Methods described herein include selecting a target disease having an associated therapeutic dose of radiation, determining a maximal energy in an x-ray radiation beam to be emitted from a radiotherapy system to deliver a therapeutic dose of radiation associated with the target disease to target tissue in a patient, the selected disease of the plurality of diseases requiring differing maximal energies of the x-ray radiation beam to achieve the associated therapeutic dose of radiation than the maximal energy required to achieve the associated therapeutic dose of radiation for another disease, and outputting to an output module an indication of the determined maximal energy. Methods carried out in a system that can include a processing module that receives an input including a selection of a target disease, and an output module, coupled to the processing module, that outputs, an indication of the determined maximal energy.