Patent Publication Number: US-2004041107-A1

Title: Radiation attenuation system

Description:
FIELD  
       [0001] The present disclosure relates to a radiation attenuation system. More particularly the present disclosure relates to a radiation shield.  
       BACKGROUND  
       [0002] A lead protective barrier or shield to attenuate radiation is generally known. Such shield is typically fabricated from a lead vinyl web loaded with lead. However, such shield has several disadvantages because the shield is of only average pliability, retains permanent creases during normal handling, and is not capable of draping smoothly over regions of a patient to be shrouded. Further such shield is not generally disposable, or is the subject of disposal only at great inconvenience and cost (due to the lead content).  
       [0003] Accordingly, it would be advantageous to provide a radiation attenuation system that is relatively flexible and compliant, and which provides a relatively high degree of comfort to the user. It would further be advantageous to provide a radiation attenuation system that provides attenuation of radiation for health care personnel working in an x-ray environment. It would also be advantageous to provide a radiation attenuation system that is disposable. It would also be advantageous to provide a radiation attenuation system that is sterilizible before use. It would also be advantageous to provide a radiation attenuation system that includes a moisture barrier. It would be desirable to provide for a radiation attenuation system having one or more of these or other advantageous features.  
       SUMMARY  
       [0004] An exemplary embodiment relates to a system for the attenuation of radiation. The system includes a polymeric resin comprising a web. The system also includes a radiation attenuation material dispersed at least partially in the web. The system has a radiation transmission attenuation factor of at least about 10% of a primary 100 kVp x-ray beam.  
       [0005] Another exemplary embodiment relates to a shield for the attenuation of radiation. The shield includes a sheet comprising a plurality of layers. The shield also includes a radiation attenuation material dispersed at least partially in the plurality of layers. The sheet has a radiation transmission attenuation factor of at least about 10% .of a primary 100 kVp x-ray beam.  
       [0006] Another exemplary embodiment relates to a method of making a radiation attenuation system. The system includes a radiation attenuation material dispersed at least partially in a polymeric resin. The method includes extruding the radiation attenuation material and the polymeric resin thereby forming an extrusion. The method also includes forming the extrusion into a web. The web has a radiation transmission attenuation factor of at least about 10% of a primary 100 kVp x-ray beam. 
     
    
    
     DESCRIPTION OF THE FIGURES  
     [0007]FIG. 1 is a perspective view of a radiation attenuation system according to an exemplary embodiment.  
     [0008]FIG. 2 is a cross-sectional view of the system of FIG. 1 along line  2 - 2  of FIG. 1.  
     [0009]FIG. 3 is a sectional view of a radiation attenuation system according to an alternative embodiment.  
     [0010]FIG. 4A is an exploded perspective view of a web according to an exemplary embodiment.  
     [0011]FIG. 4B is a fragmentary perspective view of the web of FIG. 4A showing an effective coverage area.  
     [0012]FIG. 5 is a perspective view of a web according to an alternative embodiment.  
     [0013]FIG. 6 is a schematic view of a shelter according to an exemplary embodiments.  
     [0014]FIG. 7 is a perspective view of a shelter according to another exemplary embodiment.  
     [0015]FIG. 8 is a schematic view of a radiation attenuation system according to another exemplary embodiment.  
     [0016]FIG. 9A is a perspective view of a radiation attenuation system according to another exemplary embodiment.  
     [0017]FIG. 9B is a perspective view of another radiation attenuation system according to another alternative embodiment.  
     [0018]FIG. 10A is a perspective view of a radiation attenuation pad according to an exemplary embodiment.  
     [0019]FIG. 10B is a plan view of a thyroid shield according to an exemplary embodiment.  
     [0020]FIG. 10C is a plan view of male gonadal shield according to an exemplary embodiment.  
     [0021]FIG. 10D is a plan view of a female gonadal shield according to an exemplary embodiment.  
     [0022]FIG. 10E is a plan view of a diaper according to an exemplary embodiment.  
     [0023]FIG. 10F is a perspective view of a wrap around protective apron configured for full torso protection according to an exemplary embodiment.  
     [0024]FIG. 10G is a perspective view of a front shield protective apron configured for full torso protection according to an exemplary embodiment.  
     [0025]FIG. 10H is a side elevation view of a miniapron configured for partial torso protection according to an exemplary embodiment.  
     [0026]FIG. 10I is an anterior view of a female patient shown wearing a breast shield according to an exemplary embodiment.  
     [0027]FIG. 10J is an anterior view of a male patient wearing a scoliosis shield according to an exemplary embodiment.  
     [0028]FIG. 10K is a perspective view of a glove according to an exemplary embodiment.  
     [0029]FIG. 10L is a perspective view of a patient undergoing radiological treatment about the head and neck of the patient, and is shown wearing an eye disc according to an exemplary embodiment.  
     [0030]FIG. 10M is a perspective view of a barrier according to an exemplary embodiment.  
     [0031]FIGS. 10N and 10O are schematic views of a drape showing the drape disposed over a patient in preparation for a cardiac catheterization procedure according to an exemplary embodiment.  
     [0032]FIG. 10P is a perspective view of a radionuclide transportation and/or storage device according to an exemplary embodiment.  
     [0033]FIG. 10Q is a perspective view of a patient undergoing radiation treatment and/or examination and wearing a marker according to an exemplary embodiment.  
     [0034]FIGS. 10R and 10S are of film markers according to an exemplary embodiment.  
     [0035]FIG. 10T is a top plan view of an infant stabilization device incorporating protective radiation shields according to an exemplary embodiment.  
     [0036]FIGS. 10U, 10V and  10 W are schematic views showing a variety of patient positioning devices according to an exemplary embodiment.  
     [0037]FIG. 10X is a perspective view of a fluoroscopy table pad adapted for angiography according to an exemplary embodiment.  
     [0038]FIG. 10Y is a top plan view of a density wedge according to an. exemplary embodiment.  
     [0039]FIG. 12 is a block diagram of a method of making a radiation attenuation system. according to an exemplary embodiment.  
     [0040]FIG. 13 is a schematic view of an apparatus for making a radiation attenuation system according to an exemplary embodiment. 
