Relating two techniques for handling uncertainties in IMRT optimization.

Radiotherapy treatment planning is associated with uncertainties. Examples are uncertainties in the tumour location due to organ movement or the inter/intra observer variability in target definition. Different approaches to incorporate uncertainties into IMRT optimization have been proposed. In this note, we point out a relation between two previously published methods: the coverage probability approach and the concept of optimizing the expectation value of an objective function that depends on a set of random variables. Both concepts are generally different, but turn out to be equivalent in special cases.