title: Influence of field size on a PTW type 23342 plane-parallel ionization chamber's response.
abstract: The response of a PTW type 23342 plane-parallel ionization chamber, both in air and in phantom, was evaluated for x-ray tube potentials between 30 and 100 kV and radiation field diameters ranging from 30 to 70 mm. The experiments were performed with a calibrated Pantak x-ray machine and made use of the same set of x-ray qualities adopted by the PTB primary laboratory for the calibration of such chambers. A Plexiglas phantom (1.18 g cm(-3)) 110 mm long, 110 mm wide, and 80 mm deep was used for phantom measurements. X-ray qualities were characterized by using 99.99% pure aluminum filters. On the basis of the IAEA's TRS 398, the article discusses the dependence of the plane-parallel ionization chamber readings with field size in air and in phantom, its implication with regard to clinical dosimetry, cross-calibration, and dissemination of calibration factors.
authors.affiliation: Centro Regional de Ciências Nucleares da CNEN, Rua Cônego Barata, 999, Recife, PE Brazil 52110-120. auster@elogica.com.br
authors.forename: C
authors.initials: C
authors.lastname: Austerlitz
authors.forename: H P
authors.initials: HP
authors.lastname: Villar
authors.forename: M A P
authors.initials: MA
authors.lastname: Santos
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity