Repeat analysis program in radiology departments in Mazandaran province- Iran Impact on population radiation dose

Background: The rejected films in radiography may be responsible for an unnecessary increase in the radiation dose to the population. The effective dose to population is a very important factor in estimation of stochastic risk in radiology. The main goal of this study was to determine the effective dose to members of the public due to rejected films in diagnostic radiology departments in the Northern province Mazandaran- of Iran. Materials and Methods: A repeat analysis program was set in all radiology departments in Mazandaran province (population = 2976219 person) to determine the total number and type of rejected films. All repeat and discarded films were collected and separated into types according to the etiology leading to their being discarded. Considering technical data about various radiological procedures and using the standard dosimetry tables, the annual effective dose per caput as well as annual gonadal dose per caput due to image retake was estimated. Results: The total number of rejected radiographs in one year period was 73857 (overall reject rate ~ 11.15%) which led to 34.91 µSv and 37.17 µGy as annual average effective dose to a member of the public and annual average gonadal dose per caput respectively. The main reason of retaking the images was improper exposure factors. Conclusion: The reject rate was in the middle range of similar values in other studies whereas in the present study the main reason for rejection was improper exposure factors (67.11%), the main reason for radiography repeat film was different in various countries. Comparing to the estimated 2.4 mSv from natural background radiation , the average annual effective dose and annual average gonadal dose per caput due to repeat/retake films are negligible. However, reducing the reject films is economically rewarding. Further national studies are suggested.