Patent Application
20110165373
The present invention relates generally to radio-opaque films and, more specifically, to radio-opaque films of laminate construction. More specifically, the present invention relates to films in which one or more layers of particulate radio-opaque material are trapped between two containment layers.
Modern imaging technologies, such as x-ray, fluoroscopy, and computer tomography (CT), all of which employ ionizing radiation (e.g., x-rays, etc.), have revolutionized diagnostic radiology. The benefits of using imaging technologies are many: living tissues can be non-invasively visualized; radiographic techniques may now be used to diagnose conditions that were once identified with laparoscopic techniques; and diagnosis with radiography is noninvasive, fast and painless. As a result, by one estimate, in 2008 over 178 million x-rays were performed in the United States alone. Over 19,500 CT scans are performed in the United States each day, subjecting each patient to the equivalent of between 30 to about 500 chest radiographs per scan. Annually, about four million CT scans are performed on children. In fact, the United States accounts for half of the most advanced procedures that use ionizing radiation.
Unfortunately, the increase in the use of radiographic procedures comes with a downside: the average American gets the highest per capita dosage of ionizing radiation in the world, with the average dose growing six-fold over the last couple of decades. With the increase in exposure to ionizing radiation comes an increased risk of long term damage (e.g., cancer, genetic damage that may affect future generations, etc.) to the individuals who have been exposed to radiation. The risk of radiation-induced damage is particularly prevalent among health care professionals who are repeatedly exposed to ionizing radiation, either directly or incidentally.
Recognition of the potentially grave effects of repeated exposure to ionizing radiation has lead to the development of radiation-blocking garments. Traditionally, radiation-blocking garments have been manufactured by dispersing lead (Pb) powder throughout polymeric materials, such as rubber and other elastomeric matrices. Since the lead particles are dispersed throughout a polymer matrix, in order to provide a desired level of radiation attenuation, the resulting composite must be relatively thick and cumbersome. It is also heavy, causing discomfort to clinicians who require protection for several hours in a typical day, and are known to lead to problems such as fatigue or back pain.
While the use of thinner lead sheets or foils could provide comparable radiation protection with less weight, they lack the pliability needed for use in garments.
The use of materials than lead, in conjunction with polymeric matrices, to attenuate ionizing radiation has resulted in some weight savings. Nonetheless, lead-free composites are even bulkier than lead-based composites, providing only insignificant weight savings, and typically offer less protection from ionizing radiation than lead-based composites.
The present invention includes various embodiments of radio-opaque films. A radio-opaque film of the present invention includes at least one layer of radio-opaque material between a pair of containment layers. The radio-opaque layer may comprise particles of radio-opaque material and a binder, which holds the particles of radio-opaque material together. When held between two pliable containment layers, the radio-opaque layer may also be pliable.
The radio-opaque material may comprise a non-toxic material. The radio-opaque material may comprise an elemental species having an atomic number of 52 or greater. Examples of such elemental species include, but are not limited to, barium, bismuth and lanthanum. In some embodiments, the radio-opaque material may comprise a salt (e.g., barium sulfate, bismuth oxide, etc.).
Some embodiments of radio-opaque films of the present invention include two or more radio-opaque layers. In such embodiments, adjacent layers may include different radio-opaque materials. Layers with different radio-opaque material may be organized to optimize attenuation of ionizing radiation while minimizing the overall thickness of the radio-opaque film.
Methods for manufacturing radio-opaque films are also within the scope of the present invention. In such a method, a radio-opaque material may be deposited onto a surface of a first containment layer, a second containment layer may be disposed over the radio-opaque material, and the first and second containment layers may be secured to one another, capturing the radio-opaque material therebetween. A binder that holds particles of the radio-opaque material together may also adhere to the first and second containment layers and, thus secure the first and second containment layers to one another.
Garments and other apparatus that are made, at least in part, from a radio-opaque film that incorporates teachings of the present invention are also within the scope of the present invention.
Other aspects, as well as features and advantages of various aspects, of the present invention will become apparent to those of ordinary skill in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims.
