This Macro describes the configuration of a Beam Limiting Device which cannot vary during delivery.
Table C.36.2.2.19-1. RT Beam Limiting Device Definition Macro Attributes
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Device Index value that links the device defined by this Sequence Item to the corresponding device in an RT Radiation Instance. The device identification of the two devices may or may not be the same. The value is the index of a device in the RT Beam Limiting Device Definition Sequence (300A,064D) 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. |
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Include Table C.36.2.2.3-1 “RT Accessory Device Identification Macro Attributes”. |
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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. If Device Type Code Sequence (3010,002E) contains either (130331, DCM, "Leaf Pairs"), or (130333, DCM, "Single Leaves") the motion of the RT Beam Delimiters is along the x-axis of the Beam Modifier Definition Plane. See Section C.36.1.1.9. |
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Distance in mm from the reference location as specified by RT Device Distance Reference Location Code Sequence (300A,0659) to the proximal end of beam limiting device (collimator) along the beam axis. |
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Distance in mm from the reference location as specified by RT Device Distance Reference Location Code Sequence (300A,0659) to the distal end of beam limiting device (collimator) along the beam axis. |
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Device that uses parallel beam delimiters to limit the beam. Required if Device Type Code Sequence (3010,002E) contains either (130331, DCM, "Leaf Pairs") or (130333, DCM, "Single Leaves"). |
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Number of beam delimiters parallel to the axis of motion. E.g., a beam limiting device jaw pair is represented as 1 parallel delimiter, an MLC with 100 leaf pairs or with 100 single leaves is represented as 100 parallel delimiters. |
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>Parallel RT Beam Delimiter Device Orientation Label Code Sequence |
A code used to identify the orientation of the beam limiting device. |
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>>Include Table 8.8-1 “Code Sequence Macro Attributes”. |
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The operation mode of Parallel RT Beam Delimiters used to define a treatment aperture. |
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Boundaries in mm of parallel beam delimiters. These are defined along the axis perpendicular to the motion of the delimiters of the RT Beam Limiting Device Type (300A,00B8) with respect to the Beam Modifier Coordinate System. The order of values shall increase monotonically. N+1 values shall be provided, where N is the Number of Parallel RT Beam Delimiters (300A,0648). |
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Specifies the mounting side identified by the direction from the tip to the tail of the delimiter parallel to the axis specified by Device Type Code Sequence (3010,002E). Enumerated Values:
Required if Device Type Code Sequence (3010,002E) contains (130333, DCM, "Single Leaves"). |
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Minimum and maximum opening position in mm describing the extent of the aperture when the delimiter is fully open. 2N values shall be provided, where N is the Number of Parallel RT Beam Delimiters (300A,0648). The order of values shall start with the minimum values for all delimiters, followed by the maximum values, each in the order corresponding to the order of the Parallel RT Beam Delimiter Boundaries (300A,0649). These are defined along the axis parallel to the motion of the delimiters of the RT Beam Limiting Device Type (300A,00B8) with respect to the Beam Modifier Coordinate System. Required if Parallel RT Beam Delimiter Opening Mode (300A,064E) has the value BINARY. Maybe be present otherwise. |
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Device that uses a fixed aperture to limit the beam. Required if Device Type Code Sequence (3010,002E) is part of CID 9545 Fixed Beam Limiting Device Types. |
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>Include Table 10.38-1 “Outline Definition Macro Attributes”. |
The Outline is defined on the Beam Modifier Definition Plane. |
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The value of Parallel RT Beam Delimiter Device Orientation Label Code Sequence (300A,0644) shall be chosen as follows:
When the value of Beam Modifier Orientation Angle (300A,0645) equals zero the code shall be (130334, DCM, "X Orientation").
When the value of Beam Modifier Orientation Angle (300A,0645) equals 90 the code shall be (130335, DCM, "Y Orientation").
When the value of Beam Modifier Orientation Angle (300A,0645) is not zero or 90, the label should be chosen to best reflect the user perception or another code may be used.
The Parallel RT Beam Delimiter Boundaries (300A,0649) shall be the positions of the mechanical boundaries (projected on the Beam Modifier Definition Plane defined by the RT Beam Modifier Definition Distance (300A,0688)) between beam delimiter elements. These are fixed for a given beam limiting device. Parallel RT Beam Delimiter Positions (300A,064A) are values specific to a given Control Point, specifying the beam limiting device element openings.
In example in Figure C.36.2.2.19.1-2 the delimiters labeled 1, 3 and 5 have a Parallel RT Beam Delimiter Leaf Mounting Side (300A,064F) value of N (negative direction) and the delimiters labeled 2 and 4 have a Parallel RT Beam Delimiter Leaf Mounting Side value of P (positive direction).
Figure C.36.2.2.19.1-3 shows the RT Beam Limiting Device Proximal Distance (300A,0642) and RT Beam Limiting Device Distal Distance (300A,0643).
In this example the reference location specified by the RT Device Distance Reference Location Code Sequence (300A,0659) has the value (130358, DCM, "Nominal Radiation Source Location").
The Referenced Defined Device Index (300A,0602) provides the facility to relate devices from one Instance to the other. Device Macros such as the RT Beam Limiting Device Definition Macro are used in Sequences which list the devices used in the context of a SOP Instance. Each device is identified by the Device Index (3010,0039). These devices may be described in other related SOP Instances. The values of Device Index (3010,0039) are not required to be the same in different SOP Instances.
For example, an RT Radiation Instance may contain the RT Beam Limiting Device Definition Sequence (300A,064D), listing the Beam Limiting Devices to be used for treatment. A related RT Radiation Record Instance for the same type of delivery device will contain the same Sequences. However, the collection of devices used may not be the same:
E.g., the RT Radiation Instance may describe a treatment that contains three Items with the following indices:
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Device Index = 1: Type (130331, DCM, "Leaf Pairs") with one leaf pair and the orientation (130334, DCM, "X Orientation"), representing X-Jaws
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Device Index = 2: Type (130331, DCM, "Leaf Pairs") with one leaf pair and the orientation (130335, DCM, "Y Orientation"), representing Y-Jaws
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Device Index = 3: Type (130331, DCM, "Leaf Pairs") with 80 leaf pairs and the orientation (130334, DCM, "X Orientation"), representing an X-MLC
However, the treatment may have been executed on a different machine which has the X-Jaws and the X-MLC, but a fixed collimator in the Y direction instead of the Y-Jaws. Therefore, the Y-Jaws will not be recorded as they have not been used. Also, the fixed collimator in Y direction is not recorded, as this is not a device which is part of the RT Beam Limiting Device Definition Sequence (300A,064D). The Referenced Defined Device Index (300A,0602) will then point to the indices in the referenced RT Radiation Instance to annotate which device in the RT Radiation Record corresponds to the device in the RT Radiation. In this case, the RT Radiation Record would contain the devices as listed in the following:
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Device Index = 1: Type (130331, DCM, "Leaf Pairs") with one leaf pair and the orientation (130334, DCM, "X Orientation"), representing X-Jaws-> Referenced Defined Device Index = 1
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Device Index = 2: Type (130331, DCM, "Leaf Pairs") with 80 leaf pairs and the orientation (130334, DCM, "X Orientation"), representing an X-MLC-> Referenced Defined Device Index = 3