DICOM PS3.3 2021e - Information Object Definitions

7.14 Extension of The DICOM Model of The Real-world for Radiotherapy Second Generation Information Objects

For the purpose of RT Second Generation SOP Classes the DICOM Model of the Real-World is described in this section. This subset of the real-world model covers the requirements for transferring information about planned and performed radiotherapeutic treatments and associated data.

Figure 7.14-1 describes the most important elements involved in the radiotherapy domain in DICOM.

DICOM Model of the Real World - Radiotherapy

Figure 7.14-1. DICOM Model of the Real World - Radiotherapy


  1. IODs which contain a representation of Volumes, Surfaces, Lines, Points can be annotated by an RT Segment Annotation.

  2. For better readability the diagram only contains the most important relationships, e.g. all objects have a relation to the Patient, but not all of these relationships are part of this diagram.

7.14.1 RT Course

The RT Course is a top-level entity that represents a radiotherapy treatment course, usually specified in one or more RT Prescriptions, generally for a defined tumor or group of tumors. A patient undergoing treatments of radiotherapy has one treatment course at a time. The RT Course may consist of several RT Treatment Phases (possibly with breaks of treatment in between them). Each treatment phase may consist of one or more RT Treatment Sessions. An RT Treatment Session is delivered in one patient visit to a venue with a treatment machine and will typically deliver a fraction of one or more RT Radiation Sets. A new RT Course is administered, when the patient is treated for a re-occurrence or a new tumor site - typically after a period of a year or more after the previous RT Course has been finished.

The RT Course can be thought of as a container collecting all major objects which are relevant to this course. The RT Physician Intent and RT Radiation Sets reference other companion objects necessary to prepare, conduct and review the treatment. Timing information (start dates and phasing of treatment, breaks etc.) are also part of the RT Course information. Additionally it contains information of the ongoing status in treatment planning and delivery. The RT Course is a dynamic object that represents the current status of the patient"s treatment.

The RT Course may also include information about previously conducted treatments by referencing previous RT Course objects or by directly recording the information in Attributes.

DICOM PS3.3 2021e - Information Object Definitions