Surgery – Radioactive substance applied to body for therapy – Radioactive substance placed within body
Reexamination Certificate
1999-08-06
2001-10-16
Lacyk, John P. (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
Radioactive substance placed within body
Reexamination Certificate
active
06302839
ABSTRACT:
TECHNICAL FIELD
The technical field relates generally to the use of radiation therapy after an angioplasty procedure, to minimize the occurrence of restenosis and, more particularly, to a device and method for delivering a radio isotope to a stenotic region, e.g., in liquid or gaseous form, to inhibit restenosis.
DESCRIPTION OF THE RELATED ART
A common treatment for blockage or stenosis of the arteries is a procedure known as percutaneous transluminal angioplasty (PTA) and, when utilized within the coronary artery, is known as percutaneous transluminal coronary angioplasty (PTCA). During this procedure, the location of a stenotic constriction or blockage within the coronary artery is identified and a guide wire is advanced through the vascular system to a point distal to or beyond the blockage. Subsequently, an angioplasty catheter in one form having an inflatable angioplasty dilatation balloon at a distal end thereof or in a second form an atherectomy catheter, or a stent delivery catheter, is advanced along the guide wire until the balloon is located at the point of constriction. The balloon is then repeatedly inflated and deflated to open the constriction by compressing the plaque against the vessel walls. In this manner, a constriction within the vascular system may be opened to allow increased blood flow. Similarly, the plaque can be removed by atherectomy, or the plaque can be scaffolded by placing a stent.
The vascular tissue may respond to the trauma by proliferative growth of cells responsible for restenosis, e.g., smooth muscle tissue cells, deposition of extracellular matrix material. Upon increased growth of such cells, the formerly constricted area may become reconstricted or narrowed down, which is commonly referred to as “restenosis.” This can occur any time from within a few weeks to several years following the original angioplasty procedure, thus, often necessitating repeated angioplasty procedures to reopen the constriction. Other causes of restenosis have been reported including, but not limited to, elastic recoil of the vessel wall and focal shrinkage of the vessel wall, commonly referred to as “negative remodelling.”
It has been found that by exposing the vascular tissues to radiation subsequent to the balloon angioplasty procedure, the proliferative growth of the smooth muscle cells and/or vessel shrinkage responsible for restenosis is inhibited. However, difficulty in providing uniform radiation to the surrounding tissue may arise. Often, after expansion of a constricted area by a balloon angioplasty procedure, the resulting relatively unconstricted area has a generally asymmetrical cross-section. The asymmetrical cross-section may pose problems for those devices which are configured to position a radioactive source substantially at the center of the vascular structure. Thus, it would be desirable to have a device and method for delivering a radioactive dose in a substantially uniform manner to the site of a vascular constriction post-angioplasty.
SUMMARY
There is provided a device and a method of irradiating vascular tissues which have been subjected to a balloon angioplasty procedure. The device generally includes a balloon catheter having an expandable balloon which can be positioned over a guide wire within the vascular tissue, a transfer device for transferring radioactive material, e.g., fluid, from the transfer device to the balloon and an inflation device for forcing the radioactive fluid out of the transfer device and into the balloon. The balloon catheter includes an inflation lumen extending from an interior of the balloon through the catheter to a proximal portion of the catheter. The balloon catheter also includes a guide wire lumen. The guide wire lumen may extend the entire length of the catheter from its distal to its proximal end or may extend from the distal end to a point just proximal of the balloon. The transfer device includes first and second chambers which are separated by a movable piston or membrane. The first chamber is configured to receive a fluid to move the piston within the transfer device while the second chamber is configured to receive, retain and shield or isolate the radioactive fluid prior to injection into the balloon catheter. The inflation device provides a fluid, preferably saline, to the first chamber to move the piston by creating a positive or negative gauge pressure in the first chamber. Preferably, The inflation device may include a pressure gauge as well as an overpressure relief valve. As used herein, the term “radioactive fluid” is intended to encompass liquids, gases, solids and/or combinations thereof.
A mounting block may also be provided to connect the second chamber of the transfer device to the inflation lumen of the balloon catheter. Specifically, the mounting block retains the proximal end of the balloon catheter with the inflation lumen in fluid communication with the second isotope containing chamber in the mounting block. The mounting block includes an injection port having a self-sealing septum which is in fluid communication with the second isotope containing chamber.
In one embodiment, the mounting block is interlocked to the proximal end of the balloon catheter by use of a bayonet style fitting. It is further contemplated that other interlocking optical, mechanical and/or electrical features and/or structures may be provided, and may include recognition features to ensure that only a catheter suitable for radiation therapy is coupled to the transfer device. Moreover, such recognition features and/or structures may provide information to an associated system to identify to the system characteristics of the catheter, e.g., catheter length and size, capacity, etc., which may be used in controlling the transfer device to assure transfer of an appropriate quantity of isotope containing material to the balloon catheter. The system may calculate, display and/or control treatment time and dose delivery and may monitor system integrity, e.g., using fluid pressure sensors in the catheter, second chamber or mounting block.
The transfer device includes an injection needle which extends from the second chamber and is provided to pierce self-sealing septum in order to draw and inject the radioactive fluid through the self-sealing septum. Preferably, the injection needle is provided with an elastomeric boot surrounding the needle which acts as a seal against the septum. The transfer device may also be provided with a needle shield extending from the second chamber and surrounding the injection needle. The transfer device may be connected to the mounting block by suitable means such as a bayonet style mounting fixture.
There may also be provided a separate source or container for the radioactive fluid which also has a self-sealing septum. The source will also include a bayonet style mounting fixture for affixing to the transfer device in order to load the transfer device with the radioactive fluid. Additionally, an aspiration syringe may be provided having a needle to pierce the septum of the mounting block in order to draw air out of the balloon and inflation lumen of the balloon catheter to create a vacuum therein.
There is also disclosed a method for irradiating vascular tissues which includes providing a transfer device having first and second chambers and a piston movably disposed within the chambers, an inflation device for moving the piston within the first and second chambers and a balloon catheter for carrying a radioactive fluid from the second chamber of the transfer device to a balloon on a distal end of the balloon catheter. The method includes loading radioactive fluid into the second chamber of the transfer device, positioning the balloon at a stenotic region within the vascular system, attaching the transfer device to a proximal portion of the balloon and attaching an inflation device to the transfer device such that the inflation device can force fluid into the first chamber of the transfer device. The method further includes forcing fluid from the inflation device into the transfer devic
Chernomorsky Ary S.
Jackson Jerome
Schmidlen Robert L.
Burns Doane Swecker & Mathis L.L.P.
Calmedica, LLC
Lacyk John P.
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