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Neutron Model Upgrade for Radiotherapy Patients Monitoring Using a New Online Detector

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L Irazola

L Irazola1,2*,M Lorenzoli3*,J.A. Terron 2*, R. Bedogni 4*, A. Pola 3*,B. Sanchez Nieto 5*,M. Romero-Exposito 6*, F. Sanchez Doblado 1,2* (1)Departamento de Fisiologia Medica y Biofisica, Universidad de Sevilla, Spain (2)Servicio de Radiofisica, Hospital Universitario Virgen Macarena, Sevilla, Spain (3)Politecnico di Milano, Departimento di Ingegneria Nuclear, Milano, Italy (4)Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare (INFN), Italy (5)Instituto de Fisica, Pontificia Universidad Catolica de Chile, Santiago, Chile (6)Departamento de Fisica, Universitat Autonoma de Barcelona, Spain


SU-E-T-249 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

The purpose of this work is to improve the existing methodology to estimate neutron equivalent dose in organs during radiotherapy treatments, based on a Static Random Access Memory neutron detector (SRAMnd) [1]. This is possible thanks to the introduction of a new digital detector with improved characteristics, which is able to measure online the neutron fluence rate in the presence of an intense photon background [2]. Its reduced size, allows the direct estimation of doses in specific points inside an anthropomorphic phantom (NORMA) without using passive detectors as TLD or CR-39. This versatility will allow not only to improve the existing models (generic abdomen and H&N [1]) but to generate more specific ones for any technique.

The new Thermal Neutron Rate Detector (TNRD), based on a diode device sensitized to thermal neutrons, have been inserted in 16 points of the phantom. These points are distributed to infer doses to specific organs. Simultaneous measurements of these devices and a reference one, located in front of the gantry, have been performed for the mentioned generic treatments, in order to improve the existing model.

These new devices have shown more precise since they agree better with Monte Carlo simulations. The comparison of the thermal neutron fluence, measured with TNRD, and the existing models, converted from events to fluence, shows an average improvement of (3.90±3.37) % for H&N and (12.61±9.43) % for abdomen, normalized to the maximum value.

This work indicates the potential of these new devices for more precise neutron equivalent dose estimation in organs, as a consequence of radiotherapy treatments. The simplicity of the process makes possible to establish more specific models that will provide a better dose estimation.

[1] Phys Med Biol 2012; 57:6167-6191.
[2] A new active thermal neutron detector. Radiat. Prot. Dosim. (in press).

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