Computed tomography scanner census and adult head dose in Nigeria

Abstract

Background: Inspite of potential detriment from computed tomography (CT) procedures, there is increasing installation and use of the medical imaging modality in Nigeria. Computed tomography dose monitoring and reporting have however, not received commensurate attention. Objective: To carry out a census of CT scanners in Nigeria and, to assess a representative sample for dose. Methodology: A physical count of the scanners was done using radiographers spread across the country. Twenty of those scanners were then assessed for head dose using volume computed tomography dose index (CTDIvol), and dose-length product (DLP) extracted retrospectively and manually from the operating console. The mean, as well as the 75th percentile, were then calculated for all subjects with the aid of statistical packages for the social sciences (SPSS), version 20.0. Results: A total of 183 CT scanners were installed in Nigeria as at March 2018. A huge number of these (57.4%, n = 105) belonged to private investors while the federal and state governments jointly owned 78 scanners (42.6%). The Christian-dominated South had far more scanners installed (n = 116) than the Muslim-dominated North and FCT (n = 67). Three states in northern Nigeria had no single scanner installed. A sizeable number (83%, n = 151) of the scanners were functional as at March 2018. The CT dose was assessed using scanners from General Electric (GE), Toshiba, Philips, Siemens and Neusoft. CereTom was the only model left out due to low distribution and inaccessibility. The slice capacity ranged from 4 to 128. Tube potential was uniform (120 kVp) in the centres while tube current was within a narrow range (200–250 mA). The dose for head investigation amongst the adult population had a mean/75th percentile of 57/63 mGy (CTDIvol) and 1336/1431 mGy·cm (DLP), respectively. This is fairly comparable to a similar work from Kenya but higher than the recommendations of the European Commission. Conclusion: Computed tomography scanners distinctly located in Nigeria were 183. The first installation in the country was in 1987, suggestive of an annual average of 6 installations. Dose from different facilities showed wide variations. The establishment of national diagnostic reference levels (nDRLs) to reduce arbitrariness in dose administration is imperative. While this is awaited, radiographers have a moral and ethical obligation to pay more attention to optimization of patient protection. Keywords: CT scanners, Dose, CTDI, DLP, Optimization, CT census