| 摘要 |
<p>An X-ray responsive filament, which comprises a non-extensible X-ray transparent core material covered with an extruded layer of thermoplastic resin containing an X-ray opaque material, is secured to and extends across one face of a gauze web, which web is folded to give a surgical dressing having a plurality of plies. The filament core material may be natural, artificial or synthetic material (or mixtures thereof), for example cotton, rayon, nylon or polyacrylonitrile, in filamentary form. The thermoplastic resin comprises a polymer or copolymer base material in which fine particles of a radiopaque substance are uniformly dispersed. Suitable base materials include polystyrene, polyolefins such as polyethylene and polypropylene, polyamides such as polycaprolactan (nylon 6), vinyl polymers such as polyvinyl chloride and polyvinylidene chloride, acrylic polymers such as polyethylacrylate, and cellulose derivatives such as cellulose acetate and ethyl cellulose; polyvinyl chloride is preferred. The radiopaque substance preferably is inorganic, for example barium sulphate, thorium dioxide or bismuth trioxide. The filament, which may be made by drawing filamentary core material through orifices in an extrusion head containing molten thermoplastic material, preferably is secured to the web by the application of heat and pressure, for example by passing the unfolded gauze web and filament between complementary opposed heat shoes or rolls. The filament may be radiologically responsive in the form either of a single-line image or of a parallel double-line image; the latter image is given by reason of the tubular shape of the X-ray opaque layer and may be intensified by reason of the flattening of the filament which results from its attachment to the gauze web by hot pressing.</p> |
