Treatment Course Session Number

**Semantic type:** Quantitative Concept

**Definition:** The number of a treatment course session. A session is defined as the period of time between when the patient enters the treatment room and when they leave it. If the session is interrupted, for example if the machine goes down or the patient has to leave the treatment room to use the restroom, then the session whole number is retained and decimal values are used to indicate the sub-sessions when the patient returns to the treatment room. Decimal increments are zero-based so session 1 and session 1.0 are identical. Sessions 1.0 and 1.1 would indicate that the entire dose intended for delivery in session 1 had to be broken up into two sub-sessions 1.0 and 1.1. Similarly, if delivery of the total dose intended for a session is broken up between two machines e.g., half for the day on a photon machine and half for the day on a hadron machine, then this would also be reflected in the two sub sessions 1.0 and 1.1.

**Synonyms:** - Session Number In Course