Diagnostic Reference Levels for Head and Abdominal Computed Tomography of Adult Patients in Selected States in South-South Nigeria

Context: Diagnostic reference level (DRL) is the first step in the optimization process to manage patient dose corresponding with the medical purpose. Aim: The objective of this study was to develop local DRL for computed tomography (CT) of the head and abdomen in adult patients in four CT centers in South-South Nigeria. Materials and Methods: A prospective, cross-sectional study of 546 adult patients that underwent CT examination of the head and abdomen from 2018 to 2020 using four different CT scanners. Volume CT dose index (CTDI vol ) and dose length product (DLP) of contrast and non-contrast CT examinations of the head and abdomen were collated and the 50 th percentile DRL was determined and compared to other published DRLs. Results: The 50 th percentile CTDI vol /DLP for non-contrast head CT examination for centers A, B, C, and D was 75.3 mGy/1776.6 mGy.cm, 21.8 mGy/457 mGy.cm, 17.4 mGy/373.6 mGy.cm, and 29.6 mGy/628.5 mGy.cm, respectively. The 50 th percentile CTDI vol /DLP for contrast head CT examination for centers A, B, C, and D was 150.6 mGy/3326.2 mGy.cm, 41.4 mGy/832.4 mGy.cm, 35.6 mGy/653.6 mGy.cm, and 77.9 mGy/1458.4 mGy.cm, respectively. The 50 th percentile CTDI vol /DLP for non-contrast abdomen CT examination for centers A and B was 22.8 mGy/1488.5 mGy.cm and 7.9 mGy/302.3 mGy.cm, respectively. The 50 th percentile CTDI vol /DLP for contrast abdomen CT examination for centers B and C was 19.6 mGy/825.7 mGy.cm and 31.5 mGy/1555.5 mGy.cm, respectively. There was correlation between contrast and non-contrast CTDI ( P = 0.003) and DLP ( P = 0.025) for the head. Conclusion: Wide variations CTDI vol and DLP values were observed among the centers for similar body part CT examinations.