    
    
     DETAILED DESCRIPTION OF PREFERRED AND OTHER EXEMPLARY EMBODIMENTS  
     [0041]FIG. 1 shows a radiation attenuation system  310   a  providing a radiation drape, pad or shield  312 . Shield  312  may be useful in blocking, attenuating and/or reflecting radiation and assisting in the protection of a worker (e.g. a physician or technologist during a medical procedure) in tasks. Shield  312  may attenuate radiation provided by a variety of natural or man-made sources over a wide range of the electromagnetic spectrum from wavelengths of 1.0×10 −15  meters (e.g. cosmic rays), to 1.0×10 6  meters (e.g. radiation from AC power lines) including visible and invisible light, and may find incidental uses at relatively low or high: frequency extremes (including gamma rays). Shield  312  may also selectively isolate regions for direction of radiation, and may selectively shroud or protect regions beyond the contours or margin of the zone of interest.  
     [0042] Shield  312  may include a radiation attenuation region (shown as a strip  314 ) for the attenuation of radiation. A fenestration area  316  of shield  312  provides access to an area of interest (e.g. patient) through an aperture (shown as a circular hole  318   a  and a parallelogram shaped hole  318   b ) for conducting various invasive procedures, such as the fluoroscopic guidance and/or manipulation of instruments during surgical-procedures. Strip  314  may be at least partially surrounded by a panel (shown as a window  320 ) that is relatively clear or translucent for the viewing of objects (e.g. controls, instruments, etc.) beneath shield  312 . Shield  312 , strip  314 , holes  318   a  and  318   b  and window  320  may be of a variety of shapes and sizes, which may be dictated at least in part by the particular application (e.g. angiography, femoral angiography, general biopsy, pacemaker implant, etc.). Indicia  334  for identification or personalization of shield  312  may be identified or written on shield  312 .  
     [0043]FIG. 2 shows a cross-sectional view of shield  312 . The attenuation of radiation is provided by at least a web  322   a  (e.g. matrix, sheet, film, polymer radiation attenuation material, etc.) of attenuation material or filler, such as barium sulfate powder, bismuth powder, or other attenuating materials/fillers compounded (e.g. mixed, blended, alloyed, etc.) with a polymeric carrier, and a web  322   b . On one side of shield  312 , web  322   a  may be attached to a cover  324  such as a fabric (e.g. soft carded polyester) for placement next to the area of interest (e.g. patient). Cover  324  provides some comfort to a user (e.g. patient) and assists in the, retention of body heat. On another side of shield  312 , an absorbent layer  326  (e.g. polyester) may be coupled to web  322   b  for maintaining fluid control (e.g. block blood from seeping onto the patient during a surgical procedure). Absorbent layer  326  may include fibers (e.g. wet-laid, spunlaced, etc.) bonded or woven to a reinforcing layer  332  network frame or scrim  372 .  
     [0044] Absorbent layer  326  may be attached to a relatively liquid impervious layer  328   a  such as plastic, polyethylene, etc. Impervious layer  328   a  may assist in inhibiting the transmission of fluid from absorbent layer  326  to cover  324  (i.e. separates fluid from the patient). An optional relatively liquid impervious layer,  328   b  may be disposed between web  322   a  and  322   b . A fastener  330  (e.g. adhesive, stitching, spot weld, ultrasonic weld, hot melt, laminate, etc.) may attach the layers of shield  312  (i.e. absorbent layer  326 , impervious layers  328   a  and  328   b , webs  322   a  and  322   b , and cover  324 ) to each other.  
     [0045]FIG. 3 shows a radiation attenuation system  310   b  having a radiation barrier  340 . Barrier  340  includes a layer or web  322   c  including a monolayer (i.e. at least one layer) shown as a primary attenuation layer  322   d  of a relatively flexible material (e.g. polymer resin). Barrier  340  may be charged with a radiation attenuation material such as metal powder (shown as a particle  342   a  and a particle  342   b ). Particle  342   a  is shown generally evenly distributed and dispersed. within layer  322   d.    
     [0046] A secondary attenuation layer  322   e  of web  322   c  is shown attached to layer  322   d  by a fastener (e.g. hot melt adhesion or laminate). Without intending to be limited to any particular theory, it is believed that multiple attenuation layers may increase the radiation attenuation factor of the radiation attenuation system. Two attenuation layers are shown in FIG. 3, and the radiation attenuation system may have multiple attenuation layers (e.g. 3, 6, 20 layers, etc.) according to alternative embodiments.  
     [0047] A tie layer  344  may attach attenuation layer  322   c  to a covering (shown as a skin  346 ). The tie layer may include: polyethylenes such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene, very low density polyethylene (VLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE) and metallocene polyethylene (MPE); ethylene copolymers such as ethylene vinyl acetate (EVA), ethylene methacrylate (EMA); ethylene ethylacrylate (EEA) and ethylene butyl acrylate (EBA); acid copolymers such as ethylene methacrylic acid and ethylene acrylic acid; lonomer including zinc and sodium SURLYN film (which may be made of synthetic thermoplastic resin for use in commercial and industrial wrapping) commercially available from E. I. du Pont de Nemours and Company of Wilmington, Del.; extrudable adhesive polymers such as BYNEL adhesive resins (which may be for industrial use) commercially available from E. I. du Pont de Nemours and Company of Wilmington, Del. (maleic anhydride copolymer); thermoplastic elastomers such as styrenic block copolymer, thermoplastic polyurethanes, polyolefin blends, elastomeric alloys, thermoplastic copolyesters and metallocene plastomer; and polypropylenes, etc.  
     [0048] Skin  346  may function as a partition or wall to separate attenuation layers  322   d  and  322   e  from a user. According to an alternative embodiment, the skin may be made from a material that is the same or different from the material of the attenuation layers, or from a material to enhance processability, softness or comfort for a user. According to another alternative embodiment, the skin may function as a heat-sealing layer. According to other alternative embodiments, the skin may be provided with a colorant (e.g. clear, blue, red, etc.). (The web is typically dark colored, due in part to the color of the attenuation material.). Skin  346  may be attached to a cover layer  348  such as a fabric. One or, more of the layers of barrier  340  may be attached or coupled to each other with a fastener. According to other alternative embodiments, the fastener may be omitted. According to still other alternative embodiments, the cover and the absorbent layer may merely surround the web (e.g. as an envelope)and need not necessarily be attached to the web.  
