PubMed · 9424643
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A Aletto, P Giardini, A L Bianchin, P Sardo. [Vitreous replacement and computerized tomography].. https://pubmed.ncbi.nlm.nih.gov/9424643/
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OBJECTIVE: This study aimed to evaluate the ability of spiral computed tomography (CT) and multiplanar reconstruction in the assessment of intraocular foreign bodies. DESIGN: The study design was experimental. MATERIAL: Three foreign bodies (metal, glass, and plastic) implanted into the globe of a cadaveric head were studied. INTERVENTION: Spiral CT in the axial plane was used. Beam collimation and table increment were both 3 mm, whereby overlapping axial slices were reconstructed at 1-mm intervals. The data were transferred to a workstation, and reconstructions in the coronal and sagittal plane were performed. MAIN OUTCOME MEASURES: The ability to detect and evaluate localization, shape, and size of the foreign bodies in all three imaging planes was assessed. RESULTS: All foreign bodies were detected in the axial and in both reconstructed planes. The metal foreign body caused imaging artifacts in the axial plane. In the reconstructed planes. imaging artifacts were less severe, and evaluation of localization and shape was improved. Glass and plastic foreign bodies were well seen in all planes, and shape and localization were well demonstrated. Appropriate window settings improved determination of size of the different foreign bodies. CONCLUSIONS: Spiral CT of the orbit and multiplanar reconstruction offers a promising tool for evaluation of intraocular foreign bodies. Advantages of spiral CT compared to conventional CT are data acquisition in only one axial plane; shortened examination time; reduced radiation exposure; reduced imaging artifacts from metallic foreign bodies in the reconstructed planes; and demonstration of localization, shape, and size of the foreign body in three imaging planes.
BACKGROUND: Perfluorocarbon liquids (PFCLs) are useful for floating various materials off the posterior retina during vitreoretinal surgery. It is generally assumed that buoyancy forces restrict this use to objects with specific gravity lower than that of PFCLs. METHODS: We tested potential intraocular foreign body materials with specific gravities ranging from 1.1-8.7. The relative affinities of each material for saline and PFCL (specific gravity 1.94) were determined. For each material, we then tested the ability of several specimens of increasing surface/volume ratio to float at the saline-PFCL interface in a glass beaker. RESULTS: All materials with specific gravity higher than PFCL demonstrated a greater affinity for saline than for PFCL. Specimens of each of these dense materials floated at the saline-PFCL interface, provided that the surface/volume ratio of the specimen was above a critical value. The critical surface/volume ratio for each material was directly proportional to its specific gravity. CONCLUSIONS: PFCLs may be useful for manipulating a variety of intraocular foreign bodies, even those with specific gravities higher than PFCL. Surface forces, in addition to buoyancy, govern the disposition of small foreign bodies at the saline-PFCL interface.