Estimation of patient organ doses from CT examinations in Tanzania.

Although the use of computed tomography (CT) in medical diagnosis delivers relatively higher radiation doses to patients than other radiological procedures, lack of optimized protocols could be an additional source of increased dose in developing countries. The aim of this study was to determine the magnitude of radiation doses received by selected radiosensitive organs of patients from CT examinations. The study was further carried out in order to assess the influence of existing CT scanning protocols on patient organ doses. In order to achieve these objectives, patient organ doses from five common CT examinations were obtained from eight hospitals in Tanzania. The patient organ doses were estimated using measurements of CTDI, exposure-related parameters and the NRPB conversion factors. Large variation of mean organ doses among hospitals was observed for similar CT examinations. These variations were largely originated from different CT scanning protocols employed in different hospitals and scanner type. The mean organ doses in this study for the lens of the eyes (for head), thyroid (for chest), breast (for chest), stomach (for abdomen), and ovary (for pelvis), were 63.9 mGy, 12.3 mGy, 26.1 mGy, 35.6 mGy, and 24.0 mGy, respectively. These values were mostly comparable and slightly higher than the values of organ doses reported from literature for the UK, Japan, Germany, Norway and the Netherlands. It was concluded that patient organ doses could substantially minimized through careful selection of scanning parameters based on clinical indications of study, patient size, and body region being examined. Additional dose reduction to superficial organs would require the use of shielding materials.