     [0049]FIG. 3 also shows the radiation attenuation ability of barrier  340 . A primary incident radiation beam  354   a  is shown having partially penetrated barrier  340 . Beam  354   a  interacts with particle  342   a  in primary attenuation layer  322   d , and is absorbed by particle  342   a . Another primary beam is shown having penetrated primary attenuation layer  322   d , interacted with particle  342   b  in secondary attenuation layer  322   e , and absorbed by particle  342   b . A scattered radiation beam  356  is shown having penetrated primary attenuation layer  322   d  and absorbed by particle  342   a . According to alternative embodiments, primary beams and scattered beams of incident radiation may be attenuated by additional multiple attenuation layers of the barrier or within a monolayer barrier.  
     [0050] Multiple layers of radiation attenuation system  310   b  may cause the increase in the thickness of web  322   c , which suitably has a thickness of about 1-300 mil, suitably about 1-50 ml, suitably about 1-10 mil and more suitably about 5-8 mil. (Thus, the total weight of radiation attenuation system may be minimized.) The thickness of the web may also be determined in part by the desired radiation attenuation factor, and the weight and volume requirements of the attenuation material.  
     [0051] As shown in FIGS. 4A and 4B, the attenuation material is suitably distributed generally evenly in each of the attenuation layers of a web  322   f . Particles  342   b  are distributed throughout an intermediate film  346   b  “sandwiched” or surrounded by a cover film  346   a  having particles  342   a , and a base film  346   c  haying particles  342   c . Web  322   f  may also include layers or films  346   d  and  346   e . Particles  342   a ,  342   b ,  342   c ,  342   d  and  342   e  are shown generally evenly dispersed on a dispersion face  350  of each of base film  346   a , intermediate film  346   b , cover film  346   c  and films  346   d  and  346   e . On assembly of films  346   a ,  346   b ,  346   c ,  346   d  and  346   e . (e.g. as a monolayer laminate) particles  342   a ,  342   b ,  342   c ,  342   d  and  342   e  effectively cover the entire surface area of web  322   f  in an effective coverage area  352 , such that substantially all incident radiation will be attenuated by web  322   f  (see FIG. 4B).  
     [0052] The degree of radiation-transmission attenuation factor by the radiation attenuation system will depend in part on the specific application to which the radiation attenuation system is put. For example, for medical applications the radiation attenuation system may have a radiation transmission attenuation factor of a percent (%) greater than about 50%, suitably greater than about 90%, suitably greater than about 95%. For other applications, such as articles of clothing, a radiation transmission attenuation factor of a percent of about 10-50%, suitably 10-20% may be sufficient. Any radiation attenuation system may have radiation transmission attenuation greater than at least about a factor of a percent of about 10%, suitably about 10-98%, suitably greater than about 50% (with reference to a 100 kVp x-ray beam). The radiation attenuation system may also at least partially attenuate gamma rays, and may have a gamma ray attenuation fraction of at least about 10% of a 140 keV gamma radiation source.  
     [0053] The material of the web is generally light and flexible, to in maximize workability for processing, bending, folding, rolling, shipping, etc. The web may be formable (e.g. deformable) or compliant, and relatively “stretchable” (e.g. elastic). The shape of the web may be determined in part by the material to which the web is bound. For example, the shape of the web could be relatively planar if bound to a wall, and the shape of the web could be generally curved if bound to a corrugated material. While the resin of the web may partially attenuate some radiation, greater quantities of flexible material in the web may increase flexibility and comfort, and decrease the likelihood of cracking. According to alternative embodiments, the web may be generally rigid and inflexible.  
     [0054] Suitable materials for the web include: polyethylenes such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density, polyethylene, very low density polyethylene (VLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE) and metallocene polyethylene (MPE); ethylene copolymers such as ethylene vinyl acetate (EVA), ethylene methacrylate (EMA), ethylene ethylacrylate (EEA) and ethylene butyl acrylate (EBA); acid copolymers such as ethylene methacrylic acid and ethylene acrylic acid; Ionomer including zinc and sodium SURLYN film (which may be made of synthetic thermoplastic resin) for use in commercial and industrial wrapping commercially available from E. I. du Pont de Nemours and Company of Wilmington, Del.; extrudable adhesive polymers such as BYNEL adhesive resins which may be for industrial use) commercially available from E. I. du Pont de Nemours and Company of Wilmington, Del. (maleic anhydride copolymer); thermoplastic elastomers such as styrenic block, copolymer, thermoplastic polyurethane, polyolefin blends, elastomeric alloys, thermoplastic copolyesters and metallocene plastomer; thermoplastic polyamide (nylon); and polypropylenes, etc. The web may also include synthetic materials such as polyolefins (such as, polypropylene and polybutene), polyesters (such as polyethylene, polyurethane terephthalate and, polybutylene terephthalate), polyamides (such as nylon 6 and nylon 66), acrylonitriles, vinyl polymers and vinylidene polymers (such as polyvinyl chloride and polyvinylidene chloride), and modified polymers, alloys; and semi-synthetic materials such as acetate and polytetrafluoroethylene (PTE) fibers. The web may also include a thermoplastic elastomer (e.g. EPM, EPDM, styrene butadiene styrene or SBS, etc.) and others polymer.  
     [0055] The attenuation material in the web may assist in the attenuation of incident radiation. The amount of attenuation material may depend in part on the degree of flexibility desired in the web, and the degree of attenuation desired. According to a suitable embodiment, the weight of the attenuation material is greater than the weight of the polymeric resin (e.g. weight ratio), suitably by a ratio of about 10:1, suitably by a ratio of about 5:1, suitably by a ratio of about 2:1, suitably by a ratio of about 1:1. According to another suitable embodiment, the volume of the attenuation material may be less than the volume of the polymeric resin (e.g. volume ratio), suitably by a ratio of about 1:1, suitably by a ratio of about 1:3, suitably by a ratio of about 1:5. According to another suitable embodiment, the volume of the attenuation material may be greater than the volume of the polymeric resin, suitably by a ratio of at least about 10:1  
     [0056] Particularly suitable radiation attenuation materials include barium and bismuth powders, and corresponding salts and oxides (e.g. BaSO 4 ). Other suitable attenuation materials include elements having an atomic number greater than about fifty (50) on the periodic table. Other suitable attenuation materials include barium, bismuth, iodine, tin, tungsten, uranium, zirconium and lead, their corresponding salts or oxides, and combinations thereof. According to a particularly suitable embodiment, the radiation attenuation material does not necessarily contain a significant amount of lead (e.g. essentially free of lead).  
