Induced nuclear reactions: processes – systems – and elements – Nuclear transmutation – By neutron bombardment
Reexamination Certificate
1999-02-19
2001-02-20
Jordan, Charles T. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Nuclear transmutation
By neutron bombardment
C376S314000, C600S003000
Reexamination Certificate
active
06192095
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to angioplasty as a means of treating arterioscleorosis of coronary arteries. More particularly, the invention relates to a radioactive stent capable of preventing restenosis of blood vessels and a process for producing it.
Stated more specifically, the present invention relates to a radioactive cylindrical stent that has been ion injected with
133
Xe and which will later emit &bgr;-rays, &ggr;-rays and internal conversion electrons ejected by &ggr;-decay. The invention also relates to a process for producing the stent. The radioactive stent of the invention is placed within a blood vessel and prevents its restenosis by inhibiting abnormal growth of the smooth muscular cells in it. The advantage of the
133
Xe radioactive stent of the invention is not limited to preventing blockage recurrence after angioplasy with a balloon or an ordinary non-radioactive stent; it can also replace the balloons and ordinary non-radioactive stents commonly used in angioplasy.
To treat arteriosclerosis of coronary arteries, angioplasy is performed using balloons and stents; however, postoperative stenoses often occur and the frequency is 30 -40% in the case of using balloons and 10-30% with stents. Opened blood vessels are believed to occlude mainly from abnormal growth of smooth muscular cells and it has recently been found that intravascular exposure to radiations is an effective way to prevent postoperative restenoses (Waksman R. et al., Circulation, 91, (1995) 1533-1539).
One of the ways to implement the intravascular exposure to radiations is by using a stent that has been rendered radioactive on its own and this technique is gaining increasing attention from researchers. However, the only case that has been reported on radioactive stents that are prepared by ion injection is about a &bgr;-emitting radioactive stent that has been ion injected with
32
p (Hehrlein C. et al., Circulation, 93, (1996) 641-645).
A problem with this prior art technique is that due to the comparatively long half-life (14.3 days) of
32
p, the time of exposure to the emitted &bgr;-rays is unduly prolonged to interfere with the regeneration of vascular endothelia, potentially inducing thrombus formation. Therefore, it is necessary to develop a stent that has been rendered radioactive by means of a shorter-lived radioisotope and which is capable of preventing restenosis of blood vessels without interfering with the regeneration of vascular endothelia.
In addition, in view of the fact that restenosis of a blood vessel occurs in that area of the vessel which is in contact with any surface of the inserted stent, it is required that the entire surface of the stent be uniformly ion injected with a radioactive isotope. Considering the number of patients with arteriosclerosis who are currently under treatment, mass production of radioactive stents is also an important factor.
SUMMARY OF THE INVENTION
According to the present invention, a radioactive stent is produced by injecting
33
Xe as a nuclide that has a shorter half-life and emits a smaller maximum energy of &bgr;-rays than
32
p In the invention, a uniform irradiator is employed to enable uniform ion injection into the surface of a stent. Since
133
Xe is a nuclear fission product, an ion injector may be connected to a nuclear reactor to achieve continuous ion injection of
133
Xe, thereby enabling mass production of radioactive stents.
Thus according to its first aspect, the present invention provides a
133
Xe radioactive stent for preventing restenosis of blood vessels that is prepared by ion injecting
133
Xe into the entire surface of a cylindrical stent and which retards the growth of the smooth muscles of blood vessels by means of &bgr;-rays and internal conversion electrons emitted from the injected
133
Xe.
According to its second aspect, the present invention provides a process for producing
133
Xe radioactive stent for preventing restenosis of blood vessels which comprises performing ion injection of
133
Xe on a stent positioned in a uniform irradiating unit within an ion injector, whereby
133
Xe is uniformly injected into the entire surface of the stent.
According to its third aspect, the present invention provides a process for mass production of
133
Xe radioactive stents for preventing restenosis of blood vessels, in which
133
Xe that is a nuclear fission product generated upon irradiating
235
U in fuel rods in a nuclear reactor with neutrons is supplied into an ion injector via a piping so that it is continuously ion injected into the surfaces of stents.
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patent: 5485835 (1996-01-01), Vande Streek et al.
patent: 5607442 (1997-03-01), Fischell et al.
patent: 5863284 (1999-01-01), Klein
patent: 5906573 (1999-05-01), Aretz
patent: 5919126 (1999-07-01), Armini
patent: 19819426 (1999-11-01), None
Mallinckrodt Medical, Inc., “Radioactive Gas Solution and Method of Prevention of Restenosis,” Research Disclosure, p. 593, May 1998.
Gillette et al., “Review of Radioisotopes Program, 1964,” Oak Ridge National Laboratory, ORNL-3802, pp. 25-26, 52, May 1965.
Wilson et al., “Preparation of Xenon-133 Radiography Sources from Spent Fuel,” Nucleonics, pp. 110-114, Apr. 1958.
Ikonen et al, “Selective Assessment of Single-Lung Graft Function with Xe-133 Radiospirometry in Acute Rejection and Infection,” Chest, V109, N4 (Apr. 1996), pp. 879-884, (abstract only).
Wagner, H.N., Jr., “Medical Applications of low-energy X-ray and gamma radiation sources,” ORNL Proc. of Sump. on Low-Energy X-ray Sources and Gamma Sources and Appl., pp. 239-242, (abstract only), Nov. 1965.
Kawano et al., “Remnants of 133Xe Radioactivity in a Gas Container,” Journal of Health Physics, vol. 21, vo. 4, pp. 262-264, (abstract only), 1986.
Nagayama, K., “Evaluation of New Methods for Measuring the Hepatic Blood Circulation in Chronic Liver Diseases,” Tokyo Jikeikai Ika Daigaku Zasshi, 111(4), pp. 423-440, 1996.
D'Angelo et al., “Operation Modes of SiCPICal Detector for SPECT Applications,” Nucl. Sci. J., 32(5), pp. 413-421, 1995.
Carter, et al., Effects of Endovascular Radiation From a &bgr;-Particle-Emitting Stent in a Porcine Coronary Restenosis Model,Circulation1996; 2364-68.
Aoyagi Keiko
Hasegawa Akira
Hoshino Yoichi
Ishioka Noriko
Koizumi Mitsuo
Banner & Witcoff , Ltd.
Japan Atomic Energy Research Institute
Jordan Charles T.
Mun K. Kevin
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