title: A new online detector for estimation of peripheral neutron equivalent dose in organ.
abstract: OBJECTIVE
  Peripheral dose in radiotherapy treatments represents a potential source of secondary neoplasic processes. As in the last few years, there has been a fast-growing concern on neutron collateral effects, this work focuses on this component. A previous established methodology to estimate peripheral neutron equivalent doses relied on passive (TLD, CR39) neutron detectors exposed in-phantom, in parallel to an active [static random access memory (SRAMnd)] thermal neutron detector exposed ex-phantom. A newly miniaturized, quick, and reliable active thermal neutron detector (TNRD, Thermal Neutron Rate Detector) was validated for both procedures. This first miniaturized active system eliminates the long postprocessing, required for passive detectors, giving thermal neutron fluences in real time.
  
  
  METHODS
  To validate TNRD for the established methodology, intrinsic characteristics, characterization of 4 facilities [to correlate monitor value (MU) with risk], and a cohort of 200 real patients (for second cancer risk estimates) were evaluated and compared with the well-established SRAMnd device. Finally, TNRD was compared to TLD pairs for 3 generic radiotherapy treatments through 16 strategic points inside an anthropomorphic phantom.
  
  
  RESULTS
  The performed tests indicate similar linear dependence with dose for both detectors, TNRD and SRAMnd, while a slightly better reproducibility has been obtained for TNRD (1.7% vs 2.2%). Risk estimates when delivering 1000 MU are in good agreement between both detectors (mean deviation of TNRD measurements with respect to the ones of SRAMnd is 0.07 cases per 1000, with differences always smaller than 0.08 cases per 1000). As far as the in-phantom measurements are concerned, a mean deviation smaller than 1.7% was obtained.
  
  
  CONCLUSIONS
  The results obtained indicate that direct evaluation of equivalent dose estimation in organs, both in phantom and patients, is perfectly feasible with this new detector. This will open the door to an easy implementation of specific peripheral neutron dose models for any type of treatment and facility.
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Sevilla 41009, Spain and Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla 41007, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Irazola
authors.affiliation: Departimento di Ingegneria Nuclear, Politecnico di Milano, Milano 20133, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Lorenzoli
authors.affiliation: Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare (INFN), Frascati Roma 00044, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Bedogni
authors.affiliation: Departimento di Ingegneria Nuclear, Politecnico di Milano, Milano 20133, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Pola
authors.affiliation: Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla 41007, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Terrón
authors.affiliation: Instituto de Física, Pontificia Universidad Católica de Chile, Santiago 4880, Chile.
authors.forename: B
authors.initials: B
authors.lastname: Sanchez-Nieto
authors.affiliation: Departamento de Física, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain.
authors.forename: M R
authors.initials: MR
authors.lastname: Expósito
authors.affiliation: Centro de Investigaciones Energéticas y Medioambientales y Tecnológicas (CIEMAT), Madrid 28040, Spain.
authors.forename: J I
authors.initials: JI
authors.lastname: Lagares
authors.affiliation: Centro de Investigaciones Energéticas y Medioambientales y Tecnológicas (CIEMAT), Madrid 28040, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Sansaloni
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Sevilla 41009, Spain and Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla 41007, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Sanchez-Doblado
mesh_terms: D000886:Anthropometry; D002138:Calibration; D015331:Cohort Studies; D004867:Equipment Design; D006801:Humans; D015233:Models, Statistical; D009369:Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000532:radiotherapy; D009502:Neutrons; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011859:Radiography; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D012044:Regression Analysis; D015203:Reproducibility of Results; D018570:Risk Assessment