title: Analysis of post-exposure density growth in radiochromic film with respect to the radiation dose.
abstract: The post-exposure density growth (PEDG) is one of the characteristics of radiochromic film (RCF). In film dosimetry using RCF and a flatbed scanner, pixel values read out from the RCF are converted to dose (hereafter, film dose) by using a calibration curve. The aim of this study is to analyze the relationship between the pixel value read out from the RCF and the PEDG, and that between the film dose converted from the RCF and the PEDG. The film (GAFCHROMIC EBT) was irradiated with 10-MV X-rays in an ascending 11-dose-step arrangement. The pixel values of the irradiated EBT film were measured at arbitrary hours using an Epson flatbed scanner. In this study, the reference time was 24 h after irradiation, and all dose conversions from the pixel values read out from the EBT film were made using a calibration curve for 24 h after irradiation. For delivered doses of 33 and 348 cGy, the measured pixel values at 0.1 and 16 h after irradiation represented ranges of -9.6% to -0.7% and -3.9% to -0.3%, respectively, of the reference value. The relative changes between the pixel values read out from the EBT film at each elapsed time and that at the reference time decreased with increasing delivered dose. However, the difference range for all the film doses had a width of approximately -10% of the reference value at elapsed times from 0.1 to 16 h, and it showed no dependence on the delivered dose.
authors.affiliation: Department of Radiation Oncology and Medical Physics, Graduate School of Medicine, Sapporo Medical University, Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Shima
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tateoka
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Saitoh
authors.forename: Junji
authors.initials: J
authors.lastname: Suzuki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yaegashi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Takuya
authors.initials: T
authors.lastname: Nakazawa
authors.forename: Akihiro
authors.initials: A
authors.lastname: Nakata
authors.forename: Tadanori
authors.initials: T
authors.lastname: Abe
authors.forename: Sho
authors.initials: S
authors.lastname: Imai
authors.forename: Kouichi
authors.initials: K
authors.lastname: Sakata
authors.forename: Masato
authors.initials: M
authors.lastname: Hareyama
mesh_terms: D016477:Artifacts; D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity