Kebede, Tesfaye(MD, Associate Professor of Radiology)Dr.Teferi, Seife (Ph.D), Associate ProfessorMiliard, Hermon2020-02-102023-11-052020-02-102023-11-052019-11http://etd.aau.edu.et/handle/123456789/20594Background The thyroid gland, located between C5 and T1 vertebrae, is a butterfly shaped endocrine gland which is divided into two lobes and connected by an isthmus [1]. Along with the breast, lung and bone marrow, thyroid gland is among the most sensitive organs for radiation due to their rapid cell division [2]. The potential risk factors for thyroid carcinoma development include genetic predisposition, exposure to therapeutic or environmental ionizing radiation, residence in areas of iodine deficiency or excess, history of preexisting benign thyroid disease, as well as hormonal and reproductive factors. [3] The radiation dose (mGy) towards the thyroid gland is greater during Chest CT as compared to Head CT and Paranasal sinus CT. The association between radiation exposure and the occurrence of thyroid cancer has been well documented, and the two main risk factors for the development of a thyroid cancer are the radiation dose delivered to the thyroid gland and the age at exposure. The risk increases after exposure to a mean dose of more than 0.05-0.1 Gy (50100mGy). The risk is more important during childhood and decreases with increased age at exposure, being low in adults [4]. Objective This study is designed to assess the rate of unnecessary radiation exposure to the thyroid gland in patients who presented to radiology department and had Computed Tomography of the chest at Tikur Anbessa Specialized Hospital. Method Hospital based retrospective cross-sectional study was conducted on 1306 patients who underwent a chest CT at TASH and thyroid gland inclusion in these studies along with the CT dose of the studies were evaluated over a period of 6 months from July 2018 to January 2019. 7 Data was collected by evaluating chest CT scans from PACS (Medweb). The data was checked for clarity and completeness. Computerized data analysis was conducted by using SPSS version 24.0 software. Result 1803 Chest CT scans were done over a period of 6 months out of which, 341 were chest along with another body part (chest + abdomen, chest + head and neck, etc); 83 had missing variables (such as DLP, CTDIvol and/or mean CTDI); 35 had thyroid pathology; 23 scans were done for CT guided biopsy purpose and 15 patients had scans done at least twice within this time frame for which the most latest scan was reported and the others reported as ‘previous CT’s. These data’s, in accordance with the exclusion criteria, were not included. 1306 patient CT scan were included in this study over a period 6 months. Intravenous iodinated contrast media was used in 95.4% of the CT scans. Thyroid was included in 99.8% of the scans, out of which 76.9% included the whole thyroid gland. 12.6% of the patients were scanned previously in addition to the current one. Among the patients who had previous CT scans, 75.3% had one previous scan and 24.7% had two previous scans. Female had lower scan length compared to male. There was a tendency for linear increment in scan length as age increases. The mean ED was slightly higher than the recommended ED of 57mSv with, however, 5% (calculated by conversion factor of ICRP 60) and 7% (ICRP 103) were exposed for higher than the recommended ED (2-20mSv).en-US Thyroid radiation,Chest CT examThesis