DICOM PS3.3 2021c - Information Object Definitions

C.36.12 RT Delivery Device Common Module (Current)
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### C.36.12 RT Delivery Device Common Module

The RT Delivery Device Common Module contains general information pertaining to the physical device used to deliver the treatment.

Table C.36.12-1. RT Delivery Device Common Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Include Table C.36.2.2.1-1 “Treatment Device Identification Macro Attributes”.
Radiation Dosimeter Unit Sequence | (300A,0658) | 1 | Measurement units of the machine dosimeter. Only a single item shall be included in this Sequence.
>Include Table 8.8-1 “Code Sequence Macro Attributes”. | CID is specified in the IOD
RT Device Distance Reference Location Code Sequence | (300A,0659) | 1 | Point of reference used for measuring the distance to various devices. Only a single item shall be included in this Sequence.
>Include Table 8.8-1 “Code Sequence Macro Attributes”. | DCID 9544 “Radiotherapy Distance Reference Locations”.
RT Beam Modifier Definition Distance | (300A,0688) | 1 | Absolute distance in mm along the z-axis of the Base Beam Modifier Coordinate System from the reference location as specified by RT Device Distance Reference Location Code Sequence (300A,0659) to the Base Beam Modifier Definition Plane. The value shall be greater than or equal to zero. See Section C.36.1.1.9.
Equipment Frame of Reference UID | (300A,0675) | 1 | Frame of Reference identifier for the Treatment Delivery Device. See Section C.36.12.1.1.
Equipment Frame of Reference Description | (300A,0676) | 3 | Description of Equipment Coordinate System identified by the Equipment Frame of Reference UID (300A,0675). See Section C.36.12.1.2.
Equipment Reference Point Coordinates Sequence | (300A,0677) | 2 | Coordinates of device-specific reference points. Zero or more Items shall be included in this Sequence.
>3D Point Coordinate | (0068,6590) | 1 | Coordinates (x,y,z) in mm of the device-specific reference point in the Equipment Coordinate System.
>Equipment Reference Point Code Sequence | (300A,0678) | 1 | Identifies the type of reference point. Only a single Item shall be included in this Sequence.
>>Include Table 8.8-1 “Code Sequence Macro Attributes”. | DCID 9554 “Equipment Reference Points”.
Include Table C.36.2.2.2-1 “RT Patient Support Devices Macro Attributes”.

#### C.36.12.1 RT Delivery Device Common Module Attribute Descriptions

##### C.36.12.1.1 Equipment Frame of Reference UID

The Equipment Frame of Reference UID (300A,0675) identifies the Equipment Coordinate System for a Treatment Delivery Device, see Section 10.39.1.1.

The RT Radiation SOP Classes are bound by the Standard to specific Well-known Frames of Reference as defined in Table A-2 in PS3.6 . For C-Arm based devices delivering radiation at a single machine isocenter this may be the [IEC 61217] coordinate system. Devices are calibrated to a specific Well-known Frame of Reference and thus use the corresponding Well-known UID in Equipment Frame of Reference UID (300A,0675).

For RT Radiation SOP Classes the result of the transformation between the Patient-based Coordinate System and the Equipment Coordinate System is used to describe the intended treatment position. If two or more transformation matrices describe the relation between two or more Patient-based coordinate systems and a single Equipment Coordinate System, any calculations assuming transitivity via the Equipment Coordinate System must be performed with great care because the patients anatomy may have changed.

For RT Radiation Record SOP Classes the result of the transformation between the Patient-based Coordinate System and the Equipment Coordinate System is used to describe the actual treatment position. In this case the transformation matrices between different Patient-Based coordinate Systems and a single Equipment Coordinate System shall not be considered transitive from an anatomical point of view and may only be used to compare different treatment positions with respect to the treatment delivery device.

##### C.36.12.1.2 Equipment Frame of Reference Description

The Equipment Frame of Reference Description (300A,0676) is informal and shall not be used for any normative description of the Equipment Coordinate System.

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C.36.11 RT Dose Contribution Module | Home | C.36.12.2 Well-known Frame of Reference For Equipment

DICOM PS3.3 2021c - Information Object Definitions