Survey of Chest X-Ray Examination in Iran and Suggestion of National Diagnostic Reference Level

Diagnostic radiography examinations of patients comprise the largest contribution to various medical uses of ionizing radiation. Investigation of dose reduction methods in diagnostic radiology has always been a primary aim of radiation protection research. Chest radiography examination is the most frequently performed radiological procedure. Although the patient dose from chest radiography is relatively low, but since a large population is involved it makes a significant contribution to the collective effective dose from all medical x-ray examinations. A total of 20 randomly selected x-ray units located in 16 public hospitals in 14 cities throughout Iran and 306 patients were included in this survey. The following five quality control tests have been performed using an UNFORS Mult-O-Meter, model 303: 1- kVp accuracy 2- Timer accuracy 3- mAs linearity 4- Exposure reproducibility 5- Filtration check. The Entrance Surface Dose (ESD) received by the patients was measured using thermoluminescence dosimeters (TLD-100) attached to the patient's skin. Complete details of quality control tests results, characteristics of patients, exposure parameters and patient dose values are presented in 9 figures and 3 tables. The results have shown wide variation of mean hospital doses. The difference between the maximum and minimum individual patient dose values varied up to a factor of 52.Discussion and Although the reasons for dose variations were complex, but in general, low tube potential, high mAs and low filtration were associated with high dose rooms. The 75 percentile value of the ESD distribution was 0.44 mGy and it is suggested to be used as "National Diagnostic Reference Level" of chest examination in PA projection in Iran. This study also demonstrated the need for performing routine quality control tests on x-ray units.