د.محمد عامر الجماعي2026-06-292026-06-29https://dspace.academy.edu.ly/handle/123456789/2419Although computed tomography (CT) represents only a small percentage of radiological examinations, it is nonetheless a major source of the collective dose to the population from medical x-ray procedures [1]. This undesirable feature is bound to remain unchanged since CT scanners still deliver high dose per examination and the number of CT examinations in the population is on the increase [2]. As a result, the use of this modality has been of great concern due to undesired health effects to the population such as induction of cancer [3]. In view of these concerns, a number of studies globally have been investigating possible methods to minimise radiation dose to patients from CT examinations without compromising the image quality required for diagnostic accuracyCT is a diagnostic imaging modality giving higher patient dose in comparison with other radiological procedures. The aims of this study are, first, to determine the magnitude of radiation doses received by selected organs of patients undergoing CT examinations, secondly to assess how CT scanning protocols in practice affect patient organ doses. In order to achieve these objectives, patient organ doses from four common CT examinations were obtained from sixteen hospitals in Libya with different CT models. The Impact survey data were used to determine the parameters related to patient dose. This was done by correlating the measurements from the National Radiological Protection Board (NRPB-R250) scanners with the effective dose calculated, using the CT-EXPO software. Patient dose index in air (CTDIair) was measured a function of tube exposure ranged from 80 to 250 mAs at constant kVp and slice thickness, using a special pencil-shaped ionisation chamber and phantoms as well as TLD chips for surface dose measurements . RESULTS: The mean organ doses in this study for head, chest, abdomen and for pelvis were 61.5 mGy, 28.5 mGy, 38.4 mGy, and 24.0 mGy, respectively. These values were slightly higher than the values of organ doses reported from the literature.study for establishment national reference dose levels from ct scanning