EP1941516A2 - Radio-opaque coatings used as shielding for radiation sources - Google Patents

Abstract

Radio-opaque coatings used to help shield radiation sources in a manner that allows directed radiation to be emitted toward a target while helping to contain off-focus radiation.

Description

Radio-Opaque Coatings Used as Shielding for Radiation Sources

CROSS-REFERENCE TO RELATED APPLICATION The present non-provisional Application claims the benefit of commonly owned provisional Application having serial number 60/714,817, filed on September 6, 2005, and entitled RADIO-OPAQUE COATINGS USED AS SHIELDING FOR RADIATION SOURCES, which Application is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to radio-opaque coatings used to help shield radiation sources in a manner that allows directed radiation to be emitted toward a target while helping to contain off-focus radiation.

BACKGROUND OF THE INVENTION

Radio-opaque materials in the form of shielding, partitions, or other configurations are used to help contain and control the emissions of radiation sources. See, e.g., U.S. Pat. Nos. 6,320,936 and 6,185,279, each of which is incorporated herein by reference in its respective entirety. The expense, size, weight, and/or performance of conventional shielding configurations for radiation sources remain a challenge. Health industries demand improvements in shielding strategies that would help attenuate fluence and lower the energy spectrum of the non-essential volume of the irradiated workspace. There also is a strong desire to reduce the extensive volume and mass of built-in peripheral shielding needed to meet regulatory requirements for operating equipment that contains harmful radiation sources. Preferably a shielding technique would be compatible with the delicate and temperature sensitive configurations of electronics and source assemblies such as x-ray tubes and the like.

There is a wide range of applications in which directed radiation emitted by an energy source is used to image or otherwise acquire information about a subject. Such applications may involve medical imaging systems that emit directed radiation toward a subject in order to capture corresponding image data. In representative uses, imaging data may be acquired from animals, including birds, mammals, reptiles, amphibians, insects, and the like. Most often, medical imaging is used to assess the health condition of zoo specimens, livestock, pets, and humans. Other applications may involve implanting medical devices that irradiate a desired target with radiation. An example would include implanting a medical device that emits directed radiation in order to destroy or otherwise damage a tumor or other undesired growth.

Still other applications may involve security assessment. Airport terminals, bus terminals, shipping terminals, train terminals, building egress, mail systems, and the like are examples where workers, passengers, equipment, and/or cargo may be remotely interrogated to assess whether such subjects might pose a security risk. High-traffic, security systems that use high energy radiation sources to inspect goods, cargo, luggage, passengers, workers, and other subjects if not adequately shielded pose a safety risk to users and subjects being scanned. A shielding technique that provides close containment of the radiation source and helps to restrict emitted radiation only to the subject of interest would be quite beneficial.

All such applications share in common the need to emit directed radiation toward a desired subject while attenuating or otherwise containing off-focus radiation.

SUMMARY OF THE INVENTION

The present invention provides radio-opaque coatings that provide radiation shielding for radiation sources. The coatings can be placed in close proximity to the source for close containment of off-focus radiation, thus helping to restrict the emitted radiation only to that radiation that is directed upon the subject of interest. Using techniques such as thermal spray techniques, the radio-opaque coatings can be provided even on thermally sensitive components, such as x-ray tubes, without undue risk of thermal damage. The coatings can be relatively thin and, yet, would help reduce the requirements placed upon additional partitions or shields that optionally may be used in combination with the shield coatings. The coatings, which can be made from a wide range of shielding materials or combinations of such materials, reduce the opportunity for scattered radiation to escape the partitions of an associated shielding configuration. With the benefit provided by the radio-opaque coatings, the volume of a shielding perimeter around an energy source can be reduced and/or rendered more secure. Principles of the present invention may be useful in a wide range of applications in which directed radiation is used to image or otherwise acquire information about a subject. Such applications may involve medical imaging systems that irradiate a desired target with radiation, and security assessment. In one aspect of the present invention, an imaging apparatus is provided. The imaging apparatus preferably comprises an energy transmissive envelope, a source of imaging energy housed in the energy transmissive envelope, and an energy shield coating provided on the energy transmissive envelope. The energy shield coating preferably comprises at least one port allowing passage of imaging energy therethrough toward at least one desired target to be imaged. The energy shield coating also preferably comprises at least one shielding material helping to shieldingly contain off-target energy outputted by the source.

