Worldwide about one million patients require treatment of stenosed coronary arteries annually. Often a tubular stainless steel mesh (stent) is implanted to mechanically support the injured vessel. Restenosis, an abundant complication (20%–30%) can be prevented, if the vessel is treated with ionizing radiation. Stents can deliver radiation if they are made radioactive. The radio isotope P32 is well suited when ion implanted. Radioactive ions sources require high efficiency to keep the radioactive inventory small. Reliability, ease of operation, and maintenance are mandatory. A small emittance is important to minimize losses during mass separation and beam transport. A 2.45 GHz ECR source was developed for the implantation of P32. The source consists of two coils for the axial and a permanent hexapole for the radial confinement. The microwaves are fed in radially by a loop connected to a silver plated brass tube surrounding the plasma chamber. The plasma chamber is made from Pyrex. Neutron activated phosphorus, containing 30 ppm P32, is introduced from the rear end on a rod. As support gas D2 is used. By this P+32 can be separated from (31PD)+. The extraction is done in two steps: 60 kV–30 kV–ground. Mass separation is accomplished by a double focusing 90° magnet (radius 500 mm). During four years of operation about 1000 radioactive stents per year have been provided for animal experiments and clinical trials. Only one maintenance to exchange the extraction system due to degradation of high voltage stability was required so far.
Background-Balloon-expandable -particle-emitting ( 32 P) stents inhibit within-stent neointimal hyperplasia but induce lumen narrowing beyond the stent margins, ie, the so-called "edge effects." Methods and Results-We prospectively investigated the performance of novel stents impregnated with the ␥-emitting isotope 103 Pd, designed to reduce edge effects, in 24 rabbits. The stents had a length of 18 mm and were mounted on 20-mm-long delivery balloons for deployment. Angiograms were obtained immediately and 1 month after direct implantation of control and 1-, 2-, and 4-mCi 103 Pd stents into the iliac arteries without predilatation or postdilatation. Late lumen loss was measured with quantitative angiography. Neointimal hyperplasia and vascular remodeling were evaluated by histomorphometry. Late lumen loss was inhibited within 103 Pd stents (control 0.18 mm, 1 mCi 0.08 mm, 2 mCi 0.05 mm, and 4 mCi Ϫ0.03 mm, PϽ0.05 all activities versus control). Conversely, late lumen loss occurred at the edges of 103 Pd stents, correlating with areas of high balloon/artery ratios and vessel overstretch injury. Edge effects were primarily due to neointimal hyperplasia but were also caused by negative vessel remodeling at high stent activities. Conclusions-Edge effects after implantation of radioisotope stents can occur independently of the isotope chosen for stent impregnation.
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