     [0057] The size of the radiation attenuation material may in part affect its dispersion within the resin (i.e. relatively larger particles have relatively good dispersion). According to a suitable embodiment, the particles of the attenuation material have a diameter between about 840-10 micron meters (about −20 mesh to −1250 mesh), suitably between about 297-20 micron meters (about −50 mesh to −625 mesh), suitably between about 149-37 micron meters (about −50 mesh to −400 mesh), suitably between about 74-44 micron meters (about −200 mesh to −325 mesh). According to a particularly preferred embodiment, the barium powder is SPARWITE W-10HB high brightness barium sulfate commercially available from Mountain Minerals Co. Ltd. of Calgary, Alberta, Canada having a median particle diameter of about 1.9-2.1 microns. According to a, particularly preferred embodiment, the bismuth powder is commercially available from ASARCO, Incorporated of New York, N.Y.  
     [0058] Referring to FIG. 5, a web  322   g  may be a “fabric” made from fibers  332  attached (e.g. by hydroentanglement or air laying) to a reinforcing network shown as a scrim  372  having horizontal members  374  interconnected with vertical members  376 . The attenuation material may be impregnated in the fiber by a variety of techniques such as fiber spinning process. In the fiber spinning process, a pre-compounded blend is first prepared with relatively fine attenuation powder dispersed within the polymeric matrix (e.g., through a twin screw extrusion). The pre-compounded blend is than fed into an extruder for melt extrusion. The extrudates from the extruder may go through a filter and a “spinneret” to form the fiber.  
     [0059] The web of the radiation attenuation system, which includes a flexible resin and an attenuation material, may be used in a variety of applications. As shown in FIG. 6, radiation attenuation system  310   a  may be incorporated into the components of a relatively permanent shelter (shown as a housing unit  382 ). Housing unit  382  may be useful in situations of generally, continuous radiation exposure, and where users would need to stay for long periods. System  310   a  is shown in a roof  384  to attenuate ambient radiation or radiation from the atmosphere. System  310   a  may be incorporated into an architectural or construction structure or article such as a wall panel or board  386  or a floor  388 . System  310   a  may be incorporated into an article of furniture such as a partition wall, which may be collapsible (e.g. accordion style folding), or floor covering (shown as a carpet  390 ) above a basement  380 . According to an alternative embodiment, the radiation attenuation system may also be combined with a construction element, such as a concrete floor or wall, a wood board or panel, etc. to “line” the construction elements of the building. According to another alternative embodiment, the radiation attenuation system may be used in the insulation of buildings (e.g. to attenuate radon “gas”).  
     [0060] As shown in FIG. 7, radiation attenuation system  310   a  may be incorporated into the components of a relatively temporary shelter (shown as a tent  400 ). Tent  400  may be useful in situations of generally temporary radiation exposure such as an area where there has been an atomic or nuclear explosion or accident. Wall  402  and floor  404  of tent  400 , may be lined with system  310   a  to substantially shield the occupant from radiation. According to an alternative embodiment, the radiation attenuation system ray be attached to a more permanent shelter such as a temporary building, housing unit or work environment.  
     [0061] As shown in FIG. 8, radiation attenuation system  310   a  may be incorporated into a garment or article of clothing. The article of clothing may be useful in situations of generally temporary radiation exposure such as an area where there has been an atomic or nuclear explosion or accident, health care areas, etc. The article of clothing could extend the work time of the user in an area, and provide a relatively suitable level of protection against radiation. The article of clothing could also be useful by space travelers working in space exploration to attenuate electromagnetic radiation from, outer space. This could be in the form of radiation protection clothing or other radiation protection system forms. As shown in FIG. 8, the article of clothing (shown as a suit  420 ) includes a head cover  422 . (e.g. hood, hat, mask, eye protector, glasses, goggles, etc.), a body cover  426  (e.g. coat, jacket, tunic, shirt), a leg cover  428  (e.g. leggings, pants, coveralls, bibs, etc.), a foot cover  430  (e.g. shoes, shoe cover, boot, etc.) and a hand cover  432  (e.g. gloves, mittens, etc.) each incorporating radiation attenuation system  310   a.    
     [0062] As shown in FIG. 9A, radiation attenuation system  310   a  may be incorporated in a sheet of material (shown as a blanket  410 ). Blanket  410  is shown wrapped around a storage container or water cooler  412  (e.g. in, a work environment such as a nuclear reactor plant or atomic/nuclear waste management sites) to attenuate relatively low level radiation. According to an alternative embodiment, the blanket could be used as a “space blanket” to cover areas emitting radiation at relatively low levels. According to other alternative embodiments, the blanket could be used as a part of the walls or wall partitions that typically protect workers who are outside a workspace (e.g. medical cath lab, special procedures lab, etc.). According to other alternative embodiments, the blanket could be used to cover equipment or personnel during space travel and to attenuate electromagnetic radiation from outer space.  
     [0063] According to an alternative embodiment, the blanket may be a full drape, so that a worker (e.g. physician or technologist) could relatively quickly and easily roll out the drape and the radiation protection would already be in place (i.e. web could be a part of the entire drape). According to other alternative embodiments, the radiation attenuation system (i.e. web of radiation attenuation material) may be incorporated in a drape of the following types angiography femoral angiography, pain management, general or specialized biopsy, TIPS/IJ, dialysis shunt implant, pacemaker implant, radium implant, vascular surgery, etc. According to an alternative embodiment, a femoral angiography shield may have a length greater than its width (e.g. corresponding to a leg), and may include a relatively long, aperture for access to the area of interest (erg. femoral artery). According to still, other alternative embodiments, the radiation attenuation system or the web may replace the plastic or fluid impervious layer in conventional drapes such as model No. 44207-0 or 48433-0 “Universal” angiography drapes commercially from Deka Medical, Inc. of Tyler, Tex.  
     [0064] As shown in FIG. 9B, radiation attenuation system  310   a  may be incorporated into a generally rigid container  440 . Container  440  may be useful for housing and attenuating radiation from relatively high energy radiopharmaceuticals (e.g. radioactive seeds or implants) that may be used in nuclear medicine procedures (e.g. treatment of brain tumors). Container  440  includes a circular wall  442  (which may be threaded) between a removable cover or cap  444  and a fixed base  446 .  
