• ambient equivalent dose
• linac
• neutron dosimetry
• radiobiology
• radioprotection
• radiotherapy
• rem counter

Most of linear accelerators used in radiotherapy (linacs) produce high energy ( ≥ 10 MeV) electrons and photons, which induces photoneutron creation through (γ , n) reactions. As energy increases, the photoneutron contribution to the total dose becomes less and less negligible. These photoneutrons originated mainly in the head of the linac, in the surrounding structures and in the air.
The aim of this work was to compare and realign the responses of different rem counters used in the north-west area of Tuscany by exposing them to neutrons produced by radiation of different qualities, including neutrons from Am-Be sources (typically also used for the calibration of such instruments) and photoneutrons produced by linacs operating in the hospitals of Lucca, Livorno and Massa Carrara. The operating dosimetric quantity used for the inter-comparison was the ambient equivalent dose H*(10).
Graphs showing the deviation of different instruments from a reference one (provided by INFN Pisa and recently calibrated) were obtained for all radiation qualities. The gamma-ray emission induced by neutron activation was also measured inside several treatment rooms.
The availability of a calibrated rem counter made it possible to realign the answers of the other instruments and therefore have the possibility of correcting and unambiguously comparing the measurements carried out at different centers.
The LUPIN (Long-interval, Ultra-wide dynamic, PIle-up free, Neutron REM counter), made available by the Politecnico of Milan and particularly suitable for measurements in high intensity pulsed fields, was also compared to other rem counters in some measurement sessions.