Fast neutron therapy at Edinburgh: staff protection

The major hazards encountered by staff using neutrons for radiotherapy are discussed. Specific reference is made to the experience gained at the MRC Cyclotron Unit at the Western General Hospital, Edinburgh, using neutrons generated by the d(15 MeV) + Be reaction. The neutron therapy facility consists of a cyclotron and both a fixed horizontal and an isocentric therapy beam, and staff protection during five years' operation is reviewed. Levels of induced activity in the cyclotron and therapy equipment are reported and problems of radioactive contamination discussed. Summaries of whole-body and finger dose equivalents received by engineering staff, and of whole-body dose equivalents received by physics and radiography staff, are presented and analysed. It is shown that, although doses received by staff are higher than for staff in an X-ray facility, they are all well below the maximum permissible levels, and it is also concluded that radioactive contamination of staff is minimal.