Patient Dosimetry and Staff Protection at the Clatterbridge High Energy Neutron Facility

Abstract

Abstract The Clatterbridge High Energy Neutron Facility was designed to provide a neutron beam comparable to an X ray beam generated by a modern linear accelerator in terms of both dose distribution and patient positioning. This has been achieved using a cyclotron which accelerates protons to 62 MeV, and an isocentric treatment unit incorporating a variable collimator. Neutrons are generated by the interaction of the proton beam with a beryllium target situated in the treatment head. The neutron beam is described in terms of the beam parameters measured for routine clinical use. Where relevant, they are compared with those of an 8 MV X ray beam. The neutron and X ray beams are also compared by means of treatment plans produced for the two beams. Finally, the dose equivalent to radiographic staff caused by the neutron activation of the treatment machine and room are presented and discussed. These are found to be comparable with that measured at other facilities employing neutron beams with similar energies.