DICOM PS3.3 2018a - Information Object Definitions

C.8.8.15.16 Geometric Parameters
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##### C.8.8.15.16 Geometric Parameters

A Channel is the combination of the Transfer Tube and the Source Applicator. A Channel is physically connected to one of the connection sockets of the afterloader. Afterloader Channel ID (300A,0273) unambiguously identifies the afterloader channel to which the applicator is connected; see Section C.8.8.15.16.2. Both Afterloader Channel ID (300A,0273) and Source Applicator ID (300A,0291) describe the connection between the afterloader and the applicator (so called channel mapping). Channel Number (300A,0282) is used to index the items within the Channel Sequence (300A,0280) and does not serve as the identification of the channel socket at the afterloader.

Figure C.8.8.15-1. RT Brachy Channel Geometric Parameters

### Note

Channel Length (300A,0284) has been interpreted in different ways. Channel Effective Length (300A,0271) should be used instead, as the distance from the afterloader to the center of the distal-most possible dwell position following the definition in Figure C.8.8.15-1.

Additionally, the Transfer Tube Length (300A,02A4) may be specified. If Transfer Tube Length (300A,02A4) is absent or has no value, the distance from the Source Applicator connector to the center of the distal-most possible dwell position is equal to the value of the Channel Effective Length (300A,0271). If Transfer Tube Length (300A,02A4) has a value, the distance from the Source Applicator connector to the center of the distal-most possible dwell position is equal to the Channel Effective Length (300A,0271) minus the Transfer Tube Length (300A,02A4). The concept of Source Applicator Length (300A,0296) should not be used any longer.

###### C.8.8.15.16.1 Channel Inner Length

The Channel Inner Length (300A,0272) is the measurable physical inner length of the channel. It specifies the distance between the connector on the afterloader and the inner end of the channel. In the RT Brachy Session Record Module it shall be specified as the measured or verified length.

###### C.8.8.15.16.2 Afterloader Channel ID

The Afterloader Channel ID (300A,0273) is the connector socket identification on the afterloader where the channel is connected.

Figure C.8.8.15-2. RT Brachy Channel and Applicator IDs

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DICOM PS3.3 2018a - Information Object Definitions