     [0065] The radiation attenuation system may be used in medical applications by physicians and other healthcare workers (e.g. interventional cardiologists and radiologists, pain management physicians, radiation therapy/oncologists, electophysiologists, etc.) who may work with fluoroscopy or in nuclear medicine. The radiation attenuation system (i.e. the web of having the attenuation material) may be configured and incorporated in any number of convenient shapes and sizes such as: radiation protection pads, thyroid shields, male gonadal shields, female gonadal shields, diapers aprons (including miniaprons) breast shields, scoliosis shields, gloves, eye disks, barriers, and infant stabilization/shield members, shields, markers, table pads and density wedges. Such articles may be relatively easily trimmed to shape or fit to the extent necessary or desirable. Exemplary articles of the radiation attenuation shield are shown in FIGS.  10 A through FIG. 10Y.  
     [0066]FIG. 10A shows a radiation pad  10 . Pad  10  is comprised of a panel  12  shown in the form of a rectilinear slab. Pads such as the radiation pad  10  are typically placed over an area of a user (e.g. patient) to be examined with a central cut or tapered aperture  14  defining the region within which the worker (e.g. examiner) will be working on the user. Aperture  14  may be placed coincident with the primary x-ray beam. The tapering presents a convenient field within which to work and to provide an-edge, which will reside closely in contact with the body of the user. The radiation attenuating material from which the web is intended to at least partially attenuate radiation near the worker (e.g. physician) as he works on a patient. Such shields assist in the protection of the hands, arms, face and eyes of the worker when working close to a primary x-ray beam, preventing such debilitating or unwanted effects as the development of radiation-induced arthritis, dermatitis or hair loss. This can be a consideration whether the radiation is associated with a mammography, having a primary beam less than about 20 kVp as is for relatively, high energy, and relatively high resolution work with beams over about 120 kVp. Further, in some nuclear medicine applications, medical workers may require a radiation attenuation system that can attenuate gamma rays and radiation levels of at least about 140 keV. Shields can be tailored for use throughout this energy range and are conveniently adaptable for use beyond it.  
     [0067]FIG. 10B shows a thyroid shield  20 . Shield  20  may be comprised of a body of radiation attenuating material  22  bearing a cloth or other type of covering  24  to improve comfort. The thyroid shield includes opposed ends  26 , which provide an attachment member, such as that known as Velcro, to facilitate attachment of the thyroid shield to a user (e.g. patient).  
     [0068]FIGS. 10C and 10D illustrate male and female gonadal shields  30  and  40  (respectively). These shields are configured to protect the gonadal region of a user (e.g. patient) during a radiological procedure.  
     [0069]FIG. 10E is a view of a diaper  50  having a fastener  52  and  54  at opposed upper edges to facilitate the disposition of such a diaper about a user (e.g. patient). Diaper  50  may be made in a range of sizes to fit adult or adolescent patients as well as infants, to protect the gonadal and abdominal regions of the patient during a radiological procedure.  
     [0070]FIGS. 10F and 10G show full torso protective aprons designated  60  and  62 , respectively. Torso apron  60  is comprised of an enveloping shroud or apron  64  that encircles the front and back of the body of the wearer. Opposed marginal edges meet at a juncture  65 , which is secured by fasteners  66 . If desired, the body of apron  60  may be covered with a cloth, cloth-like material, or other types of material to improve wearer comfort and to place and secure fasteners  66 . Body panel  67  of apron  62  drapes only the frontal portion of the wearer. In this instance, apron  62  does not surround the torso. It is secured to the wearer by ties or straps  68  encircling the waist region.  
     [0071] A miniapron  70  is shown in FIG. 10H. Miniapron  70  is comprised of a body or panel region  72  suspended from the waist of a wearer by ties or a fastening member  74 . Miniapron  70  covers only a portion of the lower torso of the wearer. The apron designs of FIGS. 10F and 10G and  10 H are configured to provide both examiner patient comfort and examiner/patient safety in connection with radiological procedures or other exposure to sources of radiation.  
     [0072]FIG. 10I shows a breast protective barrier drape or shield  80  worn by a user (e.g. female patient), for example during a mammographic x-ray procedure. Breast shield  80  is thus comprised of an upper shield  82  which protects the portion of the anatomy of the user that is not subjected to examination, and shield  82  extends downwardly from the body of the user (e.g. from the shoulder toward the abdomen). A further, shielding element  84   is  provided about the gonadal region of the user (e.g. patient) to protect-those organs as well. Accordingly, only the area to be examined is presented for irradiation while surrounding regions are protected against unwanted exposure.  
     [0073]FIG. 10J shows a scoliosis shield  90 . Shield  90  drapes from the shoulder region of the user (e.g. patient) to the lower abdomen. Shield  90  further includes a gonadal shield  92 . The scoliosis shield leaves an exposed region  94  for examination.  
     [0074]FIG. 10K shows a protective glove designated generally as  100  fabricated from radiation shielding material. Glove  100  may be used by a health care practitioner when manipulating instruments or tools proximate a primary beam or in a region of secondary or scattered radiation; it may be worn by a user (e.g. patient) to protect his or her hand, during examination of the body of the user in regions next to such a radiation source; or the glove may be worn by an individual who is required to handle sources of radioactive material.  
     [0075]FIG. 10L shows a perspective view of a user (e.g. patient) wearing a protective eye disc  110 . The user is shown supported on an examination table  112  above a photographic plate  114 , positioned for irradiation by an x-ray tube  116  to provide an x-ray image of the head and/or neck region of the user. In this instance, the eye protection assists in safeguarding the optical anatomy of the user from unwanted or undesirable exposure to the primary beam. The shield may also be useful in “tanning rooms.” 
     [0076]FIG. 10M shows protective barriers and shields  120  and  122  used to protect personnel in an x-ray examination room or the like. In this instance, barrier  120  is associated with an examination table  123  placed beneath the tube of an x-ray machine  124 . When a user (e.g. patient) is examined on table  123 , drape or shield  120  confines scattered radiation from beneath the table. Also, during fluoroscopic procedures with the x-ray tube underneath the table, the drape or shield  120  could confine the scattered radiation underneath the table and attenuate radiation to at least partially protect the examining attendant and patient. Shield  120  may envelop the entirety of examination table  123  or be placed only on the side or sides toward which the examining attendant faces. This may be in a form similar to a “table skirt” that extends to the floor. Barrier  122  protects that attendant, as also shown in FIG. 10M, as well. In this case, the shield is formed with a cut-out or visually transparent component  125  through which the worker (e.g. examiner) may observe the patient. A certain amount of radiation may be transmitted through region  125 .  
