The fixed horizontal neutron therapy beam at Edinburgh: dosimetry and radiation protection

A compact cyclotron producing 15 MeV deuterons has been installed at the Western General Hospital, Edinburgh, to extend the Medical Research Council's clinical trials of fast neutrons. Two treatment rooms are available one of which has an isocentric unit and the other a fixed horizontal beam which is the subject of this paper. A radiation protection survey has demonstrated safe levels of radiation throughout the building although there is some activation of the fixed horizontal beam cone resulting in doses to radiographers of 10 mrem per week. The calibration of neutron dose is discussed and the measurements of dose distribution described. Isodose and depth-dose data for both the neutron and photon components of the field are presented.