0072,0010) | 3 | Group or site for which this Hanging Protocol was defined.
Source Hanging Protocol Sequence | (0072,0012) | 3 | Sequence that identifies the Hanging Protocol from which this Hanging Protocol was derived, or on which it is based. Only a single Item is permitted in this sequence.
>Include Table 10-11 “SOP Instance Reference Macro Attributes” |

#### 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 PS3.4.

### Note

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):

   - SNOMED codes

   - ICD-10-PCS Procedure Codes

   - Local Codes

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

   - SNOMED codes

   - ICD-9-CM

   - ICD-10-CM

   - Local Codes

##### 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:

- Each sequence item in the Time Based Image Sets Sequence (0072,0030) shall identify one image set, based on time criteria.

- The Items of the Image Set Selector Sequence (0072,0022) shall collectively identify one type of image set.

- One instance of time based criteria combined with the Items of the Image Set Selector Sequence (0072,0022) shall identify one image set.

- The number of image sets identified by a sequence item of the Image Sets Sequence (0072,0020) shall equal the number of items in the Time Based Image Sets Sequence (0072,0030).

- The value of Image Set Number (0072,0032) in each Time Based Image Sets Sequence (0072,0030) sequence item shall be unique across all sequence items of the Image Sets Sequence (0072,0020).

### Note

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 Selector Attribute (0072,0026) causes matching to succeed or fail if the attribute is not available in an image object.

Within a sequence item, 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 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 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 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 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.

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