OPTIMIZATION OF RADIATION DOSE AND IMAGE QUALITY IN CHEST RADIOGRAPHY USING DIGITAL MOBILE X-RAY SYSTEM AT KING CHULALONGKORN MEMORIAL HOSPITAL

Abstract

Digital Radiography (DR) has become an important imaging modality at Department of Radiology, King Chulalongkorn Memorial Hospital. In September 2013, the digital mobile x-ray system has been in service on the patient ward for patients who could not move to the Department of Radiology. Chest radiography is the most common examination performed on the patient ward. Some patient was exposed several times during treatment, result in increasing the radiation dose. As the DR produces less patient radiation dose than the CR and conventional radiograph, the exposure parameters use for DR must be determined. The purpose of this study is to optimize the radiation dose and image quality for digital mobile chest radiography. Lung Phantom was firstly used to study the appropriate exposure parameters to optimize the radiation dose at surface of the phantom and image quality based on the Commission of European Communities (CEC) and the qualitative noise evaluated by three observers. The exposure parameters obtained will be further used for patients. The proper exposure parameter for chest radiography was kVp 90 and mAs 0.63 for the patient chest thickness equal to or less than 23 cm. 50 patients were exposed by optimal parameters, then the patient dose had been calculated and the image quality has been assessed by three observers. The average patient dose was 0.076 mGy and the average of patient chest thickness was 19.70 cm. 88% of the images showed the image criteria score equal to or more than 3 where the acceptable score range from 3 to 6, 70% and 30% of the images showed the qualitative noise scores was 2 and 3 respectively where the acceptable score range from 2 to 3. The patient dose for routine chest study was 0.192 mGy. Therefore, the patient dose using optimal protocol was 60% less than routine study and also lower than the International Atomic Energy Agency dose reference level of 0.4 mGy for chest radiography.