Patient-Specific Radiation Dose and Cancer Risk in Computed Tomography Examinations in Ondo, Nigeria

Introduction: The dose in computed tomography (CT) often approach or exceed the optimum levels, thereby increasing the probability of cancer induction. With wide application of this diagnostic test, it is expedient to determine the effective dose (ED) for each patient to estimate their cancer risk. This study was conducted to investigate the patient-specific dose (PSD) and cancer risk in CT examinations in Ondo, Nigeria. Material and Methods: The study was conducted on 160 patients undergoing eight most common types of CT examinations performed at the center, from December 5, 2015 to February 28, 2016. Body mass index (BMI) was calculated for each patient using demographic data, PSD was determined and estimation of the lifetime attributable risk (LAR) of cancer was accomplished using the Biologic Effects of Ionizing Radiation VII (2006) report phase 2 models. Results: From the results, radiation doses varied significantly within and between the types of CT examinations. The mean ED was 5.88±3.75 mSv in a range of 0.78-19.00 mSv. The mean PSD was 0.274±0.229 mSv/kgm-2 in a range of 0.024-1.555 mSv/kgm-2 and the mean LAR of cancer incidence was 0.04861±0.03996 Sv-1 in a range of 0.00004-0.21942 Sv-1. Conclusion: ED and PSD varied within and across the CT examinations. In this regard, the coefficients of variation of ED for abdominal, cranial, craniocervical, abdomen/pelvis, thoracic, thoracoabdominal, cervical spine, and pelvis were 5.7%, 6.6%, 3.9%, 8.9%,3.7%, 6.0%, 44.7%, and 19.2%, respectively. Accordingly, the coefficients of variation of PSD were 9.0%, 7.9%, 7.0%, 10.1%,5.6%,23.8%, 47.7%, and 14.2%.