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This Defense Intelligence Agency reference document, dated 7 January 2010 and prepared under the Acquisition Threat Support series, surveys biomaterials used in medicine. It covers biocompatibility, biosensor membranes, silicones, Teflon, biodegradable polymers, hydrogels, titanium, bioceramics, tissue constructs, cardiovascular stents, contact lenses, drug delivery and dialysis. It concludes that biomaterial performance underlies many medical devices, that the industry is slow to adopt new materials because of testing costs, and that innovation mainly involves new applications of established materials.
UNCLASSIFIED//F8A GilFFHil ft L Ui:ili 0Nk¥ Heart valves are another application of biomaterials in which the materials are in direct contact with blood. They are typically constructed using a form of stainless steel and woven Teflon (or Dacron) as a suture ring to anchorthe device. Figure 24 shows one of these devices. STENT BIOMATERIALS A stent is a metal mesh tube that looks something like a Chinese finger puzzle and is used to prop open a clogged artery. These a re delivered to the heart in a catheter on the end of a wire usually inserted into an artery in the groin. The stent is collapsed to a small diameter and placed over a balloon Figure 24. Stainless Steel and Tenon Bjork Shiley Heart valve catheter. It is then surgically moved into the area of the blockage. When the balloon is inflated, the stent expands, locks into place, and forms a scaffold that holds the artery open. Figure 25 shows an artist's conception of this process. The stent stays in the artery permanently, holds it open, improves blood flow to the heart muscle, and relieves symptoms (usually chest pain). Within a few weeks after the stent was placed, the inside lining of the artery (the endothelium) grows over the metal surface of the stent. Stents are often made from a form of stainless steel that is ductile enough to be expanded by a balloon and then resist closure forces of the vessel wall a~er the balloon is removed. The insertion and use of the balloon to expand the stent involves some hazards that can be overcome if the stent is made from a self-expanding metal called Nitinol™. With a nitinol Plaque Dilated balloon catheter and stent I Stent deployed Figure 25. Illustration of stent Placement. The stent is used to expand the luminal opening of a clogged blood vessel. stent, the stent is placed into the body collapsed while it is held cold by a flow of refrigerated saline through the catheter. When allowed to heat up to body temperature by shutting off the cold water to the catheter, the stent expands and more reproducibly applies a calibrated amount of pressure to the blood vessel Walls. 18 UNCLASSIFIED//PIHI 9FPIIIILIIL Yl!!H! e,tL'■'
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 32 pages are in the text index: search them above, or from the library's search.