Organ Dose Distribution and Estimated Cancer Risk to Paediatric Patients Undergoing Computed Tomography in a Nigerian Tertiary Hospital

Aims: The aim of this research work is to estimate the organ dose distribution and the associated radiation induced cancer risk for some commonly performed Computerized Tomography (CT) examinations in a tertiary medical facility in South Nigeria.

Study Design: The study was designed to estimate the radiological implications of radiation dose that the paediatric patients were exposed to during routine CT examinations.

Place and Duration of Study: Department of Radiology, Obafemi Awolowo University Teaching Hospital Complex, (OAUTHC), Ile-Ife, Nigeria, between August 16, 2011 to August 15 2012.

Methodology: Well calibrated thermoluminescent dosimeters (LiF-100) were attached to the skin of paediatric patients such as skull, chest, abdomen, and pelvic in the path of the primary X-ray beam to determine radiation exposure during CT examination. The effective dose was calculated from the equivalent dose obtained from OAUTHC, and the cancer risk associated was estimated by multiply age-dependent lifetime cancer mortality risk (per unit dose) with estimated age-dependent doses produced by various CT examinations.

Results: Out of 258 paediatric patients scanned the equivalent dose measured for abdominal CT scan ranged from 23.49 - 55. 26 mSv; skull CT scan ranged from 10.07 – 69.94 mSv and chest CT scan ranged from 8.60 – 31.94 mSv. The peak tube voltage (kVp) used range from 80 – 140 while the exposure current-time product (mA) range from 30 – 300. The abdominal CT scan had the highest cancer risk ranging from digestive 37.5% to lung cancer risk of 0.4%. The risks estimated in this work were higher than the ICRP recommended value. Reducing the millampere-second setting of the equipment for paediatric without significant loss of radiological information will reduce this risk.

Conclusion: In this study the estimated cancer risk to paediatric patients undergoing CT is high. This is in keeping with findings in a previous study thus emphasizing the need to standardize and optimize radiation dose in paediatric patients undergoing CT in Nigeria so as to keep cancer risk at the minimum.