DICOM PS3.3 2020a - Information Object Definitions

C.36.2.2.12 Compensators Definition Macro (Current)
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##### C.36.2.2.12 Compensators Definition Macro

This Macro defines the geometric configuration elements which cannot vary during delivery.

Table C.36.2.2.12-1. Compensators Definition Macro Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Number of Compensators | (300A,00E0) | 1C | Number of Compensators defined in the Compensator Definition Sequence (300A,0662). Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) equals FULL. May be present otherwise.
Compensator Definition Sequence | (300A,0662) | 1C | Treatment compensator definitions. Required if Number of Compensators (300A,00E0) is present and has a non-zero value. The number of Items included in this Sequence shall equal the value ofNumber of Compensators (300A,00E0).
>Include Table C.36.2.2.3-1 “RT Accessory Device Identification Macro Attributes”. | DCID 9542 “Compensator Device Types”.
>Device Index | (3010,0039) | 1 | Index of the Device in this Sequence. The value shall start at 1 and increase monotonically by 1.
>Referenced Defined Device Index | (300A,0602) | 1C | Device Index value that links the device defined by this Sequence Item to the corresponding device in an RT Radiation Instance. The description of the two devices may or may not be the same. The value is the index of a device in the Compensator Definition Sequence (300A,0662) within the single SOP Instance referenced by Referenced RT Instance Sequence (300A,0631). Required if the Instance referenced in Referenced RT Instance Sequence (300A,0631) contains the device that corresponds to the device defined by this Sequence Item.
>Beam Modifier Orientation Angle | (300A,0645) | 1 | Angle in degrees of the Beam Modifier Coordinate System with respect to the Base Beam Modifier Coordinate System. The angle is a Continuous Rotation Angle, see Section C.36.1.1.5. See Section C.36.1.1.9.
>Compensator Base Plane Offset | (300A,0666) | 1C | The distance in mm between the mounting plane and the base plane of the compensator. The value shall be positive when the base plane is farther away from the reference location (as specified by RT Device Distance Reference Location Code Sequence (300A,0659) ) than the mounting plane. Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) equals FULL. May be present otherwise. See Section C.36.2.2.12.1.2.
>Compensator Map Orientation | (300A,0663) | 1C | Side of the compensator base that the compensator surface shape faces. Enumerated Values: PATIENT_SIDE The compensator surface shape is directed towards the patient. SOURCE_SIDE The compensator surface shape is directed towards the Radiation Source. DOUBLE_SIDED The compensator has two compensator surface shapes which are directed towards the patient and source respectively. Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) equals FULL. May be present otherwise.
>Compensator Shape Sequence | (300A,0668) | 1C | Description of the shape of the Compensator and the fabrication parameters. Required if RT Radiation Physical and Geometric Content Detail Flag (300A,0638) equals FULL. May be present otherwise. Only one Item shall be present.
>>Compensator Divergence | (300A,02E0) | 1 | Whether or not the compensator is shaped according to the beam geometrical divergence. Enumerated Values: PRESENT The compensator is shaped according to the beam geometrical divergence. ABSENT The compensator is not shaped according to the beam geometrical divergence.
>>Material ID | (300A,00E1) | 2 | User-defined identifier for the material used to manufacture the Compensator.
>>Compensator Proximal Thickness Map | (300A,0664) | 1C | A data stream of triplets of x, y and thickness in mm representing a map of the coordinates in the Beam Modifier Definition Plane and thicknesses from the compensator base plane. The order of triplets is not significant. Required if Compensator Map Orientation (300A,0663) is SOURCE_SIDE or DOUBLE_SIDED. See Section C.36.2.2.12.1.1 and Section C.36.2.2.12.1.3.
>>Compensator Distal Thickness Map | (300A,0665) | 1C | A data stream of triplets of x, y and thickness in mm representing a map of the coordinates in the Beam Modifier Definition Plane and thicknesses from the compensator base plane. The order of triplets is not significant. Required if Compensator Map Orientation (300A,0663) is PATIENT_SIDE or DOUBLE_SIDED. See Section C.36.2.2.12.1.1 and Section C.36.2.2.12.1.3.
>>Compensator Shape Fabrication Code Sequence | (300A,0667) | 2 | The method of fabrication, such as shape of tools to be used, surface modelling technique. Zero or more Items shall be included in this Sequence.
>>>Include Table 8.8-1 “Code Sequence Macro Attributes”. | No Baseline CID is defined.
>>Radiation Beam Compensator Milling Tool Diameter | (300A,0669) | 2 | The diameter in mm of the milling tool to be used to create the compensator. The diameter is expressed as the actual physical size and not a size projected on the Beam ModifierDefinition Plane.

###### C.36.2.2.12.1 Compensators Definition Macro Attribute Descriptions

###### C.36.2.2.12.1.1 Compensators Thickness Map and Tray Distance

The thickness values stored in Compensator Proximal Thickness Map (300A,0664) and Compensator Distal Thickness Map (300A,0665) shall be specified parallel to the radiation beam axis if Compensator Divergence (300A,02E0) equals ABSENT, or specified according to the beam geometrical divergence if Compensator Divergence (300A,02E0) equals PRESENT.

###### C.36.2.2.12.1.2 Compensator Base Plane Offset

The compensator base plane is the side of the compensator which is flat. In case of a double-sided compensator, the base plane is the plane from which the compensator thickness is specified.

Figure C.36.2.2.12.1-1. Example of Block and Compensator Geometry

###### C.36.2.2.12.1.3 Compensator Thickness Data Direction

The direction of the rows and columns in Compensator Proximal Thickness Map (300A,0664) and Compensator Distal Thickness Map (300A,0665) is defined as follows: The direction of rows goes along the positive X direction and the direction of the columns goes along the negative Y direction of the Beam Modifier Coordinate System.

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DICOM PS3.3 2020a - Information Object Definitions