Imaging and profiling of absorbed dose in neutron capture therapy

Imaging and profiling of the absorbed dose in tissue-equivalent gel phantom s exposed to thermal neutrons were performed at the TAPIRO fast reactor (EN EA, Italy). The proposed method, aimed at supporting the planning of neutro n capture therapy, allows measurement of three-dimensional distributions of the therapy dose not only in tumors but also in normal tissue. This featur e is very important, because the value of the maximum fluence admitted for therapy is limited by the dose absorbed in the healthy tissue. Fricke-infus ed gel phantoms were designed that allow imaging of the absorbed dose by me ans of optical analysis, based on the detection of visible-light absorbance with a charge-coupled device camera. Moreover, the various components of t he secondary radiation contributing to the dose can be separated through th e differential analysis of images obtained with gels with different element al compositions. Dose mapping in a phantom was also performed with thermolu minescent dosimeters (TLDs). A method for separating the different dose con tributions was studied. based on the analysis of the glow-curve shapes of d ifferent kinds of TLDs. The agreement of the results obtained with the two techniques confirmed the validity of the methods. Fluence measurements perf ormed with activation techniques and Monte Carlo simulations gave further s upport.