     [0077] Barriers of the sort shown in FIG. 10M can be of assistance in establishing either remote or temporary x-ray facilities. Most x-ray rooms include lead lining in or on the walls to confine radiation and prevent stray radiation from leaving the region of the x-ray apparatus. It is not always convenient or desirable to provide that type of lead-circumscribed environment, in which case protective barriers are capable of providing temporary but nonetheless relatively efficient shielding. Barriers of the sort shown in FIG. 10M, but modified appropriately, may also be useful in space travel to line the walls of a space vehicle or space station to attenuate electromagnetic radiation from outer space.  
     [0078]FIGS. 10N and 10O show a protective drape, in this instance configured for a cardiac catheterization procedure to be performed on a user (e g. patient). A protective drape  130 , is sized to cover the user essentially over the majority of the body, being draped from the upper chest region to the lower legs as best viewed in FIG. 10N. Drape  130  could be of sufficient width to span entirely across the user (e.g. patient) and the operating table. Drape  130  is fabricated from radiation shield. A first keyway or cut-out  132  is formed in the upper thigh region while a panel or window  134  of-neutral material is provided in the drape, in the region of the heart of the user. The cut-out provides the worker (e.g. physician) with an entry point to insert a needle or through which to introduce the catheter instrumentation. The patient is subjected to x-ray radiation passing through the region of window  134 . Watching an appropriate display responsive to that radiation, the worker may manipulate the catheter from the region of cut-out  132  into proper position proximate the heart. During that procedure, however, protective drape  130  at least partially protects operating room personnel from scattered radiation.  
     [0079] The compliant nature of drape  130  allows it to reside closely next to the body of the patient. It is comfortable and fits positively against the undulating surface of the patient, thus improving its stability while the surgical team is operating on the body of the patient. The coefficient of friction between the drape and the skin of the patient adds to that stability, preventing movement of the drape during the surgical procedure and further obviating the need to take extraordinary measures to prevent slippage or movement of the drape.  
     [0080]FIG. 10P shows a radionuclide transportation and storage article or device  150 . In this instance, device  150  is comprised of a body of radiation attenuating material having a plurality of blind apertures  154  formed therein. Each of the apertures  154  is dimensioned to receive a vial of radioactive material to be transported and/or stored (e.g. material used in radiation treatment in a hospital). Each of blind apertures  154  may be slightly undersized to ensure a close interference fit between body  152  and the vials to be inserted in those apertures. Once in place, a cover of similar material may be disposed over device  150  and secured in any convenient manner for transport and/or storage.  
     [0081]FIG. 10Q shows a marker  160  placed on a user (e.g. patient) undergoing radiological examination. Marker  160  is positioned at a specific location on the body of the patient to provide a benchmark for measurement on the image resulting from the x-ray procedure. Thus, being radiopaque, a mark will appear either on an x-ray film or on a real time display permitting; a worker (e.g. physician) to measure with reasonable precision the location of internal, anatomy from that known point as evidenced by the marker.,  
     [0082]FIGS. 10R and 10S show film markers such as have been used in the past to identify x-ray films. In each case, a marker  170  is comprised of a support  172  bearing a letter indicia  174  either as an “R”, or as an “L.” These indicia are meant to identify radiographic representations as either the right or left part or extremity of some anatomical element or, if the object being examined is not a patient but an inanimate object, other markers of similar variety may be used to identify specific locations or characteristics. Typically, the support will be radio-transmissive whereas the indicia will be radiopaque. Where such markers are utilized with patients in x-ray examination and especially where the marker is placed in contact with the patient, the marker may then be disposed.  
     [0083]FIG. 10T shows an infant stabilization device including a protective radiological shield  180 . Shield  180  includes a frame  182  having a plurality of straps  184  (or the like) for restraining the infant in position on the stabilization member. A border  186  of radiation attenuating material is disposed peripherally about the stabilization member while the infant may be provided with a diaper  187  likewise made from radiation attenuating material in accordance with the present invention. A cut-out region  188  is provided to allow x-ray examination of the infant or a selected portion of his anatomy. Typically, the infant is placed on the pad and is strapped into position with his hands suitably secured. With shielding in place, a holder such as the parent of the infant (also suitably protected) may assist in the x-ray procedure as required.  
     [0084]FIGS. 10U, 10V and  10 W show different forms of patient positioning devices used in radiological procedures, either investigative or therapeutic. In FIG. 10U, the hand of a patient is positioned on a positioning device  190 ; in FIG. 10V, the leg of the patient is confined within a positioning device  192 ; and in FIG. 10W, the head of the patient is suitably positioned within a device  194 .  
     [0085]FIG. 10X shows a fluoroscopic table pad  200 . Table pad  200  is of a generally rectilinear configuration, shaped as a web  202  fabricated from a one-quarter inch to, one-half inch slab of radiation attenuating material in accordance with the present invention. Zones of neutral material  204  are formed in the pad  200 , here disposed in shape and size as required for angiography. Cut-outs  206  in the pad allow items to be inserted through the pad as may be required. The pad is placed on the table beneath a patient undergoing angiography, during which he is subjected to x-ray radiation from beneath the table. The primary beam is allowed to pass through the pad only in the regions of the neutral material  204 .  
     [0086]FIG. 10Y shows a pair of density wedges  210 . Each of wedges  210  is tapered and thus provides higher density radiopacity at the thicker edge than at the thinner or tapered edge.  
     [0087] According to alternative embodiments; the radiation attenuation system may ,be used in space travel or shelter (e.g. space station or vehicle) applications. Specifically, the system may substantially protect humans or sensitive cargo from radiation that could be present in outer space. According to other alternative embodiments, the radiation attenuation system may have applications in the medical, industrial, clothing, architectural (e.g. furnishings and wall coverings), packaging and shipping: containers (e.g. food, electronics, etc.), construction materials, geotextiles, and vehicular (automotive, boating, airplane, exterior and interior) industries.  
     [0088] According to a preferred embodiment, the radiation attenuation system is generally disposable in whole or in part, thereby minimizing ancillary sources of contamination that may arise from multiple uses. According to another suitable embodiment, the radiation attenuation system is generally non-toxic, recyclable, and/or biodegradable. According to an alternative embodiment, the radiation attenuation system may be reusable (e.g. for attenuation of radiation from atomic/nuclear disaster, clean up, rescue operations, etc.). According to a preferred embodiment, the radiation attenuation system may be sterilized between uses to minimize the likelihood of bacteriological or virus contamination. Sterilization may be performed in any convenient manner, including gas sterilization and irradiation sterilization.  