In the drawings:
The graph of
The present invention includes radio-opaque films, which may be used in a number of different ways. Without limiting the scope of the present invention, a radio-opaque film of the present invention may be used as a surgical drape, in shields and protective devices that provide an individual with protection from ionizing radiation, in garments that are worn by a healthcare provider (e.g., a doctor, a physician's assistant, a nurse, a technician, etc.) during a procedure (e.g., a surgical procedure, etc.) in which the healthcare provider may be exposed to ionizing radiation, and in radiation shielding curtains. Various embodiments of radio-opaque films that incorporation teachings of the present invention are shown in
In
In some embodiments, one or both containment layers 20 and 30 may include at least one surface with features, such as patterned or random texturing, that increase its effective surface area and/or enhance adhesion between that containment layer 20, 30 and the adjacent radio-opaque layer 40.
By way of example, and not by way of limitation, each containment layer 20 and 30 may have a thickness of about 15 mils (0.015 inch, or about 0.375 mm) or less. Of course, embodiments of radio-opaque films 10 that include containment layers 20, 30 of other thicknesses are also within the scope of the present invention.
A variety of different materials are suitable for use as containment layers, including, without limitation, polymers, papers, and fabrics. The material used as each containment layer 20, 30 may be selected on the basis of a number of factors, including, without limitation, the porosity of the material, water-resistance (which may be a function of porosity, the material itself, etc.), bacterial resistance (which may be a function of porosity, incorporation of antibacterial agents into the material, etc.), flexibility, feel, and any other factors. In some embodiments, each containment layer 20, 30 may comprise a polymer or a polymer-based material. More specifically, one or both containment layers 20, 30 may comprise a polymer film or a sheet of woven or non woven polymer fibers with paper-like or fabric-like characteristics. In other embodiments, one or both containment layers 20, 30 may comprise a polymer, but have a structure (e.g., fibers arranged in a way) that resembles paper (e.g., for use as a surgical drape, etc.) or fabric (e.g., for use in a gown, etc.).
In some embodiments, one or both of the containment layers may have some opacity to ionizing radiation, or radio-opacity.
The radio-opaque layer 40 of a radio-opaque film 10 of the present invention includes a material that attenuates ionizing radiation, or a radio-opaque material. In some embodiments, the radio-opaque material of the radio-opaque layer 40 may be in a particulate or powdered form. In such embodiments, the radio-opaque layer 40 may include a binder that holds particles of the radio-opaque material together.
The radio-opaque material may be non-toxic. In various embodiments, the radio-opaque material may comprise or be based upon elemental species having atomic numbers of 56 or greater. Non-limiting examples of such elemental species include barium species, bismuth species and lanthanum species. In some embodiments, the radio-opaque material may comprise an inorganic salt. Non-limiting examples of non-toxic, radio-opaque inorganic salts include barium sulfate and bismuth oxide.
In embodiments where the radio-opaque layer 40 includes a binder, any material that will hold particles of the radio-opaque material together without causing a substantial decrease in the density of the radio-opaque material may be used as the binder. The binder may hold particles of radio-opaque material together loosely, it may provide a stronger bond between adjacent particles, and/or it may enable the formation of a smooth uniform coating, or film. Examples of such materials include, but are not limited to, polyvinyl alcohol (PVA), polyvinyl butyrol (PVB), polyethylene glycol (PEG), glycerine, capric triglyceride, cetyl alcohol, glyceryl sterate and combinations of any of these materials.
In a radio-opaque layer 40 with particles of radio-opaque material held together with a binder, the radio-opaque material may, in some embodiments, comprise at least about 50% of the weight of the radio-opaque layer 40, with the binder comprising about 50% or less of the weight of the radio-opaque layer 40. Other embodiments of radio-opaque layers 40 include about 75% or more of the radio-opaque material, by weight, and about 25% or less of the binder, by weight. In still other embodiments, the radio-opaque material may comprise about 97% or more of the weight of the radio-opaque layer 40, while the binder comprises only up to about 3% of the weight of the radio-opaque layer 40.
