Evaluation of diagnostic reference levels for conventional radiography in Austria

Purpose: Evaluation of Austrian National Diagnostic Reference Levels (NDRLs). *** Methods and Materials: A nationwide survey on common conventional radiography examinations was conducted. In line with Austrian radiation protection standards, all relevant Austrian hospitals and radiology practices were asked to report a minimum sample of 10 representative dose-area products (DAP) together with patient weight. Participants were invited via email, followed up by reminders to increase participation rates. 59% of invited institutions (67% hospitals, 51% radiology practices) submitted DAP data (n=15305), 31% submitted additional data on patient weight. Case numbers presented varied from 1005 to 2121. Plausibility checks were performed to increase data quality. Third quartiles (Q75) of median DAP of participating institutions were calculated and compared to NDRLs.*** Results: DAP values and interquartile ranges (IQR) are given in cGy*cm2. Third quartiles (Q75) were considerably lower than existing NDRLs. Highest discrepancies (≥50%) were observed for skull AP/PA (Q75: 49, IQR:21, NDRL:100), skull LAT (Q75:49, IQR:21, NDRL:100), chest PA (Q75:13, IQR:6, NDRL:28) and LAT (Q75:42, IQR:21, NDRL:100). Discrepancies of ≥20% occurred for abdomen AP/PA (Q75:184, IQR:92, NDRL:300), pelvis AP (Q75:194, IQR:96, NDRL:300) and lumbar spine LAT (Q75:310, IQR:149, NDRL:400). For lumbar spine AP (Q75:176, IQR:90, NDRL:200) discrepancy was 12%. Q75 for bedside chest X-ray (Q75:20, IQR:10) was significantly (p≤0.01) higher than thorax PA. Average patient weight was 74kg. *** Conclusion: Q75 derived from the survey are on average 40% lower than Austrian NDRLs suggesting an update of NDRLs. Since Q75 correspond nicely to German and Swiss NDRLs, an update would be in accordance with European DRL harmonisation efforts.