The correct archetype to use for radiotherapy contouring and planning

Hello, our group has been discussing what is the correct archetype to describe the completed action of radiotherapy contouring (the process of delineating organs and other structures on radiological images for dose delivery and avoidance purposes) and treatment planning.

Specifically, we have been interested in whether the openEHR-EHR-ACTION.procedure.v1 archetype is the correct one to record information on what structures were contoured and by whom.

Arguments in favor:

  • The Purpose section of that archetype specifically mentions planning as one of the accepted uses cases. Contouring and treatment planning definitely fall into that category.
  • SNOMED CT defines the following codes in its procedures valueset: 31344000 : Radiation therapy treatment planning, patient contour and localization of internal structures, 9990009 : Radiation therapy treatment planning service, 52338008 : Treatment planning for brachytherapy

Arguments against:
Maybe the openEHR-EHR-ACTION.procedure.v1 is reserved for the procedures you do directly on the patient, with the requirement being that they are present during the procedure.

As experts, what do you guys think? Can we go with this or should we create a new ACTION-based archetype? There are not a lot of radiology and radiotherapy-based archetypes in the CKM.

Thanks in advance for your help.


Hi Matija,

If you search for ‘radiation’ you will find that there are a few other similar questions. For those of us who are not specialists in this world, it can be difficult to understand the bigger picture.

‘Contouring’ sound s much more like the planning/ordering phase to perhaps an INSTRUCTION.service_request with a custom radiotherapy contouring cluster, or arguably a specific Radiation therapy ‘order’ archetype.

I imagine that, similar to medication there is a need to mirror, what was originally planned vs. what was actually delivered.

A wee mindmap or outline of the overall radiation therapy process would be very helpful.


I think the ‘planning’ referred to in the Procedure metadata really refers to capturing that the procedure is in a ‘being planned’ state , rather than capturing the plan itself.

Hey Ian,

thanks for the answers. I will try to explain the concepts a bit more thoroughly, but please keep in mind that I am of course not a clinical expert, but just a lowly CS guy and someone who is fairly new to radiotherapy application development myself.

  1. After the diagnosis, the radiation oncologist will create a prescription (sometimes call intent) for irradiation. This will include the total dose delivered to the patient’s body and the number of fractions (irradiation sessions to deliver them in), i.e, deliver 5 x 250 cGy (centigrays) of radiation to the body.

  2. Next, a more detailed specification of the body regions that receive the irradiation needs to be created. This is done that in the contouring part of the Treatment Planning System, which is a kind of 3D Photoshop working on CT (or MRI, PET etc. or a combination of these) images to delineate organs and regions that need to be irradiated (or avoided). The first rough sketch of this is usually also done by the radiation oncologist, but often to create fully detailed 3D structures, the medical physicist takes over, possibly assisted by some AI algorithms. The result is 3D volumes (structures) describing these irradiation regions. This process is called contouring and this what we want to describe with the openEHR-EHR-ACTION.procedure.v1 archetype (or some other archetype), although more in the metadata fashion (the names and the IDs of the structures created, who created them and when) - the actual volumes themselves are not stored in the data instance.

  3. After that, the actual machine instructions need to be configured, i.e., the number of beams used for irradiation, their angles, the dose they deliver etc… Depending on planning modality (CRT, IMRT, VMAT etc.), the dose can be configured either manually (which I gather is rarely done nowadays) or else some constraints are specified (this structure may receive at most 70 cGy of irradiation, this structure must receive at least 50 cGy, this structure must be completely avoided etc.) and have the Treatment Planning System calculate actual dose delivered, beam parameters etc. . The plan goes through several optimization cycles, led by the medical physicist and finally approved by the radiation oncologist. This process is called treatment planning and is also something we would like to describe with the procedure or similar archetype in a similar metadata fashion.

  4. Now we’re more or less ready for irradiation.

Now this is a fairly rough overview of what the entire preparation cycle looks like. The difficulty in choosing what the correct archetype is to describe these preparatory/planning actions lies in the fact that they are complex and long-lasting actions that are not performed directly on the patient, but essentially on their radiological images and that this data is often used by many different applications that are part of the oncology department’s IT stack even before or without the patient being irradiated.