Detection of orbital foreign bodies by CT: Are plain radiographs useful?

Purpose: To prove the visualisation of orbital foreign bodies by CT. Materials and methods: In vitro we examined defined small objects of various materials (metal, wood, glass, stone) which are common as orbital foreign bodies. Density and minimum detectable size were studied. The findings of 27 patients with suspected orbital foreign bodies were compared with the results of plain radiographs, Comberg radiographs, sonography, and surgery. Results: For iron, the minimum detectable size was 0.02 mm(3). A differentiation of various materials by CT was not always possible, especially in small objects. There were wide differences in density of wood (-600 HU to +130 HU) according to hardness and water content. The CT scans correctly showed number and location of foreign bodies. Other methods were inferior in detection of foreign bodies. Conclusion: In diagnosis of foreign body injuries of the orbit, CT is the imaging method of choice.