The overarching objective of the project is to determine values of RBE for neutrons, for specific tissues and neutron energies, which can then be validated using paediatric proton therapy data.  Each task in the project forms an essential component part of this objective.  The individual task objectives can be split up as follows:

(i)  Physical characterisation, using measurements and modelling, of the neutron fields of various energy spectra used for experimental irradiation of cells, and generated during paediatric radiotherapy for the purpose of accurate dosimetry and track structure simulation and model development of the damage response;

(ii)  Investigation of the damage induction in stem cells as an indicator of the relative carcinogenic effectiveness of low and intermediate doses from neutrons compared to photons; use of the results to generate provisional values for RBE and explore the dependence on neutron energy and dose;

(iii)  Integration of functional relationships from biophysical simulations and radiobiological stem cell experiments to develop predictive neutron risk models for second primary malignancies following paediatric proton therapy that can be validated using clinical treatment and follow-up data: proof-of-principle pilot study leading to design of a multi-centre prospective study.