DICOM PS3.3 2021d - Information Object Definitions

C.36.9 Segment Reference Module (Current)
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### C.36.9 Segment Reference Module

The Segment Reference Module references geometrical representations, such as regions of interest, surfaces, lines, or points, which have been associated with a Conceptual Volume.

These referenced representations are referred to as segments.

Table C.36.9-1. Segment Reference Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Segment Reference Sequence | (3010,0021) | 1 | References to segments. One or more Items shall be included in this Sequence. See Section C.36.9.1.3.
>Segment Reference Index | (3010,0022) | 1 | Index of the segment reference in the Sequence. The value shall start at 1 and increase monotonically by 1.
>Direct Segment Reference Sequence | (3010,0023) | 1C | Directly identifies a specific segment in a specific SOP Instance. Required if Combination Segment Reference Sequence (3010,0024) is not present. Only a single Item shall be included in this Sequence. See Section C.36.9.1.3.
>>Include Table 10.33-1 “Conceptual Volume Macro Attributes” |
>>Referenced SOP Sequence | (0008,1199) | 1 | The SOP Instance that contains the referenced segment. Only a single Item shall be included in this Sequence. See Section C.36.9.1.1.
>>>Include Table 10-11 “SOP Instance Reference Macro Attributes” |
>>Referenced Segment Number | (0062,000B) | 1C | Segment Number (0062,0004) in the referenced SOP Instance. Required as described in Section C.36.9.1.1. Only a single Item shall be included in this Sequence.
>>Referenced Fiducials UID | (3010,0031) | 1C | Fiducials UID (0070,031A) in the referenced SOP Instance. Required as described in Section C.36.9.1.1. See Section C.36.9.1.1.
>>Referenced ROI Number | (3006,0084) | 1C | ROI Number (3006,0022) in the referenced SOP Instance. Required as described in Section C.36.9.1.1. See Section C.36.9.1.1.
>>Referenced Surface Number | (0066,002C) | 1C | Surface Number (0066,0003) in the referenced SOP Instance. Required as described in Section C.36.9.1.1. See Section C.36.9.1.1.
>Combination Segment Reference Sequence | (3010,0024) | 1C | Defines a segment as a combination of other segment Items present in the Segment Reference Sequence (3010,0021). Required if the Direct Segment Reference Sequence (3010,0023) is not present. Only a single Item shall be included in this Sequence. See Section C.36.9.1.3.
>>Include Table 10.34-1 “Conceptual Volume Segmentation Reference And Combination Macro Attributes” | See Section C.36.9.1.2.
>>Segmented Property Category Code Sequence | (0062,0003) | 2 | Sequence defining the general category of the property the segment combination represents. Zero or one Item shall be included in this Sequence.
>>>Include Table 8.8-1 “Code Sequence Macro Attributes” | BCID 7150 “Segmentation Property Categories”.
>>Segmented Property Type Code Sequence | (0062,000F) | 1C | Sequence defining the modifier of the property type the segment combination represents. Required if Segmented Property Category Code Sequence (0062,0003) has a value. Only a single Item shall be included in this Sequence.
>>>Include Table 8.8-1 “Code Sequence Macro Attributes” | BCID 7151 “Segmentation Property Types”.
Referenced Spatial Registration Sequence | (0070,0404) | 1C | Registrations between Frames of Reference of Instances referenced in the Referenced SOP Sequence (0008,1199) in the Direct Segment Reference Sequence (3010,0023). Required if any Item in the Combination Segment Reference Sequence (3010,0024) combines segments that do not have the same Frame of Reference UID (0020,0052). May be present otherwise. One or more Items shall be included in this Sequence.
>Include Table 10-11 “SOP Instance Reference Macro Attributes” |

#### C.36.9.1 Segment Reference Attribute Descriptions

##### C.36.9.1.1 Segmentation SOP Instance Reference Sequence

Only the SOP Classes contained in Table C.36.9-2 shall be referenced.

Table C.36.9-2. Permitted SOP Classes

SOP Class Name | SOP Class UID | Referenced Attribute | Required Referencing Attribute
--- | --- | --- | ---
Segmentation Storage | 1.2.840.10008.5.1.4.1.1.66.4 | Segment Number (0062,0004) | Referenced Segment Number (0062,000B)
Surface Segmentation Storage | 1.2.840.10008.5.1.4.1.1.66.5 | Segment Number (0062,0004) | Referenced Segment Number (0062,000B)
Spatial Fiducials Storage | 1.2.840.10008.5.1.4.1.1.66.2 | Fiducials UID (0070,031A) | Referenced Fiducials UID (3010,0031)
RT Structure Set | 1.2.840.10008.5.1.4.1.1.481.3 | ROI Number (3006,0022) | Referenced ROI Number (3006,0084)
Surface Scan Mesh Storage | 1.2.840.10008.5.1.4.1.1.68.1 | Surface Number (0066,0003) | Referenced Surface Number (0066,002C)
Surface Scan Point Cloud Storage | 1.2.840.10008.5.1.4.1.1.68.2 | None | None

The column Referenced Attribute identifies the Attribute used to identify the geometric representation in the SOP Instance referenced in the Segmentation Referenced SOP Sequence (0008,1199).

Depending on the SOP Class UID (0008,0016) in the Referenced SOP Sequence (0008,1199) the corresponding attribute as specified in the Required Referencing Attribute column is required to be present.

It is anticipated that in future additional referencing Attributes may be needed to accommodate new representations of segmentations. Hence the collection of Required Referencing Attributes in Table C.36.9-1 Segment Reference Module Attributes and the conditionally required Type 1C Attributes in the Segment Reference Module may be extended.

##### C.36.9.1.2 Combination Segment Reference Sequence

A Conceptual Volume may be expressed as a combination of other segmented Conceptual Volumes. Those other segments are referenced in the Conceptual Volume Segmentation Reference and Combination Macro (see section 10.34).

The Conceptual Volume Combination Flag (3010,000E) shall be YES. The Conceptual Volume Segmentation Defined Flag (3010,0010) shall be NO. The Conceptual Volume Constituent Segmentation Reference Sequence (3010,0012) in the Conceptual Volume Constituent Sequence (3010,0008) shall not be present since the segmented representation of a constituent of a combination is specified by an Item of the Segment Reference Sequence (3010,0021) as follows: If a constituent in the Conceptual Volume Constituent Sequence (3010,0008) is a combination its constituents must

- either contain a reference to an Item in the Segment Reference Sequence (3010,0021) which contains a Direct Segment Reference Sequence (3010,0023), or

- be present in an Item of the Segment Reference Sequence (3010,0021) which contains the Combination Segment Reference Sequence (3010,0024).

All Conceptual Volume References in this Macro shall reference only segments that are defined in Items in the Direct Segment Reference Sequence (3010,0023).

##### C.36.9.1.3 Conceptual Volumes

The Conceptual Volume UIDs of the Conceptual Volumes instantiated in either the Direct Segment Reference Sequence (3010,0023) or the Combination Segment Reference Sequence (3010,0024) shall be unique within the Segment Reference Sequence (3010,0021).

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DICOM PS3.3 2021d - Information Object Definitions