Variations in the beam characteristics of the Varian Clinac-4 (Pb).
D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy; D010315:Particle Accelerators; D055585:Physical Phenomena; D010825:Physics; D011874:Radiometry / Q000295:instrumentation; D011879:Radiotherapy Dosage; D013679:Technology, Radiologic