title: Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the University of Mainz.
abstract: To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the University of Mainz, Germany, it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma field. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron flux measurements using gold foil activation and pin-diodes. Material and methods. When L-α-alanine is irradiated with ionizing radiation, it forms a stable radical which can be detected by electron spin resonance (ESR) spectroscopy. The value of the ESR signal correlates to the amount of absorbed dose. The dose for each pellet is calculated using FLUKA, a multipurpose Monte Carlo transport code. The pin-diode is augmented by a lithium fluoride foil. This foil converts the neutrons into alpha and tritium particles which are products of the (7)Li(n,α)(3)H-reaction. These particles are detected by the diode and their amount correlates to the neutron fluence directly. Results and discussion. Gold foil activation and the pin-diode are reliable fluence measurement systems for the TRIGA reactor, Mainz. Alanine dosimetry of the photon field and charged particle field from secondary reactions can in principle be carried out in combination with MC-calculations for mixed radiation fields and the Hansen & Olsen alanine detector response model. With the acquired data about the background dose and charged particle spectrum, and with the acquired information of the neutron flux, we are capable of calculating the dose to the tissue. Conclusion. Monte Carlo simulation of the mixed neutron and gamma field of the TRIGA Mainz is possible in order to characterize the neutron behavior in the thermal column. Currently we also speculate on sensitizing alanine to thermal neutrons by adding boron compounds.
authors.affiliation: Institute for Nuclear Chemistry, University of Mainz, D-55099 Mainz, Germany. sctoschm@students.uni-mainz.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Schmitz
authors.forename: Matthias
authors.initials: M
authors.lastname: Blaickner
authors.forename: Christian
authors.initials: C
authors.lastname: Schütz
authors.forename: Norbert
authors.initials: N
authors.lastname: Wiehl
authors.forename: Jens V
authors.initials: JV
authors.lastname: Kratz
authors.forename: Niels
authors.initials: N
authors.lastname: Bassler
authors.forename: Michael H
authors.initials: MH
authors.lastname: Holzscheiter
authors.forename: Hugo
authors.initials: H
authors.lastname: Palmans
authors.forename: Peter
authors.initials: P
authors.lastname: Sharpe
authors.forename: Gerd
authors.initials: G
authors.lastname: Otto
authors.forename: Gabriele
authors.initials: G
authors.lastname: Hampel
mesh_terms: D016754:Boron Neutron Capture Therapy / Q000295:instrumentation / Q000379:methods*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000473:pathology / Q000532:radiotherapy; D005720:Gamma Rays / Q000627:therapeutic use*; D005858:Germany; D056945:Hep G2 Cells; D006785:Hospitals, University; D006801:Humans; D008113:Liver Neoplasms / Q000532:radiotherapy / Q000556:secondary; D008954:Models, Biological; D009502:Neutrons / Q000627:therapeutic use*; D009688:Nuclear Reactors / Q000295:instrumentation; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D054928:Validation Studies as Topic