A new design policy for protective barriers in departments of x-ray diagnosis

In order to calculate the thicknesses of protective barriers requried in departments of radiodiagnosis for walls, floors, ceilings, protective screens, etc., it is necessary to make an assessment of work load and occupancy factor in each direction. In order to ensure that barriers are safe, it is customary to assume that all the radiological procedures are carried out at the greatest kVp value used in the room in question, and to look up the necessary thicknesses from prepared tables. In fact, only a small fraction of work load is carried out at the highest kilovoltage, and also it is found that a considerable fraction of the total work load is directed downwards. A computer program has been written to use data available from comprehensive analyses of work load broken down into suitable kVp intervals. As the cost of providing the necessary protective barriers can be anything from a few hundred pounds to several thousand pounds, the use of exact values for work load separated into kVp ranges for each direction can lead to substantial savings in cost amounting to hundreds of pounds per room whilst still satisfying the requirements of the Code of Practice for the Protection of Persons against Ionizing Radiations arising from Medical and Dental Use (HMSO, 1972). Departmental surveys were carried out to establish the distribution of work load in kVp and direction, and also to ascertain dosage levels to the staff and within existing rooms. The results show that in practice the doses are such that the reduced barriers found by the method described would be entirely satisfactory.