title: Ir-192 HDR transit dose and radial dose function determination using alanine/EPR dosimetry.
abstract: Source positioning close to the tumour in high dose rate (HDR) brachytherapy is not instantaneous. An increment of dose will be delivered during the movement of the source in the trajectory to its static position. This increment is the transit dose, often not taken into account in brachytherapeutic treatment planning. The transit dose depends on the prescribed dose, number of treatment fractions, velocity and activity of the source. Combining all these factors, the transit dose can be 5% higher than the prescribed absorbed dose value (Sang-Hyun and Muller-Runkel, 1994 Phys. Med. Biol. 39 1181-8, Nath et al 1995 Med. Phys. 22 209-34). However, it cannot exceed this percentage (Nath et al 1995). In this work, we use the alanine-EPR (electron paramagnetic resonance) dosimetric system using analysis of the first derivative of the signal. The transit dose was evaluated for an HDR system and is consistent with that already presented for TLD dosimeters (Bastin et al 1993 Int. J. Radiat. Oncol. Biol. Phys. 26 695-702). Also using the same dosimetric system, the radial dose function, used to evaluate the geometric dose degradation around the source, was determined and its behaviour agrees better with those obtained by Monte Carlo simulations (Nath et al 1995, Williamson and Nath 1991 Med. Phys. 18 434-48, Ballester et al 1997 Med. Phys. 24 1221-8, Ballester et al 2001 Phys. Med. Biol. 46 N79-90) than with TLD measurements (Nath et al 1990 Med. Phys. 17 1032-40).
authors.affiliation: Departamento de Física e Matemática, FFCLRP, Universidade de São Paulo, Av Bandeirantes 3900, 14040-901, Ribeirão Preto, SP, Brazil.
authors.forename: Carmen S Guzmán
authors.initials: CS
authors.lastname: Calcina
authors.forename: Adelaide
authors.initials: A
authors.lastname: de Almeida
authors.forename: José R Oliveira
authors.initials: JR
authors.lastname: Rocha
authors.forename: Felipe Chen
authors.initials: FC
authors.lastname: Abrego
authors.forename: Oswaldo
authors.initials: O
authors.lastname: Baffa
mesh_terms: D000409:Alanine / Q000528:radiation effects*; D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007496:Iridium Radioisotopes / Q000032:analysis* / Q000627:therapeutic use*; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D019275:Radiopharmaceuticals / Q000032:analysis / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods
chemical_list: D007496:Iridium Radioisotopes; D019275:Radiopharmaceuticals; D000409:Alanine