title: A track length estimator method for dose calculations in low-energy X-ray irradiations: implementation, properties and performance.
abstract: The track length estimator (TLE) method, an "on-the-fly" fluence tally in Monte Carlo (MC) simulations, recently implemented in GATE 6.2, is known as a powerful tool to accelerate dose calculations in the domain of low-energy X-ray irradiations using the kerma approximation. Overall efficiency gains of the TLE with respect to analogous MC were reported in the literature for regions of interest in various applications (photon beam radiation therapy, X-ray imaging). The behaviour of the TLE method in terms of statistical properties, dose deposition patterns, and computational efficiency compared to analogous MC simulations was investigated. The statistical properties of the dose deposition were first assessed. Derivations of the variance reduction factor of TLE versus analogous MC were carried out, starting from the expression of the dose estimate variance in the TLE and analogous MC schemes. Two test cases were chosen to benchmark the TLE performance in comparison with analogous MC: (i) a small animal irradiation under stereotactic synchrotron radiation therapy conditions and (ii) the irradiation of a human pelvis during a cone beam computed tomography acquisition. Dose distribution patterns and efficiency gain maps were analysed. The efficiency gain exhibits strong variations within a given irradiation case, depending on the geometrical (voxel size, ballistics) and physical (material and beam properties) parameters on the voxel scale. Typical values lie between 10 and 10(3), with lower levels in dense regions (bone) outside the irradiated channels (scattered dose only), and higher levels in soft tissues directly exposed to the beams.
authors: Université de Lyon, CREATIS; CNRS UMR5220; Inserm U1044; INSA-Lyon; Université Lyon 1; Centre Léon Bérard, France.
authors: F
authors: F
authors: Baldacci
authors: Department of Physics, LMU Munich, Germany; Faculty of Medicine, LMU Munich, Germany.
authors: A
authors: A
authors: Mittone
authors: European Synchrotron Radiation Facility, Grenoble, France.
authors: A
authors: A
authors: Bravin
authors: Department of Physics, LMU Munich, Germany; Faculty of Medicine, LMU Munich, Germany.
authors: P
authors: P
authors: Coan
authors: Université de Lyon, CREATIS; CNRS UMR5220; Inserm U1044; INSA-Lyon; Université Lyon 1; Centre Léon Bérard, France.
authors: F
authors: F
authors: Delaire
authors: European Synchrotron Radiation Facility, Grenoble, France.
authors: C
authors: C
authors: Ferrero
authors: Department of Physics, LMU Munich, Germany.
authors: S
authors: S
authors: Gasilov
authors: Université de Lyon, CREATIS; CNRS UMR5220; Inserm U1044; INSA-Lyon; Université Lyon 1; Centre Léon Bérard, France.
authors: J M
authors: JM
authors: Létang
authors: Université de Lyon, CREATIS; CNRS UMR5220; Inserm U1044; INSA-Lyon; Université Lyon 1; Centre Léon Bérard, France.
authors: D
authors: D
authors: Sarrut
authors: Université de Lyon, CREATIS; CNRS UMR5220; Inserm U1044; INSA-Lyon; Université Lyon 1; Centre Léon Bérard, France.
authors: F
authors: F
authors: Smekens
authors: Université de Lyon, CREATIS; CNRS UMR5220; Inserm U1044; INSA-Lyon; Université Lyon 1; Centre Léon Bérard, France. Electronic address: nicolas.freud@insa-lyon.fr.
authors: N
authors: N
authors: Freud
mesh_terms: D000465:Algorithms; D000818:Animals; D001822:Body Burden; D003198:Computer Simulation; D006801:Humans; D018499:Linear Energy Transfer; D015233:Models, Statistical; D009010:Monte Carlo Method; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012984:Software; D014965:X-Rays
keywords: Dose calculation; Dosisberechnung; GATE; Kerma approximation; Kerma-Annährung; Monte Carlo simulation; Monte-Carlo-Simulationen; Track length estimator; Track-Length-Estimator; Variance reduction; Varianzreduktion