Use of TLD in evaluating diagnostic reference levels for some radiological examinations

The European Council Directive 97/43 introduces diagnostic reference levels (DRL) for all medical examinations involving ionising radiation. Each department has to evaluate patient dose and to compare that value with the DRL adopted by its member state. Italian law, applying the Directive, states that reference levels must be measured every 2 years. Quantities that must be measured are entrance surface dose or air kerma, or other dosimetric quantities. In our work, clinical measurements on patients were made by positioning a thermoluminescence dosemeter (TLD) over the skin of a statistically significant number of patients for each projection of each examination. As there is no national guideline for these measurements in Italy, the aim of this work was to establish a method based both on European publications and on clinical experience. Three different modalities were considered: conventional radiography, computed radiography and mammography. Accordingly, differently shaped types of TLD were required, especially for mammography where the beam energy is lower.