Daryoush Khoramian - MSc Graduate, Department of Medical Physics, Faculty of Medicine, Tarbiat Modares University, Tehran, Iran.
Soroush Sistani - MSc Graduate, Department of Medical Physics, Student Research Community, Semnan University of Medical Sciences, Semnan, Iran

Introduction: Beside advantages of the use of CT scanning in medical imaging, there is an increasing concern due to increasing dose received by the patients. Although CT scan is fast and accurate imaging modality and help physicians diagnose wide range types of disease, but high radiation dose from this modality and increase the risk of secondary cancers have been a worldwide issue. Through this and importance of CT dosimetry, we estimated Lifetime Attributable Risk (LAR) of cancer incidence and mortality from chest CT scanning in women, which perform with and without z-axis Automatic Exposure Control (AEC) system. Materials and methods: Patients’ protocols which effect on dose were gathered during a month and LAR of cancer incidence and mortality for each patient were estimated on two situations (with and without AEC). Organ equivalent dose to the breast were estimated with CT-expo dose calculation software according to ICRP report no. 103 tissue weighting factors. Also risk estimation was based on the Biological Effects of Ionizing Radiation V (BEIR V) risk estimation model report. Breast equivalent doses with and without the use of AEC were ranged between 4.5-13.7 and 5.1-15.7 mSv respectively. Results: Differences between breast dose in an individual patient in two situations, with and without AEC, were significant (p<0.05). Maximum LAR of cancer incidence and mortality values without AEC for 35 years old women were 21.67 and 5.28 per 100,000 respectively. Minimum LAR of cancer incidence and mortality values with AEC for 64 years old women were 0.9675 and 0.6774 per 100,000 respectively. Conclusion: Our results indicated that AEC system has potential to reduce LAR of cancer incidence and mortality in chest CT scanning.

Lifetime attributable risk of cancer, Chest CT, Automatic exposure control