title: Polarity correction factor for flattening filter free photon beams in several cylindrical ionization chambers.
abstract: In this study, we aimed to compare the polarity correction factor in ionization chambers for flattening filter free (FFF) photon beams and flattening filter (FF) beams. Measurements were performed with both 6 and 10 MV FFF and FF beams. Five commercial ionization chambers were evaluated: PTW TN30013; IBA Dosimetry CC01, CC04, and CC13; and Exradin A12S. Except for the CC01 ionization chamber, the other four chambers showed less than a 0.3 % difference in the polarity effect between the FFF and the FF beams. The CC01 chamber showed a strong field-size-dependence, unlike the other chambers. The polarity effect for all chambers with FFF beams did not change with the dose rate. Except in the case of the CC01 chamber, the difference in the polarity effect between FFF and FF beams was not significant.
authors.affiliation: Division of Medical Technology Support, Kobe Minimally Invasive Cancer Center, 8-5-1, Minatojima-nakamachi, Chuo-ku, Kobe, 650-0046, Japan. ogata@k-mcc.net.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ogata
authors.affiliation: Division of Medical Technology Support, Kobe Minimally Invasive Cancer Center, 8-5-1, Minatojima-nakamachi, Chuo-ku, Kobe, 650-0046, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Uehara
authors.affiliation: Division of Medical Technology Support, Kobe Minimally Invasive Cancer Center, 8-5-1, Minatojima-nakamachi, Chuo-ku, Kobe, 650-0046, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Nakayama
authors.affiliation: Division of Medical Technology Support, Kobe Minimally Invasive Cancer Center, 8-5-1, Minatojima-nakamachi, Chuo-ku, Kobe, 650-0046, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Tsudou
authors.affiliation: Division of Medical Technology Support, Kobe Minimally Invasive Cancer Center, 8-5-1, Minatojima-nakamachi, Chuo-ku, Kobe, 650-0046, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Masutani
authors.affiliation: Division of Medical Technology Support, Kobe Minimally Invasive Cancer Center, 8-5-1, Minatojima-nakamachi, Chuo-ku, Kobe, 650-0046, Japan.
authors.forename: Takanobu
authors.initials: T
authors.lastname: Okayama
mesh_terms: D017785:Photons; D011874:Radiometry / Q000295:instrumentation*
keywords: Flattening filter free (FFF); Ionization chamber; Polarity effect