Guidance on the use of protective lead aprons in medical radiology protection efficiency and correction factors for personal dosimetry

Workers in clinical radiology wear lead aprons when standing in the vicinity of a patient being exposed to x-rays. A lead apron protects the person's trunk against radiation scattered rom the patient. Our research is focused on two main issues: 1. How much protection does a lead apron provide, and what are the main factors that determine the protection efficiency 2. How can measured badge dose be translated into a realistic estimate of the effective dose, and how does this depend on dosemeter placement Using a model for x-ray shielding and dosimetry we calculated equivalent organ doses and personal depth dose HP(10) for various exposure conditions, x-ray energies and types of aprons that occur in clinical practice. We concluded that apron model and fit are often more important than lead thickness. In others, increasing lead thickness of a badly chosen apron will not provide better protection. For many fluoroscopy applications an apron of good model and fit need not be thicker than 0.5 mm of lead (equivalent). In case of intensive and frequent interventional work lead we advise higher lead thickness (0.35 mm), and preferably additional neck shielding for protection of the oesophagus and thyroid. A well chosen lead apron reduces effective dose by 75%up to 90%. We also concluded that the dosemeter badge should always be worn outside the apron, at mid front of collar or chest. In our view this dosemeter position enables reliable evaluation of effective dose from badge readings. As a standard practice we recommend translating measured badge dose to effective dose by dividing by a factor of five, provide that the worker wears a suitable lead apron. Finally, some research was done on the subject of the protective effect of lead aprons for the uterus, and the relation of uterus dose and badge dose. Use of a lead apron is found to reduce uterus dose by a factor of 5 to 10. Our study shows that in case of worker pregnancy, exposure of the unborn child may de adequately monitored by a specifically designated dosemeter worn locally under the lead apron. (Author)