برآورد دز موثر اندام های حساس به پرتو ناشی از آزمایشات قفسه سینه، با و بدون سیستم کنترل اکسپوژر اتوماتیک

Introduction: There are several techniques for reducing the delivered dose from CT scans such as the automatic exposure control (AEC). This technique regulates the tube current regarding the patient size and weight. The aim of this study was estimation the effective and equivalent dose for radiosensitive organs in women undergoing chest CT scans with or without AEC system using the patient’s CT dose index (CTDI) measurements. Material and Methods: Exposure parameters were gathered from 54 women undergoing chest CT scan. 25 of these scans were performed using AEC and 29 of them were performed without AEC. CTDIs in the center and peripheral regions of the standard phantom were calculated using the exposure parameters. Weighted CTDI was also calculated and effective and equivalent organ doses were obtained using CT-Expo dose calculation software for two mentioned groups. In addition noise was measured for these two groups as an image quality parameter. Results: Calculated weighted CTDIs were 9.94 mGy and 12.46 mGy using AEC and without using AEC, respectively. The effective doses were calculated based on the ICRP report number 103, and equaled to 5.4 miliSiverts and 6.3 miliSiverts using AEC and without using AEC, respectively. Maximum organ effective doses were 15, 14, 14 and 14 miliSiverts for breast, esophagus, lung and thymus respectively in the non-using AEC system imaging technique. Discussion and Conclusion: Our measurements indicated a decrease about 15% in dose but an increase about 11.3% in noise using AEC system; however, this increase in noise was in the standard ranges regarding to the standard levels of the Hounsfield unit limits (±5 HU). Therefore, it can be concluded that using of AEC was an effective way for dose reduction in women undergoing chest CT.