A.18 RT Dose IOD
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## A.18 RT Dose IOD

### A.18.1 RT Dose IOD Description

The focus for this Radiotherapy Dose IOD (RT Dose IOD) is to address the requirements for transfer of dose distributions calculated by radiotherapy treatment planning systems. These distributions may be represented as 2D or 3D grids, as isodose curves, or as named or unnamed dose points scattered throughout the volume. This IOD may also contain dose-volume histogram data, single or multi-frame overlays and application-defined lookup tables. This IOD does not provide for definition of doses in beam or other coordinate systems. The application is responsible for transforming data in other, non-patient based coordinate systems to the patient based coordinate system described in Section C.7.6.2.1.1.

### A.18.2 RT Dose IOD Entity-Relationship Model

The E-R model for the RT Dose IOD is illustrated in Figure A.18-1.

Figure A.18-1. DICOM RT Dose IOD Information Model

### A.18.3 RT Dose IOD Module Table

Table A.18.3-1. RT Dose IOD Modules

IE | Module | Reference | Usage
--- | --- | --- | ---
Patient | Patient | C.7.1.1 | M
Clinical Trial Subject | C.7.1.3 | U
Study | General Study | C.7.2.1 | M
Patient Study | C.7.2.2 | U
Clinical Trial Study | C.7.2.3 | U
Series | RT Series | C.8.8.1 | M
Clinical Trial Series | C.7.3.2 | U
Frame of Reference | Frame of Reference | C.7.4.1 | M
Equipment | General Equipment | C.7.5.1 | M
Dose | General Image | C.7.6.1 | C - Required if dose data contains grid-based doses.
Image Plane | C.7.6.2 | C - Required if dose data contains grid-based doses.
Image Pixel | C.7.6.3 | C - Required if dose data contains grid-based doses.
Multi-frame | C.7.6.6 | C - Required if dose data contains grid-based doses and pixel data is multi-frame data.
Overlay Plane | C.9.2 | U
Multi-frame Overlay | C.9.3 | U
Modality LUT | C.11.1 | U
RT Dose | C.8.8.3 | M
RT DVH | C.8.8.4 | U
Structure Set | C.8.8.5 | C - Required if dose data contains dose points or isodose curves
ROI Contour | C.8.8.6 | C - Required if dose data contains dose points or isodose curves
RT Dose ROI | C.8.8.7 | C - Required if dose data contains dose points or isodose curves
SOP Common | C.12.1 | M
Common Instance Reference | C.12.2 | U
Frame Extraction | C.12.3 | C - Required if the SOP Instance was created in response to a Frame-Level retrieve request

### Note

1. Within the RT Dose IOD, the RT Dose module supports 2D and 3D dose grids. The Structure Set, ROI Contour and RT Dose ROI modules together support isodose curves and points, and the RT DVH module supports dose-volume histogram data. They are not mutually exclusive: all four representations may be included in a single instance of the object or they may be included in any combination. Product Conformance Statements should clearly state which of these mechanisms is supported and under what conditions.

2. The RT Dose IOD has been defined as a composite IOD, separate from the RT Plan IOD. This has been done for the following reasons:

   - to allow for the multiplicity of possible dose calculations using beam models for the same basic plan,

   - to avoid undesirable transmission of large amounts of data with the treatment plan, and

   - to accommodate the fact that CT Simulation and other "beam geometry" generating devices that use the RT Plan IOD do not have or require access to this data, either for transmission or storage.

3. The Audio Module was previously included in this IOD but has been retired. See PS3.3-2004.

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