A control circuit optimizes a brachytherapy radiation treatment plan for a patient target volume by defining a radiation-control structure that conformally surrounds the patient target volume and then automatically removes part, but not all, of the radiation-control structure to control consideration of radiation sources that are not disposed within the patient target volume. By one approach the control circuit selectively removes parts of the radiation-control structure as a function of the geometry as corresponds to placement of one or more of the radiation sources. For many application settings it serves well for the radiation-control structure to represent a radiation-avoidance area.
