Fig. 3

Foreign-body detection with x-ray dark-field radiography of a human hand. x-ray dark-field imaging allows for the simultaneous acquisition of a conventional attenuation image (a) and a dark-field image (b) of a human hand fixed in formalin. The images (antero-posterior projection) show the metacarpal and phalangeal bones of the right hand. Two wooden particles and one metallic particle were inserted into the hand to mimic foreign bodies, as shown in the inlay on the upper right. The metallic foreign body is lodged in the soft tissue of the palmar hand in front of the diaphysis of the IV metacarpal bone while the two wooden foreign bodies are located in front of the V metacarpal bones and the intermetacarpal space IV/V, respectively. High atomic number materials like the metallic saw blade provide a strong signal in the attenuation channel as indicated by the black arrows in the magnified attenuation image. However, the x-ray attenuation contrast of dry wood is poor and therefore the wooden test objects are difficult to detect in the attenuation image. In contrast, the dark-field signal is sensitive to small angle scattering at structures at a micron range occurring in wood. Both wooden objects can clearly be detected in the dark-field image which are marked with white arrows in the magnified view of the dark-field image