title: Experimental evaluation of conversion factors, N(D,w)/N(X), for Roos-type and Advanced-Markus-type plane-parallel ionization chambers.
abstract: A Japanese code of practice for clinical dosimetry, titled "Standard Dosimetry of Absorbed Dose in External Beam Radiotherapy" was published by the Japan Society of Medical Physics (JSMP) in 2002. It mostly followed IAEA Technical Reports Series No. 398, which was based on N(D,w), i.e., the calibration factor in terms of absorbed dose to water for a dosimeter. The Japanese primary standard dosimetry laboratory, however, has not supplied N(D,w) but N(X), as the calibration factor in terms of exposure. The unique feature of the Japanese code was provision of a data table of calculated conversion factors, N(D,w) / N(X) values, for many types of ionization chambers, excluding new plane-parallel ionization chambers. This paper describes the experimental evaluation of the conversion factors for the new plane-parallel ionization chambers, such as the Roos-type and Advanced Markus chambers. The obtained N(D,w) / N(X) values for PTW 34001, Wellhöfer PPC 40 and PTW 34045 were 37.96 +/- 0.19, 37.85 +/- 0.36 and 37.90 +/- 0.26 (Gy/C kg(-1)), respectively. They agreed with estimations based on Monte Carlo calculations.
authors.affiliation: National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba-shi, 263-8555, Japan. fukumura@nirs.go.jp.
authors.forename: Akifumi
authors.initials: A
authors.lastname: Fukumura
authors.forename: Masahiro
authors.initials: M
authors.lastname: Endo
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Kanai
authors.forename: Mitsue
authors.initials: M
authors.lastname: Takeshita
authors.forename: Makoto
authors.initials: M
authors.lastname: Sakama
authors.forename: Akira
authors.initials: A
authors.lastname: Ito
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Masao
authors.initials: M
authors.lastname: Hoshina
authors.forename: Yohsuke
authors.initials: Y
authors.lastname: Kusano
authors.forename: Eisuke
authors.initials: E
authors.lastname: Takase
authors.forename: Jayantha
authors.initials: J
authors.lastname: Gunaratne
mesh_terms: D002138:Calibration; D004583:Electrons; D007564:Japan; D009010:Monte Carlo Method; D011874:Radiometry; D014867:Water
chemical_list: D014867:Water