C.8.8.5 Structure Set Module
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#### C.8.8.5 Structure Set Module

A structure set defines a set of areas of significance. Each area can be associated with a Frame of Reference and zero or more images. Information that can be transferred with each region of interest (ROI) includes geometrical and display parameters, and generation technique.

Table C.8-41. Structure Set Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Structure Set Label | (3006,0002) | 1 | User-defined label for Structure Set.
Structure Set Name | (3006,0004) | 3 | User-defined name for Structure Set.
Structure Set Description | (3006,0006) | 3 | User-defined description for Structure Set.
Instance Number | (0020,0013) | 3 | A number that identifies this object instance.
Structure Set Date | (3006,0008) | 2 | Date at which Structure Set was last modified.
Structure Set Time | (3006,0009) | 2 | Time at which Structure Set was last modified.
Referenced Frame of Reference Sequence | (3006,0010) | 3 | Sequence describing Frames of Reference in which the ROIs are defined. One or more items are permitted in this sequence. See Section C.8.8.5.1.
>Frame of Reference UID | (0020,0052) | 1 | Uniquely identifies Frame of Reference within Structure Set.
>RT Referenced Study Sequence | (3006,0012) | 3 | Sequence of Studies containing series to be referenced. One or more items are permitted in this sequence. See Section C.8.8.5.4.
>>Include Table 10-11 “SOP Instance Reference Macro Attributes” |
>>RT Referenced Series Sequence | (3006,0014) | 1 | Sequence describing series of images within the referenced study that are used in defining the Structure Set. One or more items shall be included in this sequence.
>>>Series Instance UID | (0020,000E) | 1 | Unique identifier for the series containing the images.
>>>Contour Image Sequence | (3006,0016) | 1 | Sequence of items describing images in a given series used in defining the Structure Set (typically CT or MR images). One or more items shall be included in this sequence.
>>>>Include Table 10-3 “Image SOP Instance Reference Macro Attributes” |
Structure Set ROI Sequence | (3006,0020) | 1 | ROIs for current Structure Set. One or more items shall be included in this sequence.
>ROI Number | (3006,0022) | 1 | Identification number of the ROI. The value of ROI Number (3006,0022) shall be unique within the Structure Set in which it is created.
>Referenced Frame of Reference UID | (3006,0024) | 1 | Uniquely identifies Frame of Reference in which ROI is defined, specified by Frame of Reference UID (0020,0052) in Referenced Frame of Reference Sequence (3006,0010).
>ROI Name | (3006,0026) | 2 | User-defined name for ROI.
>ROI Description | (3006,0028) | 3 | User-defined description for ROI.
>ROI Volume | (3006,002C) | 3 | Volume of ROI (cubic centimeters).
>ROI Generation Algorithm | (3006,0036) | 2 | Type of algorithm used to generate ROI. Defined Terms: AUTOMATIC calculated ROI SEMIAUTOMATIC ROI calculated with user assistance MANUAL user-entered ROI
>ROI Generation Description | (3006,0038) | 3 | User-defined description of technique used to generate ROI.
>Derivation Code Sequence | (0008,9215) | 3 | A coded description of how this ROI was derived. One or more items are permitted in this Sequence. See Section C.8.8.5.3 for further explanation.
>>Include Table 8.8-1 “Code Sequence Macro Attributes”. | Enumerated Value (113085, DCM, "Spatial resampling").
Predecessor Structure Set Sequence | (3006,0018) | 3 | The Structure Set that has been used to derive the current Structure Set. Only a single item is permitted in this sequence.
>Include Table 10-11 “SOP Instance Reference Macro Attributes” |

##### C.8.8.5.1 Frames of Reference

The Referenced Frame of Reference Sequence (3006,0010) describes a set of frames of reference in which some or all of the ROIs are expressed. Since the Referenced Frame of Reference UID (3006,0024) is required for each ROI, each frame of reference used to express the coordinates of an ROI shall be listed in the Referenced Frame of Reference Sequence (3006,0010) once and only once.

### Note

As an example, a set of ROIs defined using a single image series would list the image series in a single Referenced Frame of Reference Sequence (3006,0010) item, providing the UID for this referenced frame of reference (obtained from the source images), and listing all pertinent images in the Contour Image Sequence (3006,0016).

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