Film dosimetry in water in a 23 MV therapeutic photon beam.
The field size and water depth dependence of the measured optical density of Kodak XV-2 film, irradiated in a 23 MV photon beam has been investigated. The films were positioned in a water tank in a vertical plane containing the beam axis with the upper film edge parallel to the water surface at a depth of 0.3 mm. The observed field size and water depth dependence of the film sensitivity cannot be fully attributed to the usual variation of the photon spectrum with field size and water depth: measured optical densities do significantly depend on the amount of film material above the point of measurement and on the film orientation. A method for application of film for relative water dose measurements in a plane containing the beam axis in a 23 MV therapeutic photon beam is presented; the observed agreement between film and ionisation chamber measurements is very good: typically within 1% or 2 mm.
van Battum
L J
LJ
Department of Clinical Physics, Dr. Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Heijmen
B J
BJ
D015502:Absorptiometry, Photon; D005373:Film Dosimetry / Q000295:instrumentation / Q000592:standards; D006801:Humans; D055095:Optics and Photonics; D017785:Photons; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy; D013499:Surface Properties; D014867:Water; D014962:X-Ray Film
D014867:Water