A control circuit provides a user with an opportunity to designate one or more patient structures for a particular patient that are to be protected from radiation. When optimizing a radiation-treatment plan for that patient, then, the control circuit uses the designated patient structure(s) as an area to be masked from radiation during administration of the radiation-treatment plan. By one approach the aforementioned opportunity to designate patient structures as being designated patient structures comprises providing the user with an opportunity to so designate patient structures via a display. The aforementioned masking can be accomplished as desired including by appropriate use of a multi-leaf collimator.