title: An alternative beam quality index for medium-energy x-ray dosimetry.
abstract: To determine absorbed dose to water it is essential that the radiation quality of the x-ray beam is known accurately. The unique method of defining the beam quality is to acquire a detailed knowledge of the photon spectrum at the point of measurement in water, but this is impractical. The aim of this work was to investigate a quality index that uniquely defines the ratio of mass-energy absorption coefficients of water to air at 2 cm deep in water ([(mu en/rho)w/a]z = 2,phi). Three parameters, HVL, mean energy at 2 cm deep in water and the ratio of the doses at 2 and 5 cm deep in water (D2/D5) were investigated as functions of [(mu en/rho)w/a]z = 2,phi. The quality index that best defines [(mu en/rho)w/a]z = 2,phi is the ratio of doses at 2 and 5 cm depth in water.
authors.affiliation: National Physical Laboratory, Teddington, Middlesex, UK.
authors.forename: K E
authors.initials: KE
authors.lastname: Rosser
mesh_terms: D000388:Air; D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D017785:Photons / Q000627:therapeutic use; D011786:Quality Control; D011874:Radiometry / Q000592:standards / Q000706:statistics & numerical data*; D011880:Radiotherapy Planning, Computer-Assisted / Q000592:standards / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires; D006113:United Kingdom; D014867:Water
chemical_list: D014867:Water