Detection of rib fractures in an abused infant using digital radiography: a laboratory study

To assess the diagnostic performance of digital radiography using charge-coupled device (CCD) technology in the detection of rib fracture in infant abuse.

Four fractured posterior rib arcs and eight normal ribs removed at autopsy from a 10-month-old abused infant were radiographed using a CCD prototype, four clinical film-screen systems, and direct-exposure film. Each rib was viewed with these six systems in nine different projections. The resultant 648 images were assessed for probability of fracture (0-100%) by four pediatric radiologists. The calculated area under the resultant ROC curves (A(z)) for the CCD was compared with those obtained with direct-exposure, high-detail, medium and fast film-screen radiographic systems.

The mean A(z) for the CCD (0.937) fell within the range of the high-detail systems (0.934-0.940) and was significantly higher (p < 0.05) than the medium and fast system (0.861 and 0.858, respectively). Despite a lower spatial resolution than direct-exposure film (7 line pairs per millimeter vs. > 20 line pairs per millimeter) the CCD performance was comparable (A(z) = 0.944 vs. 0.937). The similar performance can be explained by the higher contrast resolution of the digital technology.

This study indicates that in the ex vivo setting, digital radiology can perform comparably to high-detail film-screen imaging. The findings suggest that digital radiography has the potential to replace film-screen imaging in the evaluation of inflicted skeletal injury in infants.