Towards the establishment of national diagnostic reference levels for abdomen, KUB, and lumbar spine x-ray examinations in Sri Lanka: a multi-centric study.

Diagnostic reference levels (DRLs) and achievable doses (ADs) provide guidance to optimise radiation doses for patients undergoing medical imaging procedures. This multi-centre study aimed to compare institutional DRLs (IDRLs) across hospitals, propose ADs and multi-centric DRLs (MCDRLs) for four common x-ray examinations in Sri Lanka, and assess the potential for dose reduction. A prospective cross-sectional study of 894 adult patients referred for abdomen anteroposterior (AP), kidney-ureter-bladder (KUB) AP, lumbar spine AP, and lumbar spine lateral (LAT) x-ray examinations was conducted. Patient demographic information (age, sex, weight, BMI) and exposure parameters (tube voltage, tube current-exposure time product) were collected. Patient dose indicators were measured in terms of kerma-area product (P_KA) using a P_KAmeter. IDRLs, ADs, and MCDRLs were calculated following the International Commission on Radiological Protection guidelines, with ADs and MCDRLs defined as the 50th and 75th percentiles of the median P_KAdistributions, respectively. IDRL ranges varied considerably across hospitals: 1.42-2.42 Gy cm²for abdomen AP, 1.51-2.86 Gy cm²for KUB AP, 0.83-1.65 Gy cm²for lumbar spine AP, and 1.76-4.10 Gy cm²for lumbar spine LAT. The proposed ADs were 1.82 Gy cm²(abdomen AP), 2.03 Gy cm²(KUB AP), 1.27 Gy cm²(lumbar spine AP), and 2.21 Gy cm²(lumbar spine LAT). MCDRLs were 2.24 Gy cm²(abdomen AP), 2.40 Gy cm²(KUB AP), 1.43 Gy cm²(lumbar spine AP), and 2.38 Gy cm²(lumbar spine LAT). Substantial intra- and inter-hospital variations in P_KAwere observed for all four examinations. Although ADs and MCDRLs in Sri Lanka were comparable to those in the existing literature, the identified intra- and inter-hospital variations underscore the need for dose reduction without compromising diagnostic information. Hospitals with high IDRLs are recommended to review and optimise their practices. These MCDRLs serve as preliminary national DRLs, guiding dose optimisation efforts by medical professionals and policymakers.