IMAGING CHARACTERISTICS OF INTRAOCULAR FOREIGN BODIES A Comparative Study of Plain Film X-Ray, Computed Tomography, Ultrasound, and Magnetic Resonance Imaging

Purpose: To determine the imaging features of common intraocular foreign bodies (IOFBs) and the ability to differentiate types of IOFBs. Methods: Four-mm IOFBs were inserted via through pars plana approach into cadaveric lamb eyes. Six metallic (aluminum, brass, copper, silver, steel, and lead) and seven nonmetallic (plastic [CF6 spectacle plastic and polyvinyl chloride pipe], glass [bottle glass and windshield glass], wood [dry and wet poplar], and stone [slate]) IOFBs were imaged using plain film x-ray, computed tomography scan, ultrasound, and magnetic resonance imaging (T1, T2, and gradient echo sequences). Results: Plain film x-ray had limited ability to differentiate most IOFBs. Computed tomography findings can be divided into low attenuation objects (wood), moderate attenuation (CF6 spectacle plastic), high attenuation without surrounding artifact (polyvinyl chloride, slate, bottle glass, windshield glass, and aluminum), high attenuation with shadow artifact and minimal edge streak artifact (steel, brass, copper), and high attenuation with significant shadow artifact and prominent streak artifact (silver and lead). Density (in Hounsfield units) aided in differentiating the types of IOFBs. Gradient echo sequences on magnetic resonance imaging also held utility. Ultrasound images had considerable overlap in appearances. Conclusion: Imaging techniques can significantly aid in determining the IOFBs type, with computed tomography serving as the best initial modality. X-ray holds limited utility while ultrasound and magnetic resonance imaging are best reserved as adjunctive tests.