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C.Y. Shih, A. Schrier, L. Kleiman, W. Au; CT versus X–Ray in the Evaluation of Intracorneal Metallic Foreign Bodies . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1339.
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To compare the efficacy of X–ray versus Computed Tomography (CT) in the evaluation of intracorneal metallic foreign bodies.
Shavings of five types of metal – lead, copper, iron, aluminum, and bronze, were reduced to the following lengths: 0.5 mm, 1.0 mm, and 1.5 mm using a surgical blade. These pieces were then placed under lamellar flaps created in fifteen different bovine eyes. After visual confirmation of the placement of the metallic foreign bodies, an orbital X–ray (70 kV and 16 mA) was taken and an axial CT scan was done using 2 mm slices and an orbital protocol (120 kV and 35 mA). All scans were read by a radiologist at Columbia Presbyterian Medical Center.
By CT, 73% of all eyes were read as positive and 27% as negative. All eyes containing copper, lead, and bronze, regardless of size were read as positive. The eye with the 0.5mm piece of iron was read as negative as compared to the eyes which contained 1.0mm and 1.5mm pieces of iron, which were read as positive. All eyeballs containing aluminum were read as negative by CT–scan. By X–ray, 53% of all eyes were read as positive, 27% as equivocal, and 20% as negative. All eyes containing bronze and lead were read as positive. However, due to the presence of artifact, the eyes containing copper and iron were read as "equivocal" 67% of the time. (p value = 0.04, student t–test).
CT scan is more sensitive than X–ray in assessing for the intracorneal metallic foreign bodies evaluated in this study – especially those made of iron, lead, copper, and bronze. However neither CT nor X–ray is effective in detecting aluminum foreign bodies embedded in the cornea.
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