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Influence of field size on a PTW type 23342 plane‐parallel ionization chamber's response
Author(s) -
Austerlitz C.,
Villar H. P.,
Santos M. A. P.
Publication year - 2004
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1819554
Subject(s) - imaging phantom , ionization chamber , dosimetry , calibration , ionization , optics , materials science , physics , nuclear medicine , medicine , ion , quantum mechanics
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 and100 kVand radiation field diameters ranging from 30 to70 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 gcm − 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.