Radiant energy – Radiation controlling means – Shielded receptacles for radioactive sources
Reexamination Certificate
2002-10-29
2003-11-18
Lee, John R. (Department: 2881)
Radiant energy
Radiation controlling means
Shielded receptacles for radioactive sources
C250S505100, C250S515100
Reexamination Certificate
active
06649922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates, generally, to the art of packaging. More particularly, it relates to a packaging system and method for shielding items that emit radiation.
2. Description of the prior art
U.S. Pat. No. 3,845,316 discloses a coated lead foil for protecting photographic film from X-ray machines. If a pinhole is formed in such a package, the likelihood of radiation from an X-ray machine entering into the interior of the package through said pinhole and damaging the film is quite remote. Thus, such packaging adequately protects film from X-rays.
However, if the film is replaced by a source of radiation, the presence of a pinhole becomes unacceptable because radiation is likely to travel through the pinhole and expose the handlers of the package to radiation. Thus, the known packaging is inadequate to protect handlers of the package from X-rays that originate from within the package.
The peripheral edges of conventional lead foil packages are heat sealed and are flat, i.e., the edges lie in the same plane as the main body of the package. A source of radiation emits radiation in all directions. Accordingly, some radiation will travel in a straight line that is parallel to the top and bottom panels of such packages, and pass through the flat edges into the ambient environment through the heat seal. The plastic that seals the edges of the package offers insignificant resistance to radiation passing therethrough.
Many surgical supplies such as sutures, specialty items, and the like are delivered to hospitals in special packaging. These packages keep sterile items sterile and enable such items to be used immediately upon removal from the packaging, there being no need to undergo preparatory steps after opening the packaging. Typically, a package of this type is made by laminating a standard lead foil to plastic and sealing the package to form a pouch.
Items that are sources of nuclear radiation, however, are not delivered in such packages because of the above-noted pinhole problem and because the flat, heat-sealed edges of such packages would enable radiation to escape into the environment as above-noted. The slightest defect in packaging is unacceptable for such items. Instead, radioactive items are delivered in specially shielded containers. Various designs have been created to enable the person opening such a shielded container to transfer its contents quickly to a shielded tool or other device that uses the radioactive material.
For example, radioactive brachytherapy seeds are usually sent to hospitals in non-sterile vials within which the seeds are loosely contained. Upon receipt of such vials, the hospital staff needs to autoclave the seeds to sterilize them. Someone must then deliver the seeds to the operating room. The seeds are loaded into needles in the operating room where they are implanted into the cancerous prostate gland of a patient, for example.
It would be advantageous if radioactive materials could be delivered in sterile condition in packages similar to the packages used to deliver non-radioactive items. An improved packaging system would obviate the need for the shielded containers and devices for transferring radioactive items from such shielded containers to the tools within which they are used. It would also eliminate the need for the recipient of the package to sterilize the contents of the package.
Moreover, if a package could be provided that would eliminate the radiation-leakage problem, then the radioactive materials could be sterilized and packaged at a central location, thereby reducing the amount of operating room time spent on such tasks.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.
SUMMARY OF THE INVENTION
The long-standing but heretofore unfulfilled need for a shielded packaging system is now met by a new, useful, and nonobvious shielded packaging system formed by securing to one another a pair of abutting panels about their respective peripheries. A first panel includes a first layer of plastic, a first layer of lead foil, and a first layer of adhesive disposed between the first layer of plastic and the first layer of lead foil. The first panel further includes a second layer of lead foil, a second layer of adhesive disposed between the first layer of lead foil and the second layer of lead foil, a second layer of plastic, and a third layer of adhesive disposed between the second layer of lead foil and the second layer of plastic. Each of the layers is collectively positioned in a common, substantially flat plane.
The second panel has the same construction as the first panel and the panels are joined to one another about a predetermined extent of their respective peripheral edges so that an opening is defined where the respective peripheral edges are not joined to one another. Radioactive materials are thus inserted into the package through the opening and the opening is then closed.
Each panel of the shielded packaging system includes at least two layers of lead foil so that a pinhole that might be formed in the first layer of lead foil is unlikely to be in alignment with a pinhole that might be formed in the second layer of lead foil.
The respective peripheral edges of the first and second layers of lead foil of each panel are offset relative to the substantially flat plane of the packaging system so that radiation traveling in a straight line parallel to the substantially flat plane cannot escape into an ambient environment through the respective peripheral edges.
More particularly, a fold is formed in the shielded packaging system to close the opening. The fold is formed in at least two layers of lead foil of each panel so that radiation traveling in a straight line parallel to the substantially flat plane cannot escape into an ambient environment through the fold.
The first and second layers of plastic are made of a flame retardant, heat-sealable plastic, preferably polyvinylchloride. The first and second layers of plastic preferably have a thickness of about 0.0035 inch.
The first and second layers of lead foil have a thickness of at least about 0.005 inch.
The steps of the novel method for sealing radioactive items in a container include the steps of providing a first panel including a first layer of plastic, providing a first layer of lead foil, positioning a first layer of adhesive between the first layer of plastic and the first layer of lead foil, providing a second layer of lead foil, positioning a second layer of adhesive between the first layer of lead foil and the second layer of lead foil, providing a second layer of plastic, positioning a third layer of adhesive between the second layer of lead foil and the second layer of plastic, and positioning the layers collectively in a common, substantially flat plane to form a first panel.
The second panel is made in the same way and the first and second panels are joined to one another about a predetermined extent of their respective peripheral edges so that an opening is defined where the respective peripheral edges are not joined to one another and so that a pinhole that might be formed in a first layer of lead foil is unlikely to be in alignment with a pinhole that might be formed in a second layer of lead foil.
The novel method further includes the step of offsetting the respective peripheral edges of the first and second layers of lead foil of each panel relative to the substantially flat plane of the packaging system so that radiation traveling in a straight line parallel to the substantially flat plane cannot escape into an ambient environment through the respective peripheral edges.
The offsetting step is performed by forming a fold in the shielded packaging system to close the opening. The fold is formed in the at least two layers of lead foil of each panel so that radiation traveling in a straight line parallel to said substantially flat plane cannot escape
Gurzo Paul M.
Lee John R.
Miller Stanley M.
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