Cellular damage and dose enhancement assessment of natural gadolinium neutron capture from thermal neutron beam irradiation using Monte Carlo methods*

Gadolinium neutron capture therapy (GdNCT) has emerged as a theoretically promising alternative to current gamma and electron radiotherapies. Gd has one of the highest thermal neutron capture cross sections. When irradiated, it releases huge amounts of energy in the form of gamma and low energy, high LET electron cascades. These secondary particles offer a very promising modality of local dose enhancement, ultimately sparing more healthy tissue. Geant4 is used to model a 100nm thick layer of Gd deposited on an aluminum substrate separated from a model human cell by several centimeters and placed in a thermal neutron beam. The single- and double-strand breaks and overall RBE and dose enhancement caused by these secondaries is analyzed using Geant4-DNA and python codes.