The alanine detector in BNCT dosimetry: Dose response in thermal and epithermal neutron fields

• Published in: Medical physics (Lancaster) 2015-01, Vol.42 (1), p.400-411
• Main Authors: Schmitz, T., Bassler, N., Blaickner, M., Ziegner, M., Hsiao, M. C., Liu, Y. H., Koivunoro, H., Auterinen, I., Serén, T., Kotiluoto, P., Palmans, H., Sharpe, P., Langguth, P., Hampel, G.
• Format: Article
• Language: English
• Subjects: 07 ISOTOPES AND RADIATION SOURCES; ABSORBED RADIATION DOSES; Acids; alanine; Alanine - radiation effects; ALANINES; biomedical equipment; Boron; Boron Neutron Capture Therapy - instrumentation; Boron Neutron Capture Therapy - methods; Cobalt Radioisotopes - therapeutic use; Computer Simulation; DEPTH DOSE DISTRIBUTIONS; Dose-Response Relationship, Radiation; dosimetry; Dosimetry/exposure assessment; ELECTRON SPIN RESONANCE; Electron Spin Resonance Spectroscopy; EPITHERMAL NEUTRONS; Gamma Rays - therapeutic use; Graphite; mixed fields; Models, Theoretical; Monte Carlo Method; Monte Carlo methods; Monte Carlo modeling; NEUTRON BEAMS; NEUTRON CAPTURE THERAPY; Neutron radiation effects; neutron sources; neutrons; Neutrons - therapeutic use; organic compounds; paramagnetic resonance; Particle beam detectors; Photons; Probability theory, stochastic processes, and statistics; Production or acceleration of neutral particle beams, e.g. molecular or atomic beams; Protons; Radiation therapy; Radiometry - instrumentation; Radiometry - methods; Scintigraphy; Therapeutic applications, including brachytherapy; THERMAL NEUTRONS; TRIGA-2-MAINZ REACTOR
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.4901299

Purpose: The response of alanine solid state dosimeters to ionizing radiation strongly depends on particle type and energy. Due to nuclear interactions, neutron fields usually also consist of secondary particles such as photons and protons of diverse energies. Various experiments have been carried out in three different neutron beams to explore the alanine dose response behavior and to validate model predictions. Additionally, application in medical neutron fields for boron neutron capture therapy is discussed. Methods: Alanine detectors have been irradiated in the thermal neutron field of the research reactor TRIGA Mainz, Germany, in five experimental conditions, generating different secondary particle spectra. Further irradiations have been made in the epithermal neutron beams at the research reactors FiR 1 in Helsinki, Finland, and Tsing Hua open pool reactor in HsinChu, Taiwan ROC. Readout has been performed with electron spin resonance spectrometry with reference to an absorbed dose standard in a 60Co gamma ray beam. Absorbed doses and dose components have been calculated using the Monte Carlo codes fluka and mcnp. The relative effectiveness (RE), linking absorbed dose and detector response, has been calculated using the Hansen & Olsen alanine response model. Results: The measured dose response of the alanine detector in the different experiments has been evaluated and compared to model predictions. Therefore, a relative effectiveness has been calculated for each dose component, accounting for its dependence on particle type and energy. Agreement within 5% between model and measurement has been achieved for most irradiated detectors. Significant differences have been observed in response behavior between thermal and epithermal neutron fields, especially regarding dose composition and depth dose curves. The calculated dose components could be verified with the experimental results in the different primary and secondary particle fields. Conclusions: The alanine detector can be used without difficulty in neutron fields. The response has been understood with the model used which includes the relative effectiveness. Results and the corresponding discussion lead to the conclusion that application in neutron fields for medical purpose is limited by its sensitivity but that it is a useful tool as supplement to other detectors and verification of neutron source descriptions.