Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
1998-03-31
2001-07-31
Lacyk, John P. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
C600S001000
Reexamination Certificate
active
06267717
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for treating a body structure with radiation and, in particular, an apparatus and method for treating a body structure with a radioactive material having a short half-life.
BACKGROUND OF THE INVENTION
As an alternative to vascular surgery, balloon angioplasty has become a common method for unblocking narrowed or occluded blood vessels. In this procedure, an angioplasty balloon is inflated within a stenosed vessel in order to dilate the vessel to provide an enlarged lumen. Although balloon angioplasty has been successful in restoring flow in stenotic or occluded vessels, these vessels often restenose due to excessive neointima formation, inward vessel remodeling, and elastic recoil of the diseased tissue. It has been determined that restenosis after coronary balloon angioplasty requires additional treatment in about 35-40% of treated lesions. Although various pharmacological, mechanical, and radiological methods have been utilized, the rate of restenosis has continued to be unacceptably high.
Recently, it was shown in a porcine model that post angioplasty irradiation of the vessel effectively reduced the restenotic response following an experimentally induced coronary overstretch lesion. The attention to date has been focused on gamma ray (e.g.,
192
Ir and
125
I) and beta particle (e.g.,
32
p,
89
Sr-
90
Y, and
131
I) emitting radioisotopes. The relatively long half-lives of those species mean that the species can be conveniently produced off-site and then transported to the particular institution where the treatment is to occur.
One approach for treating a vessel with radiation to prevent restenosis has been to use radioactive materials in solid form, such as radioactive seeds, coils, or wires. The radioactive materials are enclosed by a catheter and, accordingly, do not come in contact with the patient's blood, thereby eliminating the risk of inadvertently releasing the radioactive material into the patient's blood stream. When gamma ray and beta particle emitters are used, the radiotoxicity associated with direct contact between the radioactive material and the patient's blood stream stems from the very long physical half-lives of these species, as well as from the fact that these emitters tend to accumulate in critical organs like the bone marrow. Further, the use of radioactive materials in solid, as opposed to liquid, form minimizes the shut-down period required to adequately decontaminate a laboratory in the event that the radioactive material escapes from the catheter. However, the radiation source in the proposed devices is difficult to center within the body structure being treated. Accurate centering of the radiation source is required to insure equal dosing along the length and circumference of the body structure being treated. Accordingly, such devices suffer from the disadvantage of over dosing some sections of the body structure being treated and under dosing other sections.
A second approach has been to use a radiation source in liquid form wherein the liquid is contained within an angioplasty balloon positioned within the body structure being treated. However, a rupture of the balloon would release the radioactive liquid directly into the patient's blood stream. Since balloon failure is believed to occur in about 0.1% of cases, special precautions must be taken to minimize the risk of whole-body exposure in the event of a balloon rupture. Towards that end, the use of balloon catheters with multiple wall layers has been proposed. In these devices, a second wall layer would contain the radioisotope in case one layer ruptured. However, these devices have a complicated structure, are expensive to manufacture, and have thicker front profiles making them more difficult to handle.
In light of the foregoing, it would be highly advantageous to provide a system and method for treating a body structure with radiation wherein the system and method minimize the risk of whole-body exposure to radiation under all circumstances for both the patient and the staff. Towards that end, the system and method preferably utilizes a radioactive material having a relatively short half-life (e.g., less than about 2 days). Preferably, the system should comprise means for cheaply and conveniently producing the radiation as close to the time of use as is practical. In addition, the system should be able to provide a therapeutic dose of radiation uniformly along the entire length and circumference of the body structure being treated in a reasonable amount of time (e.g., about 2-5 minutes). Further, the system should provide means for safely and easily handling the radioactive material, dosing the patient, and disposing of the radioactive material.
SUMMARY OF THE INVENTION
The present invention relates to an apparatus for treating a body structure with radiation. The apparatus serves four primary functions. First, the apparatus enables a user to transport a liquid radioactive material directly from a radioisotope generator to a treatment device, such as a balloon catheter. Accordingly, use of the apparatus minimizes the extent to which the radioactive material must be handled, the potential for error, and the likelihood of contamination. Second, the apparatus minimizes the user's risk of exposure to radiation. Third, the apparatus can be used to insure that the correct dose of radiation is applied to the body structure. And fourth, the apparatus can be used to concentrate the radioactive material in a solution having a volume which matches the volume of the balloon being used.
In one embodiment, the apparatus in accordance with the present invention comprises a concentrator for receiving a first solution comprising the radioactive material and for producing a second, more concentrated radioactive solution comprising the radioactive material. The concentrator functions to insure that the volume of the second solution is less than the volume of the first solution. Accordingly, the volume of the second solution can be adjusted to match the volume of the balloon used to treat the body structure.
In one particular embodiment, the concentrator comprises a cartridge having a first open end, a second open end, and a hollow cavity formed between the first and second open ends. The cartridge is provided with a first inlet for introducing the first solution into the cavity through the first open end of the cartridge. Towards that end, the concentrator can be operatively connected with a radioisotope generator which produces the first solution. The generator may be a parent-daughter radioisotope generator, such as those available for the production of
68
Ga or
188
Re. Alternatively, the generator may be a cyclotron for the production of
11
C,
13
N,
18
F, or
15
O. By connecting the concentrator to the generator, the solution can be transferred from the generator to the concentrator with a minimal risk of leakage.
A separating medium may be contained within the cavity of the cartridge within the concentrator. The separating medium comprises a material, such as an ion-exchange resin, which selectively bonds to the radioactive material and not the solute in which the radioactive material is dissolved. The apparatus further comprises a syringe for flushing the separating medium with an elution fluid.
The apparatus may also comprise a calibrator, operatively associated with the concentrator, for measuring a level of radiation associated with the radioactive material. For example, the calibrator may comprise means for directly measuring the level of radiation, such as a Geiger-Muller counter, or means for indirectly measuring the level of radiation, such as a scintillation counter.
In addition, the apparatus comprises a delivery unit for connecting the apparatus to a dosing device having a balloon, such as a balloon catheter and guide wire assembly. The delivery unit comprises a fluid conduit having a first inlet operatively connected to the concentrator for receiving the second, more concentrated
Hutchins Gary
March Keith L.
Stoll Hans-Peter
Advanced Research & Technology Institute
Dann, Dorfman, Herrell, Herrell, P.C.
Lacyk John P.
LandOfFree
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