A system and method of radiation planning. The system and method are configured to implement or include the steps of (a) obtaining an image of a patient encompassing tumorous and non-tumorous tissue, (b) applying an encompassing field to the image having an area covering the tumorous and non-tumorous tissue, (c) using a graphical user interface to subtract subset fields from the encompassing field corresponding to radiation sensitive non-tumorous tissues to define a treatment area, and (d) inputting the treatment area to a computer program to generate a radiation treatment plan based on at least one prescribed dose to the treatment area.