In another aspect of the present invention, an imaging apparatus is also provided. The imaging apparatus comprises a source of imaging energy, and an energy shield coating positioned in a manner effective to help shield off target imaging energy outputted by the source. The energy shield coating comprises at least one port allowing passage of imaging energy therethrough toward at least one desired target to be imaged.

In another aspect of the present invention, a method of shielding a source of energy is provided. The method comprises the steps of thermally spraying a shielding composition onto an energy transmissive envelope and causing the source of energy to be positioned within the energy transmissive envelope.

BRIEF DESCRIPTION OF THE DRAWINGS The above mentioned and other advantages of the present invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic cross-section of a medical imaging device of the present invention incorporating shielding principles of the present invention;

Fig. 2 is a schematic cross-section of the x-ray tube used in the medical imaging device of Fig. 1 with strategic radio-opaque shielding coated onto the tube;

Fig. 3 is a schematic perspective view of the tube of Fig. 2;

Fig. 4 is a schematic cross-section of an implantable medical device incorporating shielding principles of the present invention;

Fig. 5 is a schematic illustration showing an alternative approach for shielding an energy source in accordance with the principles of the present invention;

Fig. 6 shows an illustrative apparatus for creating radio-opaque coatings of the present invention using thermal spray techniques; Fig. 7 is a front view of the thermal spray gun used in Fig. 6 showing the nozzle configuration; and

Fig. 8 is a schematic illustration of an alternative apparatus for creating radio-opaque coatings of the present invention using thermal spray techniques.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention.

Figs. 1 through 3 schematically show an approach of the present invention for helping to shield an energy source that might be used in medical imaging, implantable devices, security, or other applications in which directed radiation is emitted toward a subject while off-focus radiation is attenuated or otherwise contained by shielding. For purposes of discussion, Figs. 1 to 3 show this approach with respect to a representative medical imaging apparatus 10. Imaging apparatus 10 emits directed x-rays 12 toward a subject (not shown) for imaging purposes. Apparatus 10 implements a unique shielding configuration to help contain the off-focus x-rays 14 that is not directed toward the subject.

Imaging apparatus 10 includes an x-ray vacuum tube 16 positioned within housing 18. X-ray tube 16 serves as a source of x-rays 12 and 14 and includes an envelope 20 that helps to define an evacuated chamber 22. An anode 24 and cathode 26 are housed within chamber 22. Cathode 26 is spaced relative to the anode 24 within the envelope 20. The anode 24 and cathode 26 are maintained at a suitable differential voltage relative to each other, typically on the order of about 150 kV or less for medical imaging applications. In some modes of practice, the anode 24 may be maintained at ground, and the cathode may be maintained at a relatively high negative potential, e.g., -150 kV. In some alternative modes of practice, the anode 24 may be maintained at a positive potential, e.g., +75 kV, and the cathode may be maintained at a negative potential, e.g., -75 kV. Leads 28 and 29 are used to electrically couple anode 24 and cathode 26 to associated circuitry (not shown) external to x-ray tube 16 and/or apparatus 10.

Cathode 26 is configured with an electron focusing capability to emit and accelerate electrons at high speeds toward anode 24. A suitable target 30, e.g., a target comprising a metal material such as aluminum, is located in the path of the high energy electrons emitted by cathode 26. As shown, the target 30 is a separate component from either anode 24 or cathode 26. However, other configurations may be used. For instance, the target 30 may be integrated with the anode as described in U.S. Pat. No. 6,320,936 the entirety of which is incorporated herein by reference. The resultant impact of electrons upon target 30 outputs heat and x-rays 12 and 14. The x-rays 12 and 14 emitted from the target 30 are omnidirectional (including directed and undirected emissions). Thus, some directed x-rays 12 are emitted toward the desired subject to be imaged, while other undirected x-rays 14 are emitted in other directions.