     [0089] The “durometer” is a suitable measure of the drape and hand, of the radiation attenuation system. For certain applications such as a medical drape, the durometer of the system is suitably less than about 100 Shore “00,” suitably about 5-80, Shore “00”, suitably about 15-40 Shore “00.” Shore “00” may be measured on a Shore durometer commercially available from Shore Manufacturing Company of Jamaica, N.Y. The selection of materials for the radiation system that yield an appropriate softness (which manifests itself in terms of hand and drape viewed in the apparel context) provides a material that is relatively conformable to the body (e.g. patient)or article shrouded.  
     [0090] The “coefficient of sliding friction” (determined as the tangent of the angle of inclination to induce sliding) relative to the body (e.g. patient) or article shrouded is a suitable measure of the friction provided by the radiation attenuation system. The coefficient of friction between the system and the skin of the user (e.g. patient) may add stability, thereby preventing movement of the system during use (e.g. the surgical procedure) and further obviating the need to take extraordinary measures to prevent slippage or movement of the system.  
     [0091] The coefficient of sliding friction of the radiation attenuation system is suitably sufficient to maximize the placement stability of the system when in use, and is sufficiently great enough so that the system cannot be easily dislodged or moved after placement for certain applications. For other certain applications such as a medical drape, the coefficient of sliding friction of the system is suitably at least about 0.15, suitably at least about 0.5, suitably at least about 0.75,suitably at least about 1.0. For specific applications such as a surgical drape or protective shield for direct contact with a user (e.g. patient), the coefficient of sliding friction of the system is suitably at least about 2.0.  
     [0092]FIG. 12 shows exemplary process steps for making the radiation attenuation system according to a three layer coextrusion blown film polymer process method. (According to an exemplary, embodiment as shown in FIG. 13, three extruders may be used to manufacture an “ABA” or three layer structure, with each “A” layer being a skin layer and the “B” or intermediate layer being a radiation attenuation layer.) FIG. 13 shows an apparatus  464  for manufacturing an exemplary radiation attenuation system.  
     [0093] Referring to FIGS. 12 and 13, the radiation attenuation material (i.e. powder) is mixed (step  448 ) in a blender or mixer  466 , and then compounded (step  450 ) in a compounder  468  (such as a twin screw extruder) and then “pelletized” or cut into attenuation pieces or pellets  470  (step  452 ). Pellets  470  are fed into a hopper  498  and melted (step  454 ) e.g. in a melt process. The resulting melt may be pumped or extruded (step  456 ) from an extruder (shown as extruders  472   a ,  472   b  and  472   c ) through a forming die  482 . The resulting extrusion is formed (e.g. “blown,” inflated or filled with air) (step  460 ) to produce an extrusion or “bubble”  484 . Each of the extrusions from each of extruders  472   a ,  472   b  and  472   c  can provide a layer of material to bubble  484 . (Three layers of bubble  484  are shown in FIG. 13. According to an alternative embodiment, one or more layers may be formed according to the number of layers desired in the bubble.) An air ring  480  may blow cooled or chilled air to cool and stabilize bubble  484  (step  460 ). As shown in FIG. 13, an air valve  478  may manipulate the air. According to alternative embodiments, the bubble may be of a variety of shapes such as a film, sheet, bottle, etc. depending on-the application.  
     [0094] Bubble  484  may be pulled by a nip  488 , and collapsed by a wall or frame  486  to form a sheet of a relatively flat web  496  (step  462 ). Web  496  may travel through a set of nips and a number idler rolls  490 . According to alternative embodiments, the web may be further processed (e.g. lamination, die cut, finishing, etc.) depending on the application. According to another alternative embodiment as shown in FIG. 13, web  496  may be corona treated by a corona device  492  depending on the final application. Web  496  may be wound in a roll  494  for storage or shipping.  
     [0095] According to alternative embodiments, the radiation attenuation system may be made according to a variety of polymer process methods, including but not limit to, cast film/sheet process, tubular blown film process, cast sheeting process, sheet calendaring, fiber spinning, blow-molding, injection molding, rotational molding, foam process and compression, transfer molding, profile extrusion and coextrusion, non-woven process, etc.  
     [0096] The radiation attenuation percent (%) of an incident direct radiation beam by a radiation attenuation system was measured. For EXAMPLES 1-3, the results were obtained with a Keithley 35050A Dosimeter with a 15 cc chamber commercially, available from Keithley instruments, Inc. Radiation Measurements Division of Solon, Ohio.  
     EXAMPLE 1  
     [0097] A radiation attenuation sample was prepared. The sample included a radiation attenuation material, of bismuth oxide powder commercially available from ASARCO Incorporated of New York, N.Y. and barium sulfate powder commercially available from Mountain Minerals Co. Ltd of Calgary, Alberta, Canada and having a weight ratio of 22:78. The resin was a model no. PE 1031 low density polyethylene resin (commercially available from Huntsman Corporation of Salt Lake City, Utah) having a density of 0.924 gram per cubic centimeter and a melt index of 0.8 gram per 10 minutes. The weight of the radiation attenuation material to resin polymer material was about 2.3:1. The volume of the radiation attenuation material to resin polymer material was about 1:4.  
     [0098] The sample was die cut into three pieces resulting in Samples, 1, 2 and 3. Sample 1 was one layer of the die cut sample. Sample 2 was two layers of the die cut sample (one piece on top of the other). Sample 3 was three layers of the die cut sample (each piece on top of the other). The radiation, attenuation percent of the Samples are shown in TABLE 1.  
                               TABLE 1                                      70 kVp; HVL = 2.63 mm Al   90 kVp; HVL = 3.41 mm Al   110 kVp; HVL = 4.31 mm Al                                                         Pb       Pb       Pb           Thickness   Attenuation   equivalent   Attenuation   equivalent   Attenuation   equivalent       Sample   (mm)   (%)   (in mm)   (%)   (in mm)   (%)   (in mm)                                                     1   &lt;0.1   8.86   0.001   7.35   0.002   6.52   0.0025       2   &lt;0.1   16.20   0.002   13.68   0.003   11.97   0.0040       3   0.1   21.39   0.0035   18.10   0.005   16.02   0.005                  
 
     EXAMPLE 2  
     [0099] A radiation attenuation sample was prepared. The sample, included a radiation attenuation material of bismuth powder commercially available from ASARCO Incorporated, of New York, N.Y., and barium sulfate powder commercially available from Mountain Minerals Co. Ltd. of Calgary, Alberta, Canada and having a weight ratio of 22:78. The resin was a model no. PE 1031 low density polyethylene resin (commercially available from Huntsman Corporation of Salt Lake City, Utah) having a density of 0.924 gram per cubic centimeter and a melt index 6of 0.8 gram per 10 minutes. The weight of the radiation attenuation material to resin polymer material was about 1:1. The volume of the radiation attenuation material to resin polymer material was, about 1:9.  
