title: A brachytherapy photon radiation quality index Q(BT) for probe-type dosimetry.
abstract: BACKGROUND
  In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detector's response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E¯(r) must be known or another equivalent energy quality parameter used. We propose the brachytherapy photon radiation quality indexQ(BT)(E¯), to characterize the photon radiation quality in view of measurements of distributions of the absorbed dose to water, Dw, around BT sources.
  
  
  METHODS
  While the external photon beam radiotherapy (EBRT) radiation quality index Q(EBRT)(E¯)=TPR10(20)(E¯) is not applicable to BT, the authors have applied a novel energy dependent parameter, called brachytherapy photon radiation quality index, defined as Q(BT)(E¯)=Dprim(r=2cm,θ0=90°)/Dprim(r0=1cm,θ0=90°), utilizing precise primary absorbed dose data, Dprim, from source reference databases, without additional MC-calculations.
  
  
  CONCLUSIONS
  For BT photon sources used clinically, Q(BT)(E¯) enables to determine the effective mean linear attenuation coefficient μ¯(E) and thus the effective energy of the primary photons Eprim(eff)(r0,θ0) at the TG-43 reference position Pref(r0=1cm,θ0=90°), being close to the mean total photon energy E¯tot(r0,θ0). If one has calibrated detectors, published E¯tot(r) and the BT radiation quality correction factor [Formula: see text] for different BT radiation qualities Q and Q0, the detector's response can be determined and Dw(r,θ) measured in the vicinity of BT photon sources.
  
  
  CONCLUSIONS
  This novel brachytherapy photon radiation quality indexQ(BT) characterizes sufficiently accurate and precise the primary photon's penetration probability and scattering potential.
authors.affiliation: Ex-University Hospital, Radiation Oncology Dept., Clinical Radiation Physics, D 45127 Essen, Germany. Electronic address: Ulrich.Quast@uni-essen.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Quast
authors.affiliation: University-Hospital, Dept. of Radiation Oncology, Medical Physics, D 72076 Tübingen, Germany.
authors.forename: Theodor W
authors.initials: TW
authors.lastname: Kaulich
authors.affiliation: ININ, SSDL, Ionizing Radiation Metrology Department, Ocoyoacac C.P. 52750, Mexico.
authors.forename: José T
authors.initials: JT
authors.lastname: Álvarez-Romero
authors.affiliation: Radiation Physics, IMH, Linköping University, SE 58185 Linköping, Sweden; Radiotherapy Physics and Engineering, Dept. of Medical Physics, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Sa
authors.initials: S
authors.lastname: Carlsson Tedgren
authors.affiliation: Medical Physics Unit, Dept. of Oncology, McGill University, CA H3AO64, Montréal, Québec, Canada.
authors.forename: Shirin A
authors.initials: SA
authors.lastname: Enger
authors.affiliation: Dept. of Physics, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Medich
authors.affiliation: Radiation Oncology Dept., Helen F. Graham Cancer Center & Research Institute, Newark, DE 19713, USA.
authors.forename: Firas
authors.initials: F
authors.lastname: Mourtada
authors.affiliation: Radiotherapy Dept., University Hospital La Fe, 46026 Valencia, Spain and Clinica Benidorm, Alicante, Spain.
authors.forename: Jose
authors.initials: J
authors.lastname: Perez-Calatayud
authors.affiliation: Dept. of Radiation Oncology, Tufts University School of Medicine, Boston, MA 02111, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Rivard
authors.affiliation: Gummersbach Hospital, University of Cologne, Med. Rad. Physics, D 51643 Gummersbach, Germany; Dept. of Medical Physics and Biomedical Engineering, Gono University, Dhaka 1344, Bangladesh.
authors.forename: G Abu
authors.initials: GA
authors.lastname: Zakaria
mesh_terms: D001918:Brachytherapy; D017785:Photons; D011874:Radiometry / Q000379:methods*; D012542:Scattering, Radiation; D035501:Uncertainty
keywords: Absorbed dose to water; Detector response; Effective energy; Photon brachytherapy radiation quality index