Webster defines the word “dose” as “the measured quantity of medicine to be taken at one time or in a given period of time; a definite quantity or portion, usually small, of anything regarded as having a remedial or beneficial influence.” “Dosage” is defined as “the administration of medicine in doses, especially in graded doses, according to age, etc.“ Years of usage have confirmed a definite concept associated with these words. An ounce of castor oil may confidently be expected, with minor variations, to produce a definite result. Five or ten grains of aspirin may be relied upon to relieve certain symptoms. These medications are measured in simple units which are related to the effect. The pharmacological action of moot drugs in common use is well understood. With radiation therapy, these conditions do not apply. Yet the terms “dose” and “dosage” are used analogously, referring to an amount of radiant energy directed at the patient in a period of time, with the object of palliation or even with the hope...