title: An investigation into the accuracy of Acuros(TM) BV in heterogeneous phantoms for a (192)Ir HDR source using LiF TLDs.
abstract: The aim of this study was to evaluate the accuracy of the new Acuros(TM) BV algorithm using well characterized LiF:Mg,Ti TLD 100 in heterogeneous phantoms. TLDs were calibrated using an (192)Ir source and the AAPM TG-43 calculated dose. The Tölli and Johansson Large Cavity principle and Modified Bragg Gray principle methods confirm the dose calculated by TG-43 at a distance of 5 cm from the source to within 4 %. These calibrated TLDs were used to measure the dose in heterogeneous phantoms containing air, stainless steel, bone and titanium. The TLD results were compared with the AAPM TG-43 calculated dose and the Acuros calculated dose. Previous studies by other authors have shown a change in TLD response with depth when irradiated with an (192)Ir source. This TLD depth dependence was assessed by performing measurements at different depths in a water phantom with an (192)Ir source. The variation in the TLD response with depth in a water phantom was not found to be statistically significant for the distances investigated. The TLDs agreed with Acuros(TM) BV within 1.4 % in the air phantom, 3.2 % in the stainless steel phantom, 3 % in the bone phantom and 5.1 % in the titanium phantom. The TLDs showed a larger discrepancy when compared to TG-43 with a maximum deviation of 9.3 % in the air phantom, -11.1 % in the stainless steel phantom, -14.6 % in the bone phantom and -24.6 % in the titanium phantom. The results have shown that Acuros accounts for the heterogeneities investigated with a maximum deviation of -5.1 %. The uncertainty associated with the TLDs calibrated in the PMMA phantom is ±8.2 % (2SD).
authors.affiliation: Department of Medical Physics, Waikato District Health Board, Pembroke Street, Hamilton, New Zealand, siobhan.manning@waikatodhb.health.nz.
authors.forename: Siobhan
authors.initials: S
authors.lastname: Manning
authors.forename: Thulani
authors.initials: T
authors.lastname: Nyathi
mesh_terms: D000465:Algorithms; D001842:Bone and Bones / Q000000981:diagnostic imaging; D002138:Calibration; D016001:Confidence Intervals; D004307:Dose-Response Relationship, Radiation; D005459:Fluorides / Q000737:chemistry*; D007496:Iridium Radioisotopes; D018020:Lithium Compounds / Q000737:chemistry*; D019047:Phantoms, Imaging; D017785:Photons; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011877:Radionuclide Imaging; D011880:Radiotherapy Planning, Computer-Assisted; D013193:Stainless Steel / Q000737:chemistry; D013819:Thermoluminescent Dosimetry / Q000379:methods*; D014025:Titanium / Q000737:chemistry
chemical_list: D007496:Iridium Radioisotopes; D018020:Lithium Compounds; D013193:Stainless Steel; C027651:lithium fluoride; D019904:Polymethyl Methacrylate; D014025:Titanium; D005459:Fluorides