title: Quality indexes based on water measurements for low and medium energy x-ray beams: a theoretical study with PENELOPE.
abstract: OBJECTIVE
  To study the use of quality indexes based on ratios of absorbed doses in water at two different depths to characterize x-ray beams of low and medium energies.
  
  
  METHODS
  A total of 55 x-ray beam spectra were generated with the codes XCOMP5R and SPEKCALC and used as input of a series of Monte Carlo simulations performed with PENELOPE, in which the percentage depth doses in water and the kQ,Q0 factors, defined in the TRS-398 protocol, were determined for each beam. Some of these calculations were performed by simulating the ionization chamber PTW 30010.
  
  
  RESULTS
  The authors found that the relation between kQ,Q0 and the ratios of absorbed doses at two depths is almost linear. A set of ratios statistically compatible with that showing the best fit has been determined.
  
  
  CONCLUSIONS
  The results of this study point out which of these ratios of absorbed doses in water could be used to better characterize x-ray beams of low and medium energies.
authors.affiliation: Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain and FISRAD S.A.S Carrera 64 a No 22-41, Bogotá D.C., Colombia.
authors.forename: U
authors.initials: U
authors.lastname: Chica
authors.affiliation: Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Anguiano
authors.affiliation: Servicio de Radiofísica, Hospital Universitario "San Cecilio", Avda. Dr. Olóriz, 16, E-18012 Granada, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Vilches
authors.affiliation: Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain.
authors.forename: A M
authors.initials: AM
authors.lastname: Lallena
mesh_terms: D009010:Monte Carlo Method; D014867:Water; D014965:X-Rays
chemical_list: D014867:Water