Measurement of Patient Radiation Doses from Digital radiography (DR) for Chest X-ray Examination using optically stimulated luminescence nanoDot dosimeter.

Abstract

Background: Patient radiation doses resulting from X-ray examinations depend on both the X-ray imaging technology and the exposure parameter settings.Objective: This research aimed to determine the optimum x-ray parameters and to evaluate the entrance surface air kerma (ESAK) for patients undergoing chest x-ray examination using digital radiography (DR) system.Method: The determination of the optimum x-ray parameters, the x-ray images of a chest phantom were taken and the radiation output and image quality in terms of signal to noise ratio (SNR) and contrast to noise ratio (CNR) from different combinations of tube voltage (kVp) and tube current-time products (mAs) were evaluated with and without using radiographic grid. For the evaluatation of the patient’s ESAK, the optical stimulated luminescent (OSL) nanoDotÒ dosimeters were applied to the skin of 86 patients of standard size at the center of x-ray beam during the x-ray examination.Results: The results revealed that the optimum x-ray parameters, of which the high image quality at low dose is obtained, were 73 kVp, 200 mA, 0.032 second exposure time, 180 cm source to image receptor distance (SID) and exposed without using grid. The mean ESAK for the patients was 0.19 ± 0.011 mGy. The air kerma measured using OSL nanoDot  and using ionization chamber type X2 R/F sensor  were 0.10 ± 0.0022 mGy and 0.09 ± 0.0013 mGy respectively.Conclusion: The mean ESAK for the patients was significantly lower than that of the national dose reference level of 0.29 mGy. The air kerma measured using OSL nanoDot was significantly lower than that obtained from the ionization chamber type X2 R/F sensor (p ‹ 0.05). The patient’s ESAK should be assessed regularly by the radiological technologist in order to ensure that the patient's radiation dose is acceptable and the image quality is sufficient for  physician's diagnosis.