In some embodiments, a radio-opaque layer 40 of a radio-opaque film 10 of the present invention has a thickness of about 40 mils (0.040 inch, or 1 mm) or less. In other embodiments, a radio-opaque film 10 may include a radio-opaque layer 40 with a thickness of about 25 mils (0.020 inch, or about 0.6 mm) or less. In still other embodiments, the radio-opaque layer 40 of a radio-opaque film 10 may have a thickness of about 15 mils (0.015 inch, or about 0.375 mm) or less, about 10 mils (0.010 inch, or about 0.25 mm) or less, or about 5 mils (0.005 inch, or about 0.125 mm) or less.
The ability of the radio-opaque layer 40 to attenuate ionizing radiation depends upon a number of factors, including, without limitation, the attenuating ability of each radio-opaque material from which the radio-opaque layer 40 is formed, the relative amounts of radio-opaque material and binder in the radio-opaque layer 40, and the thickness of the radio-opaque layer 40.
The containment layers 20 and 30 may be secured to the radio-opaque layer 40, and to one another, in a number of different ways. As an example, in embodiments where the radio-opaque layer 40 includes a particulate or powdered radio-opaque material and a binder, the binder may adhere or otherwise secure the containment layers 20 and 30 to the radio-opaque layer 40 and, thus, to one another. In other embodiments, the containment layers 20 and 30 may be directly or indirectly secured to one another at a plurality of spaced apart locations (e.g., in a matrix of spaced apart points, a grid of spaced apart row lines and column lines, etc.) with the radio-opaque layer 40 occupying substantially all other areas (i.e., substantially all of the area) between the containment layers 20 and 30. For example, the containment layers 20 and 30 may be directly fused to one another (e.g., by thermal bonding, solvent bonding, etc.). As another example, adhesive material may be disposed between a plurality of spaced apart locations on the containment layers 20 and 30.
Known processes may be used to manufacture a radio-opaque film 10 that embodies teachings of the present invention. In some embodiments, the radio-opaque material and binder may substantially homogeneously mixed in a solvent. The solvent may comprise a carrier solvent within which the binder is provided, or a separately added solvent. In more specific embodiments, the resulting slurry may have a solids content, or solids loading, of about 75% w/w to about 80% w/w. The slurry may then be applied to one of the containment layers 20 in a manner that will result in the formation of a thin film of radio-opaque material over the containment layer 20. In specific embodiments, a doctor blade or simulated doctor blade technique may be employed to form the radio-opaque layer 40. In other embodiments one or more rollers may be employed to form and disperse the radio-opaque layer 40 between the containment layers 20 and 30. The other containment layer 30 may then be applied over the radio-opaque layer 40. In a specific embodiment suitable for mass production, roll calendaring techniques may be used.
Turning now to
The use of multiple sublayers 42′, 44′, etc., may provide a radio-opaque layer 40′ an increased attenuation over the use of a single layer of radio-opaque material of the same thickness as radio-opaque layer 40′. When superimposed sublayers 42′, 44′, etc., of different radio-opaque materials are used, selection of the radio-opaque material for each sublayer 42′, 44′ may be based upon the arrangements of their attenuating species (e.g., lattice structures, the distances their attenuating species are spaced apart from one another, etc.), as sublayers 42′ and 44′ with differently arranged attenuating species may attenuate ionizing radiation differently. The material or materials of each sublayer 42′, 44′ may be selected on the basis of their ability to attenuate ionizing radiation over different bandwidths (or ranges) of frequencies or wavelengths, which may impart the radio-opaque layer 40′ with the ability to attenuate a broader bandwidth of frequencies of ionizing radiation than the use of a single layer of radio-opaque material that has the same thickness as radio-opaque layer 40′.
Suitable processes, such as those described in reference to the embodiment of radio-opaque film 10 shown in
Radio-opaque film 10″ may be manufactured by processes similar to those used to form radio-opaque film 10, with each isolation layer 50 being positioned over and secured to a sublayer 42′, etc. (e.g., by roll calendaring, etc.), then forming each successive sublayer 44′, etc., on an isolation layer 50. After defining the uppermost (or outermost) sublayer 44′, etc., a containment layer 30 is positioned over and secured to that sublayer 44′, etc.
