title: Experimental measurement and Monte Carlo assessment of Argon-41 production in a PET cyclotron facility.
abstract: In a medical cyclotron facility, (41)Ar (t1/2 = 109.34 m) is produced by the activation of air due to the neutron flux during irradiation, according to the (40)Ar(n,γ)(41)Ar reaction; this is particularly relevant in widely diffused high beam current cyclotrons for the production of PET radionuclides. While theoretical estimations of the (41)Ar production have been published, no data are available on direct experimental measurements for a biomedical cyclotron. In this work, we describe a sampling methodology and report the results of an extensive measurement campaign. Furthermore, the experimental results are compared with Monte Carlo simulations performed with the FLUKA code. To measure (41)Ar activity, air samples were taken inside the cyclotron bunker in sealed Marinelli beakers, during the routine production of (18)F with a 16.5 MeV GE-PETtrace cyclotron; this sampling thus reproduces a situation of absence of air changes. Samples analysis was performed in a gamma-ray spectrometry system equipped with HPGe detector. Monte Carlo assessment of the (41)Ar saturation yield was performed directly using the standard FLUKA score RESNUCLE, and off-line by the convolution of neutron fluence with cross section data. The average (41)Ar saturation yield per one liter of air of (41)Ar, measured in gamma-ray spectrometry, resulted to be 3.0 ± 0.6 Bq/µA*dm(3) while simulations gave a result of 6.9 ± 0.3 Bq/µA*dm(3) in the direct assessment and 6.92 ± 0.22 Bq/µA*dm(3) by the convolution neutron fluence-to-cross section.
authors.affiliation: Department of Industrial Engineering, Laboratory of Montecuccolino, University of Bologna, Via dei Colli 16, 40136, Bologna, Italy. Electronic address: angelo.infantino@unibo.it.
authors.forename: Angelo
authors.initials: A
authors.lastname: Infantino
authors.affiliation: Department of Industrial Engineering, Laboratory of Montecuccolino, University of Bologna, Via dei Colli 16, 40136, Bologna, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Valtieri
authors.affiliation: Medical Physics Department, University Hospital "S. Orsola-Malpighi", Via Massarenti 9, 40138, Bologna, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Cicoria
authors.affiliation: Medical Physics Department, University Hospital "S. Orsola-Malpighi", Via Massarenti 9, 40138, Bologna, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Pancaldi
authors.affiliation: Department of Industrial Engineering, Laboratory of Montecuccolino, University of Bologna, Via dei Colli 16, 40136, Bologna, Italy.
authors.forename: Domiziano
authors.initials: D
authors.lastname: Mostacci
authors.affiliation: Medical Physics Department, University Hospital "S. Orsola-Malpighi", Via Massarenti 9, 40138, Bologna, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Marengo
mesh_terms: D001128:Argon; D017357:Cyclotrons; D009010:Monte Carlo Method; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D011868:Radioisotopes
chemical_list: D011868:Radioisotopes; D001128:Argon
keywords: Argon-41; FLUKA; Gamma-ray spectrometry; Medical cyclotrons; Monte Carlo; Radiation protection