Surgery – Radioactive substance applied to body for therapy
Reexamination Certificate
1998-11-18
2001-02-20
Lacyk, John P. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Reexamination Certificate
active
06190302
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a method of prevention or treatment of restenosis by irradiation and, more particularly, to a method of treatment of restenosis by external stereotactic irradiation.
The most common therapy for ischemic heart disease is percutaneous transluminal coronary angioplasty, or “balloon” angioplasty, in which a constricted coronary artery is dilated by the insertion of a balloon. One complication of this therapy is that restenosis, or recurrent narrowing, occurs in 30%-40% of dilated arteries. To prevent this, a stent often is implanted in the dilated segment. As a foreign material, the stent induces the proliferation of smooth muscle cells in the vessel walls, so that the restenosis is not eliminated, but is only reduced to about 20%. Therefore, the implantation of the stent may be supplemented with radiotherapy, in which a radioisotope is inserted into the dilated segment or into the implanted stent in order to prevent the proliferation of the smooth muscle cells. This is time consuming, requires costly safety arrangements in the catheterization laboratory, should be performed during invasive catheterization, presents a problem of non-homogeneous irradiation of the dilated segment and adjacent segments (depending on centralization of the radioisotope) as well as different vessel wall layers, and has logistical problems because of the short half life (order of days to months), and consequent short shelf life, of the radioisotopes.
Stereotactic radiotreatment is a recognized therapy for deep seated brain tumors. See, for example, Wendell Lutz, Ken R. Winston and Nasser Maleki, “A system for stereotactic radiosurgery with a linear accelerator”,
Int. J. Radiation Oncology Biol. Phys
. Vol. 14 pp. 373-381 (1988). In this mode of therapy, beams of ionizing radiation, typically gamma radiation from a radioisotope such as
60
Co or from a linear accelerator, are directed at the tumor from several angles. All the beams pass through the tumor, but each beam passes through a different portion of the tissue lo outside the tumor. In this way, a therapeutic dose of radiation is delivered to the tumor without damage to the surrounding tissue.
In order for stereotactic radiotreatment to succeed, the location of the target of the treatment must be known precisely, and the radiation source must be aimed precisely at the target. This is possible in the case of brain tumors, which are fixed in position relative to the patient's head, and whose location can be determined by non-invasive means, but not in the case of moving targets such as coronary arteries. Therefore, it has not been possible heretofore to treat restenosis with stereotactic radiotreatment, despite the advantages that such treatment would have over the present method of radioisotope insertion or implantation.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method of stereotactic radiotreatment or prevention of restenosis.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method for therapeutic treatment of a body passageway, including the steps of: (a) implanting a marker in the passageway; and (b) irradiating the marker from outside the passageway.
According to the present invention there is provided an apparatus for stereotactic radiotreatment of a moving target in a patient, including: (a) a mechanism for tracking the target; and (b) a mechanism for directing a beam of ionizing radiation at the target from outside the patient and in accordance with the tracking.
The scope of the present invention includes external irradiation of any moving target, within a patient, that can be marked by implanting, in a body passageway of the patient, a marker that can be imaged by non-invasive physical means, such as electromagnetic radiation (for example, x-rays or infrared radiation), ultrasound, or external detection of a source of low level radiation on the marker itself. The marker may be a stent, a coil, or any other foreign object; or radioactively labeled tissue. The body passageways included in the scope of the present invention include all body passageways that exhibit motion, whether periodic or irregular, rapid or slow, that prevents the application of conventional stereotactic radiotreatment. Among these body passageways are the vessels of the circulatory system, the gastrointestinal tract and the genitourinary tract. The radiation directed at the marker from outside the patient may be any suitable ionizing radiation, including gamma radiation and x-rays.
Nevertheless, the primary focus of the present invention is on the treatment or prevention of restenosis in a coronary artery. In this application, the present invention exploits the fact that the stent, being made of metal, is significantly more opaque to external irradiation such as x-rays or ultrasound than the surrounding tissue. The moving stent is tracked, using fluoroscopy, and ionizing radiation, typically gamma radiation, is aimed at the stent as the stent moves. This tracking is made easier by the fact that the motion of the stent is periodic, being determined by the cardiac cycle. According to one embodiment of the present invention, described in detail below, the irradiation is synchronized with a particular point in the cardiac cycle. According to another embodiment, the ionizing radiation is aimed at the stent as the stent moves.
The irradiation may be performed hours or days after implanting the stent, for prevention of restenosis, or weeks or months after implanting the stent, for treatment of restenosis, and may be fractionated.
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patent: 5538494 (1996-07-01), Matsuda
patent: 5879281 (1999-03-01), Ein-Gal
patent: 6001054 (1999-12-01), Regulla et al.
patent: 6006126 (1999-12-01), Cosman
Mosseri Morris
Weshler Zeev
Friedman Mark M.
Hadasit Medical Research Services and Development Company Ltd.
Lacyk John P.
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