In
For example, in embodiments where the substrate 60 is formed from a paper or a paper-like material (e.g., polyethylene fibers, etc.), it may be readily positioned and repositioned without sticking to a surface (e.g., skin, etc.) over which it is used. A substrate 60 formed from such a material may also impart the radio-opaque film 10′″ with the ability to absorb liquids. Such an embodiment of radio-opaque film 10′″ may be useful as a surgical drape or a similar article to be used in a patient examination room.
In other embodiments, the substrate 60 may be formed from cloth or a cloth-like material (e.g., polyethylene fibers, etc.), which may impart the radio-opaque film 10′″ with a cloth-like appearance, which may be desirable in situations where the radio-opaque film 10′″ is used to form a protective garment, a protective shield (e.g., sheet, etc.), or the like.
As indicated, a radio-opaque film (e.g., radio-opaque film 10, 10′, 10″, 10′″ or any other embodiment of radio-opaque film) of the present invention may be used to protect a patient, a healthcare provider or both from ionizing radiation.
In
The EXAMPLE that follows demonstrates the ability of a radio-opaque film 10 that embodies teachings of the present invention to attenuate ionizing radiation.
Several samples of a radio-opaque film were formed by depositing bismuth oxide onto films of polyethylene terephthalate (PET), such as that marketed under the trade name MYLAR® by E.I. du Pont Nemours & Co. of Wilmington, Del. The PET films were cut to lateral dimensions of 5 cm×5 cm. The bismuth oxide was blended with a PVB binder, with the resulting mixture including 80% bismuth oxide, with the balance comprising PEG binder, glycerine, capric triglyceride, cetyl alcohol and glyceryl sterate. That mixture was then suspended in water to form a slurry with a solids content of about 80% w/w.
Two sets of samples were formed using the PET films and the bismuth oxide slurry. In a first set of the samples, the bismuth oxide slurry was applied to the precut PET films at a controlled thickness of 0.010 inch (0.25 mm), then placing another precut PET film over the bismuth oxide slurry and allowing the water to evaporate from the slurry. A second set of samples were prepared in the same manner, but with application of the bismuth oxide slurry at a controlled thickness of 0.015 inch (0.38 mm).
In addition to the bismuth oxide samples, control samples were prepared. Preparation of the control samples included cutting 5 cm×5 cm swatches from an ESP™ radiation shielding examination glove available from Boston Scientific of Natick, Mass. That radiation shielding glove includes lead particles dispersed throughout an elastomer at a solids content of approximately 60%, by weight.
Once sample and control swatch preparation was complete, three tests were performed. In each test, a dosimeter was placed beneath each sample and control swatch, and exposed to ionizing radiation from a Philips C-Arm mobile x-ray device. In a first test, the samples and control swatches were exposed to x-ray radiation at an intensity of 60 kVp for 60 seconds. In a second test, the samples and control swatches were exposed to x-ray radiation at an intensity of 95 kVp for 60 seconds. In a third test, the samples and control swatches were exposed to x-ray radiation at an intensity of 110 kVp for 60 seconds.
The data provided by both
In a second study, the ability of a radio-opaque film 10 (
Two radio-opaque films 10 were evaluated: a first having a single radio-opaque layer (a 0.75 mm thick bismuth oxide layer); and a second, which included a 0.7 mm thick bi-layer made of two radio-opaque materials: a 0.35 mm thick bismuth oxide layer (80% w/w bismuth oxide, 20% w/w binder (see EXAMPLE 1); and a 0.35 mm thick bismuth-bismuth oxide layer (80% w/w bismuth-bismuth oxide, including 50% w/w bismuth and 50% w/w bismuth oxide, with the balance comprising the binder (see EXAMPLE 1). Both radio-opaque films included two sheets (about 0.1 mm thick) of TYVEK® flashspun polyethylene fibers with a radio-opaque layer therebetween.
