title: Evaluation of a beam-spot camera for megavoltage x rays.
abstract: A beam-spot camera for measurements of x-ray focal spots of accelerators has been evaluated. The device consists of closely packed 0.25-mm-thick lead and 0.25-mm-thick cardboard strips. It is placed on radiographic film with the lamellae parallel to the beam axis and an exposure made. The images were scanned with a microdensitometer. The results indicate that the broadening of the source intensity profile at half maximum is of the order 1 mm, which permits the use of the beam-spot camera for acceptance testing and quality control. Longer tails in the density profile limit the quantitative information that can be extracted from the images.
authors.affiliation: Joint Center for Radiation Therapy, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: W R
authors.initials: WR
authors.lastname: Lutz
authors.forename: N
authors.initials: N
authors.lastname: Maleki
authors.forename: B E
authors.initials: BE
authors.lastname: Bjärngard
mesh_terms: D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D004867:Equipment Design; D006801:Humans; D010315:Particle Accelerators; D010781:Photography; D011882:Radiotherapy, High-Energy / Q000295:instrumentation* / Q000379:methods
chemical_list: D003037:Cobalt Radioisotopes