Equipment Frame of Reference UID Attribute
| Tag | (300A,0675) |
|---|---|
| Type | Required (1) |
| Keyword | EquipmentFrameOfReferenceUID |
| Value Multiplicity | 1 |
| Value Representation | Unique Identifier (UI) |
Frame of Reference identifier identifying the Equipment Frame of Reference coordinate system which is the parent for Imaging Source Coordinate System and/or the Image Receptor Coordinate System.
See Section 10.39.1.1, Section C.36.1.1.11 and Section C.36.1.1.12.
Section 10.39.1.1
10.39.1.1 Equipment Coordinate System
A piece of equipment has an Equipment Coordinate System which can be used for expressing geometric concepts such as locations and orientations. The coordinate system is characterized by the location of the origin and the orientation of coordinate axes with respect to the equipment. The Equipment Coordinate System is a right-handed coordinate system.
Equipment Coordinate Systems are typically based on a standardized definition of axes. The choice of origin is often device-specific or device-type-specific. It may be any significant location on the machine such as the manufacturer-dependent machine isocenter.
The Equipment Coordinate System can be used as the parent for derived coordinate systems.
Section C.36.1.1.11
C.36.1.1.11 Imaging Source Coordinate System
TheImaging Source Coordinate System describes the location of the imaging source with respect to the Equipment Frame of Reference coordinate system identified by the Equipment Frame of Reference UID (300A,0675) , i.e. the Equipment Frame of Reference coordinate system is the parent system of the Imaging Source Coordinate System.
The Device Position to Equipment Mapping Matrix (3002,010F) relates the two coordinate systems, and when it is identity:
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The origin of Imaging Source Coordinate System is located at the origin of the Equipment Frame of Reference coordinate system
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The axes of Imaging Source Coordinate System are aligned with the axes of the Equipment Frame of Reference coordinate system
The Imaging Source Coordinate System is aligned with the imaging source as follows:
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The origin of the Imaging Source Coordinate System is the nominal location of the imaging source.
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The z-axis is aligned with the central ray of the diverging rays of the imaging source
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The positive z-axis is in the direction from the image receptor to the imaging source
Beam modifying devices attached to the imaging source, such as Beam Limiting Devices, use a Base Beam Modifier Coordinate System, if they use coordinates in their specification.
The Base Beam Modifier Coordinate System, defined in Section C.36.1.1.9 Beam Modifier Coordinate System, is related to the Image Source Coordinate System as follows:
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The parent system of theBase Beam Modifier Coordinate Systemis the Imaging Source Coordinate System.
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The Base Beam Modifier Plane is located at a distance specified by RT Beam Modifier Definition Distance (300A,0688) along the z-axis from the reference location specified by RT Device Distance Reference Location Code Sequence (300A,0659).
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If the radiation used for imaging is generated by an imaging-specific source, the RT Device Distance Reference Location Code Sequence (300A,0659) shall have the value (130789, DCM, "Nominal Imaging Source Location")
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If the radiation used for imaging is generated by the therapeutic source ("MV Imaging") , the RT Device Distance Reference Location Code Sequence (300A,0659) shall have the value (130358, DCM, "Nominal Radiation Source Location")
Section C.36.1.1.12
C.36.1.1.12 Image Receptor Coordinate System
The Image Receptor Coordinate System describes the location of the image acquisition receptor device with respect to the Equipment Frame of Reference coordinate system identified by the Equipment Frame of Reference UID (300A,0675) , i.e. the Equipment Frame of Reference coordinate system is the parent system of the Image Receptor Coordinate System.
The Image Receptor Coordinate System is also used when describing the location of an acquisition plane of a virtual imaging device without presence of physical image receptor, e.g. in case of a digital reconstructed radiograph (DRR).
The Pixel Spacing (0028,0030) is measured on the x/y plane of the Image Receptor Coordinate System at z = 0.
The Device Position to Equipment Mapping Matrix (3002,010F) relates the two coordinate systems, and when it is identity:
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The origin of Image Receptor Coordinate System is located at the origin of the Equipment Frame of Reference coordinate system
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The axes of Image Receptor Coordinate System are aligned with the axes of the Equipment Frame of Reference coordinate system
The Image Receptor Coordinate System is aligned with the image receptor as follows.
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The z-axis passes through the center of the image receptor
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For rectangular receptors, the x-axis and y-axis are aligned with the edges of the image receptor.
The alignment shall be documented in the Conformance Statement for the device.