     [0100] The sample was die cut into three pieces resulting in Samples 1, 2 an 3. Sample 1 was one layer of the die cut sample. Sample 2 was two layers of the die cut sample (one piece on top of the other). Sample 3 was three layers of the die cut sample (each piece on top of the other). The radiation attenuation percent of the Samples are shown in TABLE 2. At 90 kVp, Sample 1 had ,about a 10% attenuation factor, and Samples 2 and 3 had about a 20% and 30% attenuation factor (respectively). With the loading of attenuation materials in the samples, the effect was about 10% radiation blocking per layer of material. Higher levels of attenuation may be achieved as the compounding material loading is changed, and multiple layers of material are used.  
                               TABLE 2                                      70 kVp; HVL = 2.63 mm Al   90 kVp; HVL = 3.41 mm Al   110 kVp; HVL = 4.31 mm Al                                                         Pb       Pb       Pb           Thickness   Attenuation   equivalent   Attenuation   equivalent   Attenuation   equivalent       Sample   (mm)   (%)   (in mm)   (%)   (in mm)   (%)   (in mm)                                                     1   &lt;0.1   11.93   0.001   10.59   0.003   9.61   0.003       2   &lt;0.1   22.46   0.004   20.24   0.007   18.43   0.007       3   0.1   32.99   0.008   29.72   0.012   27.08   0.013                  
 
     EXAMPLE 3  
     [0101] A radiation attenuation sample was prepared. The sample included a radiation attenuation material of bismuth powder commercially available from ASARCO Incorporated of N.Y., N.Y. and barium sulfate powder commercially available from Mountain Minerals Co. Ltd. of Calgary, Alberta, Canada and having a weight ratio of 22:78. The resin was a model no. PE 1031 low density polyethylene resin (commercially available from Huntsman Corporation of Salt Lake City, Utah) having a density of 0.924 gram per cubic centimeter and a melt index of 0.8 gram per 10 minutes. The weight of the radiation attenuation material to resin polymer material was about 2.3:1. The volume of the radiation attenuation material to resin polymer material was about 1:4.  
     [0102] The sample was die cut into four pieces resulting in Samples 1, 2, 3 and 4. Sample 1 was one layer of the die cut sample. Sample 2 was two layers of the die cut sample (one piece on top of the other). Sample 3 was three layers of the die cut sample (each piece on top of the other). Sample 4 was four, layers of the die cut sample (each piece on top of the other). The radiation attenuation percent of the Samples are, shown in TABLE 3.  
                               TABLE 3                                      70 kVp; HVL = 2.63 mm Al   90 kVp; HVL = 3.41 mm Al   110 kVp; HVL = 4.31 mm Al                                                         Pb       Pb       Pb           Thickness   Attenuation   equivalent   Attenuation   equivalent   Attenuation   equivalent       Sample   (mm)   (%)   (in mm)   (%)   (in mm)   (%)   (in mm)                                                     1   &lt;0.1   11.69   0.003   10.73   0.002   9.94   0.003       2   &lt;0.1   28.00   0.007   25.43   0.010   23.38   0.012       3   0.1   47.93   0.017   43.83   0.025   40.38   0.027       4   &lt;0.2   58.45   0.030   53.55   0.037   49.63   0.040                  
 
     [0103] The radiation system may at least partially “shield” or attenuate radiation from, a gamma radiation source (e.g. gamma-ray). A gamma ray is believed to be made up of photons or small bits of light traveling as waves of energy. Gamma-rays are an example of relatively high energy photons, and are part of the electromagnetic spectrum. The energy carried by photons is typically measured in units of electron volts (eV). For example, visible light is made up of photons with energies of about 2 or 3 ev, and gamma-rays are photons of light with energies of 50,000 eV (50 keV) to 1,000,000,000,000 eV (1 TeV) or higher.  
     [0104] One measure of the shielding of gamma radiation is the attenuation coefficient of a material. The attenuation coefficient shows the ability of the material to “shield” or attenuate gamma rays of a particular energy. The attenuation coefficient may include the measure of the slope of the natural logarithm of the intensity of the gamma radiation plotted against the thickness of the material. Shielding may occur when incident radiation is either reflected or absorbed by a material. Linear density and composition of a material also may affect its ability to shield gamma radiation. The energy of the gamma ray may affect the amount and the means by which it is shielded. Relatively lower energy gamma rays are believed to undergo the photoelectric effect or Compton scattering, while higher energy photons are believed to collide with atoms to produce electron-positron pairs. Density (or ration of attenuation material to the carrier of the attenuation material) is also related to shielding ability.  
     [0105] The radiation attenuation fraction of a relatively high energy radiation beam by a radiation attenuation system may be measured as shown in prophetic EXAMPLE 4.  
     EXAMPLE 4  
     [0106] A radiation attenuation sample may be prepare prepared. The sample may include a radiation attenuation material of bismuth powder commercially available from ASARCO Incorporated of New York, N.Y. compounded in a polymer resin. The weight of the radiation attenuation material to polymer resin may be varied for each sample. Each sample may be tested against both Technetium—99 (with energy level of 140 keV) and Iodine—131 (with energy level of 365 keV) which emits gamma radiation. The attenuation fraction of each sample is shown in TABLE 4.  
                               TABLE 4                                   Technetium - 99 m   Iodine - 131               Weight Ratio   (140 keV)   (365 key)           Thickness   (bismuth:   Attenuation   Attenuation       Sample   (mil)   resin)   Fraction (Tc99m)   Fraction (I131)                  1   &lt;300   1.83:1   .86   .41       2   &lt;300   1.73:1   .73   .32       3   &lt;300   1.17:1   .66   .29       4   &lt;300     1:1   .49   .25                  
 
     [0107] The construction and arrangement of the elements of the radiation attenuation system as shown in the preferred and other exemplary embodiments is illustrative only. Although only a few embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g. variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, the attenuation material may be embedded in the web. The radiation attenuation system may be of a variety of sizes (e g. 125″×75″, 32″×34″, 32″×110″, etc.;). The web may be a relatively fluid impervious layer.  
     [0108] Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present inventions as expressed in the appended claims.