title: Peripheral equivalent neutron dose model implementation for radiotherapy patients.
abstract: OBJECTIVE
  Neutron peripheral contamination in high-energy radiotherapy implies an increase of secondary radiation-induced cancer risk. Although peripheral neutron dose (PND) has been evaluated in organs, few studies have been performed regarding patient size. This work aims to improve an existing methodology for adult patient PND estimations to generalize it to young and children, for its implementation in treatment planning systems (TPS).
  
  
  METHODS
  As a first step, we aimed to generalize the previous model to be usable with any thermal neutron detector. Then, taking into account total neutron spectra and dose-to-point thermal neutron fluence measurements for three phantom sizes (adult, teen and child) and two common treatment locations (H&N and abdomen), the new model was proposed. It represents an upgraded parameterization and extension of the existing one, including patient anatomy. Finally, comparison between estimations and measurements, as well as validation against the original model, was carried out for 510 measured patients.
  
  
  RESULTS
  Concordance found between experimental and theoretical estimations makes us confident about later implementation in treatment planning systems. Comparison among the previous and upgraded models shows no significant differences for the adult case. However, an important underestimation (34.1% on average) can be observed regarding child case for the original one.
  
  
  CONCLUSIONS
  An improved generalization of an existing PND model, considering patient anatomy has been validated and used in real patients. The final methodology is easily implementable in clinical routine and TPS thanks to the ready availability of input parameters (patient height and weight, high-energy MU and facility characterization).
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain; Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain. Electronic address: leticia@us.es.
authors.forename: L
authors.initials: L
authors.lastname: Irazola
authors.affiliation: Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Terrón
authors.affiliation: Instituto de Física, Pontificia Universidad Católica de Chile, Santiago de Chile, Chile.
authors.forename: B
authors.initials: B
authors.lastname: Sánchez-Nieto
authors.affiliation: Istituto Nazionale di Fisica Nucleare, Frascati, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Roberto
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain; Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Sánchez-Doblado
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003198:Computer Simulation; D006801:Humans; D008962:Models, Theoretical; D009010:Monte Carlo Method; D009381:Neoplasms, Radiation-Induced / Q000517:prevention & control; D009502:Neutrons / Q000627:therapeutic use*; D017785:Photons / Q000627:therapeutic use; D011878:Radiotherapy / Q000295:instrumentation; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*
keywords: Peripheral neutron dose model