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The dose references listed in the Dose Reference Sequence (300A,0010) may receive dose contributions accumulated from different beams. Whereas the Beam Dose (300A,0084) that is used to determine the dose contribution of a beam to the Dose Reference may be calculated individually for each beam or on a fraction level carrying a nominal dose only, the accumulated dose values may also be interpreted as nominal or actual. For potential use cases, see Table C.8.8.10.3-1, for an example, and see Section C.8.8.14.7.

The Enumerated Value NOMINAL indicates that the dose value associated with the dose reference is a nominal value that was provided as an input for treatment planning. Such a value may be used to track delivered dose over a number of delivered RT Treatment Fractions in a Treatment Management System, or eventually to match against a prescribed dose value in a Hospital Information System for billing purposes.

The Enumerated Value ACTUAL indicates that the dose value associated with the dose reference was calculated during planning. Such a value may be used for quality assurance purposes where the plan parameters are used to re-calculate the dose and where a re-calculated value is expected to match the dose value provided by the Dose Reference.

The Cumulative Dose Reference Coefficient (300A,010C) is the value by which Beam Dose (300A,0084) is multiplied to obtain the dose to the referenced dose reference site at the current control point (and after previous control points have been successfully administered). The Cumulative Dose Reference Coefficient (300A,010C) is by definition zero for the initial control point. The Cumulative Dose Reference Coefficient (300A,010C) of the final control point multiplied by Beam Dose (300A,0084) results in the final dose to the referenced dose reference site for the current beam. Dose calculation for dose reference sites other than points is not well defined.

The sum of the doses of all beams calculated to the referenced dose reference may be used in different clinical scenarios, indicated by the Dose Value Purpose (300A,061D) attribute value, see Section C.8.8.10.1.

Example

In a single target case with two beams, a volume prescription of 20 Gy over 10 fractions, the single target may be represented by two Items in the Dose Reference Sequence (300A,0010): one for tracking of the dose values over the course of the delivery of a treatment plan, and one for QA purposes, where the dose value is recalculated and compared to the planned value. The first Item may therefore contain a nominal dose by a physician (e.g., 20Gy), the second Item a calculated dose at a given spatial location (e.g., 21.785Gy). The dose values are determined using the Beam Dose (300A,0084) with a Beam Dose Meaning (300A,008B) FRACTION_LEVEL (indicating that the beam dose was calculated on fraction level and carries a nominally distributed dose only).