Beschreibung:
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<jats:italic>Background</jats:italic>
Considerable experimental evidence exists that neointimal hyperplasia after angioplasty is inhibited by γ-irradiation of the treated arteries. A β-particle radiation is absorbed in tissue within a shorter distance away from the source than γ-radiation and may be more suitable for localized vessel irradiation. This study outlines a method to implant a β-particle–emitting radioisotope (
<jats:sup>32</jats:sup>
P; half-life, 14.3 days) into metallic stents. The effects of these stents on the inhibition of neointimal hyperplasia was compared with conventional stents in a rabbit model.
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<jats:italic>Methods and Results</jats:italic>
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P was produced by irradiation of red amorphous phophorus (
<jats:sup>31</jats:sup>
P) with neutrons and was implanted into Palmaz-Schatz stents (7.5 mm in length) after being kept apart from
<jats:sup>31</jats:sup>
P in a mass separator. The radioisotope was tightly fixed to the stents, and the ion implantation process did not alter the surface texture. Stent activity levels of 4 and 13 μCi were chosen for the study. Four and 12 weeks after placement of conventional stents and
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P-implanted stents in rabbit iliac arteries, vascular injury and neointima formation were studied by histomorphometry. Immunostaining for smooth muscle cell (SMC) α-actin was performed to determine SMC cellularity in the neointima. SMCs were quantified by computer-assisted counting of α-actin immunoreactive cells. Endothelialization of the stents was evaluated by immunostaining for endothelial cell von Willebrand factor. No difference in vessel wall injury was found after placement of conventional and
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P-implanted stents. Neointima formation was potently inhibited by
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P-implanted stents only at an activity level of 13 μCi after 4 and 12 weeks. Neointimal SMC cellularity was reduced in
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P-implanted stents compared with conventional stents. Radioactive stents were endothelialized after 4 weeks, but endothelialization was less dense than in conventional stents.
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<jats:italic>Conclusions</jats:italic>
Neointima formation in rabbits is markedly suppressed by a β-particle–emitting stent incorporating the radioisotope
<jats:sup>32</jats:sup>
P. In this model, a dose-response relation with this type of radioactive stent was observed, indicating that a threshold radiation dose must be delivered to inhibit neointima formation after stent placement over the long term.
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