News Column

Patent Issued for Method for Radiation Sterilization of Medical Devices

May 13, 2014



By a News Reporter-Staff News Editor at Life Science Weekly -- A patent by the inventors Freeman, Abigail (Del Mar, CA); Simmons, Gregory S. (Newport Beach, CA); Riggs, Brian D. (Phoenix, AZ); Harrison, Robert (Fallbrook, CA); Castro, Dan (Santa Clara, CA); Huang, Bin (Pleasanton, CA), filed on August 21, 2013, was published online on April 29, 2014, according to news reporting originating from Alexandria, Virginia, by NewsRx correspondents (see also Abbott Cardiovascular Systems Inc.).

Patent number 8709340 is assigned to Abbott Cardiovascular Systems Inc. (Santa Clara, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "This invention relates to radiation sterilization.

"This invention relates to radially expandable endoprostheses, which are adapted to be implanted in a bodily lumen. An 'endoprosthesis' corresponds to an artificial device that is placed inside the body. A 'lumen' refers to a cavity of a tubular organ such as a blood vessel.

"A stent is an example of such an endoprosthesis. Stents are generally cylindrically shaped devices, which function to hold open and sometimes expand a segment of a blood vessel or other anatomical lumen such as urinary tracts and bile ducts. Stents are often used in the treatment of atherosclerotic stenosis in blood vessels. 'Stenosis' refers to a narrowing or constriction of the diameter of a bodily passage or orifice. In such treatments, stents reinforce body vessels and prevent restenosis following angioplasty in the vascular system. 'Restenosis' refers to the reoccurrence of stenosis in a blood vessel or heart valve after it has been treated (as by balloon angioplasty, stenting, or valvuloplasty) with apparent success.

"The treatment of a diseased site or lesion with a stent involves both delivery and deployment of the stent. 'Delivery' refers to introducing and transporting the stent through a bodily lumen to a region, such as a lesion, in a vessel that requires treatment. 'Deployment' corresponds to the expanding of the stent within the lumen at the treatment region. Delivery and deployment of a stent are accomplished by positioning the stent about one end of a catheter, inserting the end of the catheter through the skin into a bodily lumen, advancing the catheter in the bodily lumen to a desired treatment location, expanding the stent at the treatment location, and removing the catheter from the lumen.

"In the case of a balloon expandable stent, the stent is mounted about a balloon disposed on the catheter. Mounting the stent typically involves compressing or crimping the stent onto the balloon. The stent is then expanded by inflating the balloon. The balloon may then be deflated and the catheter withdrawn. In the case of a self-expanding stent, the stent may be secured to the catheter via a retractable sheath or a sock. When the stent is in a desired bodily location, the sheath may be withdrawn which allows the stent to self-expand.

"The stent must be able to satisfy a number of mechanical requirements. First, the stent must be capable of withstanding the structural loads, namely radial compressive forces, imposed on the stent as it supports the walls of a vessel. Therefore, a stent must possess adequate radial strength. Radial strength, which is the ability of a stent to resist radial compressive forces, is due to strength and rigidity around a circumferential direction of the stent. Radial strength and rigidity, therefore, may also be described as, hoop or circumferential strength and rigidity.

"Once expanded, the stent must adequately maintain its size and shape throughout its service life despite the various forces that may come to bear on it, including the cyclic loading induced by the beating heart. For example, a radially directed force may tend to cause a stent to recoil inward. Generally, it is desirable to minimize recoil.

"In addition, the stent must possess sufficient flexibility to allow for crimping, expansion, and cyclic loading. Longitudinal flexibility is important to allow the stent to be maneuvered through a tortuous vascular path and to enable it to conform to a deployment site that may not be linear or may be subject to flexure. Finally, the stent must be biocompatible so as not to trigger any adverse vascular responses.

"The structure of a stent is typically composed of scaffolding that includes a pattern or network of interconnecting structural elements often referred to in the art as struts or bar arms. The scaffolding can be formed from wires, tubes, or sheets of material rolled into a cylindrical shape. The scaffolding is designed so that the stent can be radially compressed (to allow crimping) and radially expanded (to allow deployment). A conventional stent is allowed to expand and contract through movement of individual structural elements of a pattern with respect to each other.

"Additionally, a medicated stent may be fabricated by coating the surface of either a metallic or polymeric scaffolding with a polymeric carrier that includes an active or bioactive agent or drug. Polymeric scaffolding may also serve as a carrier of an active agent or drug.

"After a stent is fabricated, a stent typically undergoes sterilization to reduce the bioburden of the stent to an acceptable sterility assurance level (SAL). There are numerous methods of sterilizing medical devices such as stents, the most common being ethylene oxide treatment and treatment with ionization radiation such as electron beam and gamma radiation. Generally, it is desirable for the sterilization procedure to have little or no adverse affects on the material properties of the stent."

In addition to the background information obtained for this patent, NewsRx journalists also obtained the inventors' summary information for this patent: "Various embodiments of the present invention include a method of sterilizing a stent delivery assembly comprising: exposing a stent delivery assembly to radiation from a radiation source, wherein a covering over a selected section of the assembly selectively modifies the radiation from the radiation source that is delivered to the selected section of the assembly.

"Further embodiments of the present invention include a method of sterilizing a stent delivery assembly comprising: exposing a stent delivery assembly enclosed in a package to radiation from a radiation source, wherein the package comprises one or more modifier sections, the modifier sections selectively modify the radiation from the radiation source that is delivered to the selected section of the assembly.

"Additional embodiments of the present invention include a system for sterilizing a stent delivery assembly with radiation, comprising: a stent delivery assembly; and a package having a one or more modifier sections, the assembly being disposed within the package, wherein the one or more modifier sections are positioned relative to a selected section of the assembly to modify radiation delivered to the selected section of the assembly when radiation is directed at the assembly from a radiation source.

"Other embodiments of the present invention include a system for sterilizing a stent delivery assembly with radiation, comprising: a stent delivery assembly; and a covering over a selected section of the assembly, wherein the covering modifies radiation delivered to the selected section of the assembly when radiation is directed at the assembly from a radiation source.

"Certain additional embodiments of the present invention include a method of sterilizing a stent delivery assembly comprising: exposing a stent delivery assembly to radiation from a radiation source, the assembly being disposed in a package supported by a fixture, wherein a modifier section of the fixture selectively modifies the radiation from the radiation source that is delivered to a selected section of the assembly.

"Some other embodiments of the present invention include a method of sterilizing a plurality of stent delivery system assemblies with a radiation source, the method comprising: positioning a plurality of stent catheter assemblies within packages supported on a fixture, each of the assemblies arranged in a planar configuration in the packages; and exposing the assemblies to a radiation beam from a radiation source, the beam being at an acute angle to the planar configuration of the packages that are positioned between the source and the fixture, wherein the packages are arranged such that the radiation passes through more than one of the assemblies during exposure, the delivered dose varying with distance between the radiation source and the fixture, one or more of the assemblies being positioned within the packages so that a selected section of the assemblies receives a selected delivered radiation dose."

URL and more information on this patent, see: Freeman, Abigail; Simmons, Gregory S.; Riggs, Brian D.; Harrison, Robert; Castro, Dan; Huang, Bin. Method for Radiation Sterilization of Medical Devices. U.S. Patent Number 8709340, filed August 21, 2013, and published online on April 29, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=98&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=4873&f=G&l=50&co1=AND&d=PTXT&s1=20140429.PD.&OS=ISD/20140429&RS=ISD/20140429

Keywords for this news article include: Sterilization, Infection Control, Abbott Cardiovascular Systems Inc..

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Life Science Weekly


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