The present embodiments relate to producing a radiation treatment plan. In one embodiment, the method may include specifying a dataset in which an object requiring to be irradiated is represented; determining a target volume requiring to be irradiated within the object; ascertaining a metric identifying a density heterogeneity for a region that will be struck by the planned treatment beam; and determining as a function of the ascertained metric a safety margin for the target volume requiring to be irradiated.