title: Experimental determination of the Task Group-43 dosimetric parameters of the new I25.S17plus (125)I brachytherapy source.
abstract: OBJECTIVE
  To present experimental dosimetry results for the new IsoSeed I25.S17plus (125)I brachytherapy source, in fulfillment of the American Association of Physicists in Medicine recommendation for, at least one, experimental dosimetry characterization of new low-energy seeds before their clinical implementation.
  
  
  METHODS
  A batch of 100 LiF thermoluminescent dosimeter (TLD)-100 microcubes was used for the experimental determination of the dose-rate constant, radial dose, and anisotropy functions, in irradiations performed using two Solid Water phantoms. Monte Carlo (MC) simulations were used to determine appropriate correction factors that account for the use of Solid Water as a phantom material instead of liquid water and for the different energy response of the TLD dosimeters in the experimental (125)I photon energies relative to the 6 MV x-ray photon beam used for the TLD calibration. Measurements were performed for four I25.S17plus seeds; one with direct traceability of air-kerma strength calibration to National Institute of Standards and Technology and three with secondary National Institute of Standards and Technology traceability.
  
  
  RESULTS
  A mean dose-rate constant, Λ, of 0.956 ± 0.043 cGy h(-1) U(-1) was experimentally determined for the I25.S17plus source, which agrees within uncertainties with the MC result of 0.925 ± 0.013 cGy h(-1) U(-1) calculated independently for the same seed model in a previous study. Agreement was also observed between the measured and the MC-calculated radial dose and anisotropy function values.
  
  
  CONCLUSIONS
  Experimental dosimetry results for the I25.S17plus (125)I source verify corresponding independent MC results in the form of Task Group-43 dosimetry parameters. The latter are found in agreement within uncertainties with sources of similar design incorporating a silver marker, such as the Oncura OncoSeed Model 6711.
authors.affiliation: Medical Physics Laboratory, Medical School, University of Athens, Athens, Greece.
authors.forename: Argyris
authors.initials: A
authors.lastname: Moutsatsos
authors.affiliation: Medical Physics Laboratory, Medical School, University of Athens, Athens, Greece.
authors.forename: Evaggelos
authors.initials: E
authors.lastname: Pantelis
authors.affiliation: Medical Physics Laboratory, Medical School, University of Athens, Athens, Greece. Electronic address: ppapagi@med.uoa.gr.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Papagiannis
authors.affiliation: Department of Medical Physics & Engineering, Sana Klinikum, Offenbach, Germany.
authors.forename: Dimos
authors.initials: D
authors.lastname: Baltas
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D002138:Calibration; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008954:Models, Biological; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011874:Radiometry / Q000379:methods; D013819:Thermoluminescent Dosimetry
chemical_list: D007457:Iodine Radioisotopes
keywords: (125)I seed; Dosimetry; TLD; Task Group 43