title: Angular and radial dependence of the energy response factor for LIF-TLD micro-rods in 125L permanent implant source.
abstract: EGSnrc Monte Carlo simulations were used to calculate the angular and radial dependence of the energy response factor for LiF-thermoluminescence dosemeters (TLDs) irradiated with a commercially available (125)I permanent brachytherapy source. The LiF-TLDs were modelled as cylindrical micro-rods of length 6 mm and with diameters of 1 mm and 5 mm. The results show that for a LiF-TLD micro-rod of 1 mm diameter, the energy response relative to (60)Co gamma rays is 1.406 +/- 0.3% for a polar angle of 90 degrees and radial distance of 1.0 cm. When the diameter of the micro-rod is increased from 1 to 5 mm, the energy response decreases to 1.32 +/- 0.3% at the same point. The variation with position of the energy response factor is not >5% in a 6 cm x 6 cm x 6 cm calculation grid for the 5 mm diameter micro-rod. The results show that there is a change in the photon spectrum with angle and radial distance, which causes the variation of the energy response.
authors.affiliation: Medical Physics Division, Department of Oncology, University of Calgary and Tom Baker Cancer Center, Calgary, Alberta, Canada. pmobit@dmc.org
authors.forename: Paul
authors.initials: P
authors.lastname: Mobit
authors.forename: Iulian
authors.initials: I
authors.lastname: Badragan
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005459:Fluorides / Q000737:chemistry / Q000528:radiation effects; D007457:Iodine Radioisotopes / Q000032:analysis* / Q000627:therapeutic use*; D018499:Linear Energy Transfer; D018020:Lithium Compounds / Q000737:chemistry / Q000528:radiation effects; D008904:Miniaturization; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation* / Q000379:methods
chemical_list: D007457:Iodine Radioisotopes; D018020:Lithium Compounds; C027651:lithium fluoride; D005459:Fluorides