Radiation doses in computed tomography: Need for optimization and application of dose reference levels in Nigeria

Abstract

Background: Establishment and use of diagnostic reference levels (DRLs) is essential for proper use and audit of ionizing radiation in medicine and other radiation applications. Nigeria does not yet have a guideline for DRL. The European Commission reference dose levels were applied to routine computed tomography (CT) examinations in Nigeria's major hospitals. Aim: To determine the dose of CT examinations at the University College Hospital, Ibadan, Nigeria and provide a template for dose optimization. Materials and Methods: Data were obtained from a GE Brightspeed multidetector CT scanner. The dose characteristics and estimates were derived from computed tomography dose index (CTDI vol ), and dose length product (DLP) with the effective dose (E) calculated using software developed by ImPACTscan group with the National Radiological Protection Board-S250 conversion coefficients data for a random sampling of 1 per 10 typical CT patients. Results: The mean values of CTDI vol in mGy were 73.5 ± 4.2 (head), 22.7 ± 6.7 (chest), 37.9 ± 5.6 (abdomen), 28.2 ± 8.3 (abdomen-pelvis), 41.4 ± 13.2 (cervical spine), and 40.1 ± 4.2 (lumbar spine) examinations. The corresponding mean values of DLP in mGy.cm were 1898, 1189, 1902, 2548, 1372, and 1563, respectively. The calculated E values in mSv for the above examinations were 2.8, 11.8, 22.5, 39.6, 4.6, and 29.0, respectively. All values consistently exceeded recommended ECRDLs except the CTDI vol for chest, cervical, and abdomen-pelvis examinations. Conclusion: CT doses were higher than EC recommended guidelines necessitating a need for optimization of CT practice and the requirement for a CT dose survey in Nigeria.