The lead foil used in the study was 99.9% pure foil available from Alfa Aesar. The lead shield, which had a thickness of 1.5 mm, was a 0.5 mm lead-equivalent STARLITE radiation shield (Lot# 10166) available from Bar Ray Products of Littlestown, Pa. The lead-free shield, which had a 0.5 mm lead-equivalent thickness of 1.9 mm, was a TRUE LITE radiation shield (Lot# 10467) available from Bar Ray Products. The lead-free shield, which had a thickness of 1.9 mm, was made from elemental antimony (Sb), in the form of particles embedded in an elastomeric material at a weight ratio of about 1:1.
NANODOT® dosimeters, available from Landauer, Inc., of Glendale, Ill., were used to detect the amount of x-ray radiation that passed through each of the tested products.
Two sets of tests were performed. In a first set of tests, the x-ray attenuating ability of the single layer 0.75 mm specimen was evaluated. In a second set of tests, the ability of the two-layer 0.7 mm specimen to attenuate x-ray radiation was evaluated.
In each set of tests, attenuation was evaluated at x-ray energies of 60 kVp, 90 kVp and 120 kVp. Each of the tests was repeated five times, with previously unused dosimeters used in each individual test.
In the first set of tests, five dosimeters were placed on a surface within an anticipated field of exposure having a diameter of about 250 mm. A Tyvek test specimen and a sample of each of three comparative products (i.e., the lead film, the lead shield and the lead-free shield) were placed over four of the dosimeters. Another dosimeter was not covered. A National Institute of Standards and Technology (NIST)- and ISO-calibrated x-ray source available at Landauer's laboratory was used to simultaneously expose each product to x-ray radiation. One of the predetermined x-ray energies was then generated, with the tested product and the comparative products, as well as the bare dosimeter, within the field of exposure. An ion chamber was used to measure the radiation dosage at the beginning of each of the tests (i.e., different energies). Ion chamber counts were obtained three times to verify reproducibility of the measurements. In each test (i.e., for each energy of x-ray radiation), exposure to the x-ray radiation lasted for 60 seconds.
Following each test, the dosimeters were removed and stored carefully to maintain traceability. Data was then obtained from the dosimeters to determine the measured incident dosages of x-ray radiation (the control provided by the bare dosimeters) and the transmitted dosages of x-ray radiation (the amounts of x-ray radiation attenuated by each product, as measured by the covered dosimeters).
From these data, the amount of attenuation by each product was calculated using attenuation by the 0.5 mm lead foil (“Lead Foil”) as a baseline. Specifically, the transmitted mrad values for the other products were divided by the transmitted mrad values for the 0.5 mm lead foil. The percent (%) attenuation was then calculated as the complement of the quotient.
The 0.5 mm lead foil attenuates x-ray radiation better than the other products. In decreasing order of x-ray attenuation ability were the 1.5 mm lead shield (98%), the 1.9 mm lead-free shield (92%) and the much thinner 0.75 mm Tyvek test specimen (about 85%). Of course, by increasing the thickness of the radio-opaque layer of the test product, its ability to attenuate x-ray radiation would also increase, approaching that of the lead foil.
In the second set of tests, the ability of two-layer, 0.7 mm test product (“2L BB” in TABLE 2 below) to attenuate three different energies of x-ray radiation was evaluated. In each of the tests, a dosimeter was placed beneath the test product, while another dosimeter was directly exposed to the x-ray radiation. At each energy, five sets of data were obtained. TABLE 2 tabulates the average dosage, in mrad, at each of the three x-ray radiation energies (kVp).
In
From the foregoing, it is apparent that a radio-opaque film that incorporates teachings of the present invention may provide comparable radiation attenuation to existing radio-opaque materials at a significantly reduced thickness and weight.
Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the invention or of any of the appended claims, but merely as providing information pertinent to some specific embodiments that may fall within the scopes of the invention and the appended claims. Other embodiments of the invention may also be devised which lie within the scopes of the invention and the appended claims. Features from different embodiments may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents. All additions, deletions and modifications to the invention, as disclosed herein, that fall within the meaning and scopes of the claims are to be embraced thereby.
This application is a continuation-in-part of U.S. patent application Ser. No. 12/683,727, filed on Jan. 7, 2010, pending, the disclosure of which is hereby incorporated herein, in its entirety, by this reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12683727 | Jan 2010 | US |
| Child | 12897611 | US |
