title: Spline modelling electron insert factors using routine measurements.
abstract: There are many methods available to predict electron output factors; however, many centres still measure the factors for each irregular electron field. Creating an electron output factor prediction model that approaches measurement accuracy--but uses already available data and is simple to implement--would be advantageous in the clinical setting. This work presents an empirical spline model for output factor prediction that requires only the measured factors for arbitrary insert shapes. Equivalent ellipses of the insert shapes are determined and then parameterised by width and ratio of perimeter to area. This takes into account changes in lateral scatter, bremsstrahlung produced in the insert material, and scatter from the edge of the insert. Agreement between prediction and measurement for the 12 MeV validation data had an uncertainty of 0.4% (1SD). The maximum recorded deviation between measurement and prediction over the range of energies was 1.0%. The validation methodology showed that one may expect an approximate uncertainty of 0.5% (1SD) when as little as eight data points are used. The level of accuracy combined with the ease with which this model can be generated demonstrates its suitability for clinical use. Implementation of this method is freely available for download at https://github.com/SimonBiggs/electronfactors.
authors.affiliation: Riverina Cancer Care Centre, Wagga Wagga, New South Wales 2650, Australia. Electronic address: mail@simonbiggs.net.
authors.forename: S
authors.initials: S
authors.lastname: Biggs
authors.affiliation: Riverina Cancer Care Centre, Wagga Wagga, New South Wales 2650, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Sobolewski
authors.affiliation: Radiation Oncology Queensland, Rockville, Queensland 4350, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Murry
authors.affiliation: Epworth Radiation Oncology, Epworth HealthCare, Richmond, Victoria 3121, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Kenny
mesh_terms: D000465:Algorithms; D004583:Electrons; D006801:Humans; D008962:Models, Theoretical; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy*; D016011:Normal Distribution; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D035501:Uncertainty
keywords: Bivariate spline modelling; Data interpolation; Electron output factor; Electron therapy; Insert factor