Original Contribution to the Methodology of Diagnostic Reference Level Setting for Low-Resource African Radiology Departments: Theory, Practice, and Application in Nigeria

Diagnostic reference levels are a fundamental radiation dose optimisation instrument endorsed by the ICRP and IAEA, yet their implementation methodology has been developed for high-income healthcare systems with comprehensive dose data infrastructure, medical physics support, and regulatory enforcement capacity that are largely unavailable in Nigerian and sub-Saharan African radiology departments. This study makes an original methodological contribution to diagnostic reference level setting adapted for low-resource African radiology contexts, with Nigeria as the primary application case. The study develops a theoretically grounded alternative DRL methodology through four components: a systematic review of DRL setting methodologies across low-resource healthcare contexts globally; an original pragmatic dose data collection methodology using simplified survey instruments and low-cost dose measurement proxies validated against reference standard measurements at 15 Nigerian hospitals; a national dose survey applying the pragmatic methodology across 120 Nigerian radiology departments from all six zones, generating the first nationally representative dose data for six common examination categories; and a simulation study comparing DRL values generated by the pragmatic methodology against values derived from standard IAEA methodology, quantifying methodological bias. The original Simplified African DRL Methodology provides a five-step process requiring neither medical physicist on-site support nor digital dose tracking infrastructure. Available DRL methodology literature from sub-Saharan Africa identifies absence of dose data as the primary barrier to national DRL establishment across 30 African countries. The IAEA Technical Report Series No. 457 DRL methodology and Dose Optimisation Theory provide the theoretical reference. Keywords: diagnostic reference levels, methodology, low-resource settings, Nigeria, radiation dose optimisation.