RESUMO
Background: Modern CT might deliver higher image quality than necessary for fracture imaging, which would mean non-essential effective radiation exposure for patients. We simulated ultra-low dose (ULD)-CT at different dose levels and analyzed their diagnostic performance for scaphoid fracture detection. Methods: 30 consecutive high quality CT with clinically suspected scaphoid fractures were assessed. ULD-simulations were made at 20%, 10% and 5% of original dose. Three readers at different levels of experience (expert, moderate, inexperienced) expressed their diagnostic confidence (DC; 5-point-Likert-scale) and analyzed the presence and classification of scaphoid fractures within Krimmer's and Herbert's classifications. Effective radiation exposure of the original data sets and ULD-CT were calculated. Results: At 20% and 10% dose the more experienced readers reached perfect sensitivity (100%) and specificity (100%), showing perfect agreement regarding fracture classification (1.00). Diagnostic performance decreased at 5% dose (92.86% sensitivity, 100% specificity; expert reader). The inexperienced reader showed reduced sensitivity and specificity at all dose levels. At 10% dose minimal DC of all readers was 3/5 and mean calculated effective radiation exposure was 1.11 [±0.36] µSv. Conclusions: The results suggest that ULD-CT at 10% dose compared to high quality CT might offer sufficient image quality to precisely detect and classify scaphoid fractures, if moderate experience of the radiologist is granted.