Broad-beam transmission data in lead for scattered radiation produced at diagnostic energies

Abstract

The growth of interventional techniques in radiology and the consequent close proximity of staff to patients during screening emphasizes the need for provision of proper protective clothing and for appropriate personnel monitoring for radiological staff. In order to comply fully with the Ionising Radiation Regulations (HMSO, 1985a) and the associated Approved Code of Practice and Guidance Notes (HMSO, 1985b; HMSO, 1988), an employer must demonstrate not only that staff doses are below any relevant limits but also that they are as low as is reasonably practicable. Since heavy protective aprons may be unduly inconvenient to wear and since routine personnel monitoring makes use of just one or two dosemeters, it is important for both the optimization of protective clothing and the estimation of whole body effective dose equivalent (IPSM, 1977) that the broad beam shielding properties of lead under relevant working conditions are known (Faulkner & Harrison, 1988). Although there are several sources which tabulate the broad beam shielding characteristics of lead and other materials at diagnostic X-ray energies (BSI, 1971; HMSO, 1971; O'Riordan & Brotherton, 1968; Binks, 1943; NCRP, 1976), a number of limitations exist when these data are applied in practice to lead apron shielding: (1) the data represent primary beam attenuation whereas personnel need to be protected against scatter; (2) data for only a limited number of tube voltages are represented possibly leading to difficult interpolation; (3) a very large range of thicknesses is covered by the data and accuracy may be compromised at the low lead equivalent thicknesses of aprons.