Radiology of foreign bodies: how do we image them?

To assess the sensitivity of detecting the most commonly encountered foreign bodies in Emergency Radiology using all imaging modalities (conventional radiography, computed tomography, ultrasound, and magnetic resonance imaging). The following materials were inserted into a pig-leg phantom and imaged using conventional radiography, computed tomography, ultrasound, and magnetic resonance imaging: Plastics #1, 2, 3, 5, and compostable plastic; dry and wet wood, aluminum, gravel, glass (tinted and non-tinted), and Salmon and Halibut fish bones. The visibility of plastic is variable on both conventional radiography and computed tomography, depending on composition, but all types of plastic are well visualized on ultrasound. Wood is most easily identified and localized on both computed tomography and ultrasound, is only faintly visible on conventional radiography, and is not well visualized on magnetic resonance imaging. Gravel, glass, and aluminum are well visualized on all modalities, with the exception of magnetic resonance imaging, where there is significant artifact surrounding the foreign body. Fish bones (Halibut and Salmon) are well visualized on conventional radiography, computed tomography, and ultrasound. Conventional radiography and computed tomography are great modalities for detecting foreign bodies of various compositions. Computed tomography is particularly useful at localizing the foreign body and determining its relationship to surrounding structures and its depth of involvement. All foreign bodies are visualized on ultrasound if the location is known and the foreign body is in the plane of the transducer. Magnetic resonance imaging is not helpful in detecting foreign bodies.