The Enhanced RDSR provides a complete geometric description of all equipment components, which allows more accurate understanding of dose distribution and potential patient impact in dosimetry analysis.
This geometric description defines one single RDSR Reference Coordinate System (referred to as the RDSR RCS) and all equipment components are described in that RCS. A second Reference Coordinate System is defined for the X-Ray Source (referred to as the Source RCS), and its origin and orientation are defined with respect to the RDSR RCS.
Some equipment components, such as patient support, which do not move with the X-Ray Source are described using the RDSR RCS. Other equipment components, such as collimators and X-Ray filters, which move with the X-Ray Source are described using the Source RCS.
The TID 10043 “Irradiation Details” encodes the RDSR RCS as the RDSR Frame of Reference Origin and the Frame of Reference UID. The origin of this RCS is defined by the equipment manufacturer, and can be either a point fixed in the room, or a point fixed on one of the equipment components that is not directly attached to a moving X-Ray Source, such as the patient support, the Isocenter, or the patient (refer to CID 10074). For example, the origin of the RDSR RCS is not recommended to be the X-Ray Source itself, the X-Ray Filter, or the Output Measurement Point.
There are components of the equipment that are described in the RDSR RCS:
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X-Ray Source RCS. The TID 10050 “X-Ray Source Reference Coordinate System” defines the position and orientation of the X-Ray Source RCS with respect to the RDSR RCS with a transformation matrix. Two mechanisms might be used:
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The TID 10044 “Radiation Source Characteristics” describes the inherent filtration, focal spot size, anode material, etc. The TID 10045 “Radiation Technique” describes the X-Ray techniques applied, such as kVp, pulse width, half value layer, etc.
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Attenuators that are not directly attached to the X-Ray Source, such as Patient Support, Compression Paddle etc. Their positions are encoded in TID 10052 “Attenuator Position” as references to 3D data models along with a transformation matrix between the RCS of these 3D models and the RDSR RCS.
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The TID 10047 “Attenuators” includes the TID 10055 “Attenuator Characteristics” that describes their characteristics such as material and thickness.
There are other components of the equipment that are described in the X-Ray Source RCS:
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Filters: The TID 10051 “Beam Position” defines the position of the attenuators that are attached to the X-Ray Source, such as X-Ray Filters and Contour Filters. They are encoded as references to 3D data models along with a transformation matrix between the RCS of these 3D models and the X-Ray Source RCS.
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X-Ray Filters are described in TID 10046 “Filtration”, and their characteristics are described in the TID 10055 “Attenuator Characteristics”
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Dose Reference Points: The TID 10051 “Beam Position” also defines the Reference Point Position and the Output Measurement Point Position. Note that the Reference Point RP Definition is provided in TID 10041 and the iAK at Point RP is provided in TID 10048.
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Collimator: The TID 10049 “Radiation Field Area” defines the position of the collimator, encoded as a shape of 3D points in the X-Ray Source RCS.
Figure UUUU.4.5.4.1-1 provides further details of the system components in the RDSR and the X-Ray Source Coordinate Systems.
The Enhanced RDSR includes a transformation matrix to relate the Source RCS (which may move) to the RDSR RCS. Equipment components described in the Source RCS are fixed within this coordinate system. When the X-Ray Source moves with respect to the RDSR RCS, the X-Ray Source Transformation Matrix describes the movement of the X-Ray Source components in the RDSR RCS. Figure UUUU.4.1.1.1-1 shows the relationship between the RDSR RCS and the Source RCS.