To help contain the off-focus x-rays 14 emitted by x-ray tube 16, radio-opaque coating 32 providing radiation shielding capabilities is formed on envelope 20. The coating 32 includes port 34 allowing directed x-rays 12 to be emitted. In the meantime, coating 32 helps to contain and trap off-focus x-rays 14. The thermal spray process described further below allows low risk deposition of radio-opaque, molten metal to be deposited onto the otherwise delicate surface of tube 16 to form coating 32.

Coating 32 may be formed from any material or combination of materials that help provide coating 32 with radiation shielding characteristics. Radiation shielding relates to the use of a material(s) that can alter some characteristic of a source of particles and/or photons (such as spectrum, fluence, intensity, or the like) through physical interaction between the atomic structure of the atoms of the material and the incident photons or particles striking the material. The net reduction in such a characteristic of the incident particles or photons and any contribution by secondary radiation can be used to assess the shielding effectiveness of the material. Representative examples of materials with radiation shielding characteristics include elements having an atomic number of 39 or greater, preferably 56 or greater, more preferably 72 or greater, compounds of such elements, alloys incorporating such elements, admixtures incorporating such elements, combinations of these and the like. Elements with low atomic numbers (hydrogen and carbon, for example) also have the capacity to shield radiation effectively. However, it typically takes more material to provide effective shielding. Representative examples of preferred elements include Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi, and Ba. Heavier elements and materials incorporating such heavier elements, such as W, are more preferred singly or in combination as these tend to provide more shielding capability at a given coating thickness than lighter elements. Carbon-based materials such as polyethylene may also be used. Polyethylene, for instance, is a suitable shielding material inasmuch as polyethylene coatings are highly dense due to favorable packing density characteristics. A specific embodiment of coating 32 might include, for example, layers of tungsten, or a combination of tungsten and polyethylene as individual or multiple layers.

The thickness of coating 32 may vary over a wide range. As general guidelines, if coating 32 is too thin, then the ability of coating 32 to help contain energy may be less than is desired. Accordingly, the thickness of coating 32 is preferably chosen based on factors such as the coating composition, the nature of the radiation, energy, and/or signal to be shielded, and the amount of shielding or directing functionality desired by coating 32. For example, where coating 32 comprises Tungsten and the radiation source comprises a typical X-Ray spectrum used for dental examinations (10 to 100 KeV X-rays) coating 32 desirably may have a thickness of at least 10 micrometers, preferably 150 micrometers, more preferably at least 250 micrometers, even more preferably at least 500 micrometers. However, thicknesses of less than 10 micrometers may be used. On the other hand, if coating 32 is too thick, then the structural integrity of the coating and/or the internal stress of the coating may be affected. Generally, it is preferred that coating 32 has a thickness of up to 300 micrometers, desirably up to 150 micrometers, more desirably up to 100 micrometers. In any event, the thickness of coating 32 is determined based on the particular material composition used and the desired radiation blocking functionality for coating 32.

A considerable amount of heat typically is generated at the anode 24 during operation of x-ray tube 16, as is typical of x-ray tubes generally. Cooling media 36, typically an oil such as mineral oil, flows through chamber 22 to help remove heat and cool x-ray tube 16. Optionally, cooling media 36 may also flow through one or more of the cathode 26, anode 24, and/or target 30 to cool these component(s) to permit a higher x-ray output and to prevent overheating and thermal deformation of the component(s).

Radio-opaque member 38 having aperture 40 helps to provide an x-ray transmissive pathway 42 that extends from port 34 to x-ray transmissive window 44. This allows targeted x- rays 12 to reach the subject to be imaged. Pathway 42 may be evacuated, but more desirably is filled with an x-ray transmissive medium such as silicon oil or silicon gel. A gasket 46 helps to isolate pathway 42 from the surrounding cooling media in chamber 22. As shown, pathway 42 is generally cylindrical, but other geometries may be used if desired. For instance, the walls of aperture 40 may converge or diverge in a direction from port 34 to window 44.

