Entrance surface dose from two diagnostic x-ray centers in Nigeria for three common radiological examinations is presented in this study. Entrance surface doses for 294 patients drawn from Niger state hospital Minna and Two-Tees x-ray centre, Ibadan are included in this dose survey. The air kerma for each patient was measured using thermoluminescent dosimeter chips (TLD-100). The air kerma for each patient was then multiplied by a back scatter factor of 1.35 to obtain the Entrance surface dose. Generally doses obtained in this study were found to be higher than those in published works and International Atomic Energy Agency recommended limits for chest examination. The range factor at Niger State General Hospital was as high as 12 in some cases but as low as 1 in most cases at Two-Tees X-ray center. The doses obtained for skull and abdomen examination were found to be within acceptable International Atomic Energy Agency recommended limit.

Patients' dose audit reports in some Nigerian hospitals had shown large inter-and intra-hospital variations for the same radiological examinations. They have thus presented the need, to have a national standard for radiological diagnostic procedures and set dose limits for individual x-ray examination centers in Nigeria. These will go a long way in reducing inter-and intra-hospital dose range factors, thus reducing doses to as low as reasonably achievable and consistent with clinical objectives of the examinations. In establishing a national dose limit for medical radiological examinations, there is a need to have a national dose survey. This paper suggests a reasonable and easy procedure for achieving a national radiological dose survey. Due to its simplicity of measurement, the use of entrance surface dose as the dose parameter to be used for setting the dose limit as recommended by the European Union and the International Atomic Energy Agency (IAEA) is also suggested. ESD can be measured directly through the use of solid state detectors, or indirectly by measuring free air exposure which can later be converted to ESD using standard formula. The methods of measuring the entrance surface dose and how to derive the dose limit from them are also highlighted.