Monte Carlo simulation of the influence of adjacent TL dosemeters on TL readings in simultaneous measurements in BNCT beams

Boron neutron capture therapy (BNCT) is a binary radiotherapy developed for the treatment of malignant tumours. The main dosemeters for characterising and controlling BNCT beams are activation foils and paired ionisation chambers. Thermoluminescence (TL) dosemeters are also of interest because of their practicality in routine measurements with large numbers of detectors in phantoms. However, in simultaneous measurements TL dosemeters may influence each others' TL readings. In this work Monte Carlo simulation was used to study the shielding effect. In the simulations an epithermal BNCT beam was directed towards a water phantom containing TL detectors, the minimum distance between two detectors being 4 mm. Fluence rate in each detector volume was simulated with and without neighbouring detectors. No significant fluence differences occurred in the cases of thermal and epithermal neutrons or gamma rays. It is concluded that several TL dosemeters can be used in simultaneous measurements without a need for correction factors arising from the shielding by other TL dosemeters present.