In conventional imaging devices, the housing 18 in which x-ray tube 16 is positioned would be relied upon to provide a significant portion, if not all, of the shielding for containing off-focus x-rays 14 emitted from the x-ray tube 16. To be sufficiently radio-opaque for this purpose, conventional housings have tended to be bulky, thick, and/or heavy to provide adequate shielding. However, the use of radio-opaque shield coating 32 in accordance with the present invention permits housing 18 to be much less massive than if coating 32 were absent. Optionally, radio-opaque coatings similar to coating 32 may be applied to all or a portion of the surfaces of housing 18.

As an option, the surface of envelope 20 onto which coating 32 of the present invention is formed may be primed to improve adhesion. This may be accomplished by physically or chemically altering the surface of environment 20 via a technique such as corona, etching, ultraviolet, e-beam, x-ray, oxidation, reduction, heating, roughening, or other suitable treatment. Alternatively, a primer coating (not shown) constituting one or more priming materials in one or more priming layers may be used. As an example, a pre-coat of an organic, metallic, or ceramic material could be used to promote adhesion of a tungsten-containing material to envelope 20. Representative examples of primer materials include a highly-filled composite or metal/semi- metal silicates with an intermediate coefficient of thermal expansion (CTE) to ensure that there is relief in the CTE mis-match between the vacuum tube glass and the tungsten metal. These materials can be applied by chemical vapor deposition (CVD) or Radio frequency (RF) sputtering for the silicates or by paint or immersion for the composite pre-coat (e.g. acrylic w/titanium oxide filler).

As another option, coating 32 of the present invention may receive a post-treatment if desired. For example, the coating 32 may be polished following deposition to enhance gloss and surface finish as desired. In other modes of practice, the coating 32 may receive a protective overcoat (not shown) to protect the coating from damage, oxidation, or the like. Examples of materials that would be suitable to form an overcoat include reactive di-xylylene precursors applied by chemical vapor deposition, combinations of these, and the like. For implantable medical devices, the radiation shield coating may be overcoated with a biocompatible layer. In this regard, Fig. 4 schematically shows one representative embodiment of an implantable medical device intended to emit directed radiation 102 onto a substrate to be targeted for treatment. For purposes of illustration, the substrate is a tumor/cancer growth 104. Device 100 generally includes an envelope 106 housing a radiation source 108. The source 108 may emit radiation naturally and/or the radiation output may be electronically generated.

Combinations of energy sources may also be used. Directed radiation 102 is emitted toward growth 104 through radiation transmissive port 110. To help contain off-focus radiation, device 100 is shielded by coating 112 in accordance with principles of the present invention. Coating 112 includes port 114 to allow passage of the directed radiation 102.

Biocompatible layer 116 encapsulates coating 112, and layer 116 also includes a port 118 to allow passage of the directed radiation 102. Advantageously, the shield coating 112 tends to be naturally rough when applied using thermal spray techniques. This provides an excellent surface to which biocompatible layer 116 may adhere. At least that portion of the surface of biocompatible layer 116 proximal to ports 110, 114, and 118 may be polished as appropriate. Biocompatible layer 116 may be formed from a wide range of materials. Exemplary materials include bioglass, hydroxy-apatite, combinations of these, and the like. Fig. 5 shows an alternative approach of the present invention for helping to shield an energy source that might be used in medical imaging, implantable devices, security, or other applications in which directed radiation is emitted toward a subject while off-focus radiation is contained by shielding. An x-ray tube 200 includes envelope 202 defining an evacuated chamber 204. Anode 206, cathode 208, and target 210 are housed in the chamber 204. Leads 212 and 214 couple cathode 208 and anode 206 to corresponding circuitry (not shown).

Electrons 216 discharged from cathode 208 toward anode 206 impact target 210. This impact causes target 210 to emit omni-directional x-rays 218 and 220. X-rays 218 schematically represent x-ray energy emitted in a directed manner toward a subject (not shown) to be irradiated, while x-rays 220 schematically represent off-focus radiation emitted by target 210. To contain the off focus radiation, x-ray tube 200 is housed within cowling 222. The interior and/or exterior surfaces of cowling 222 advantageously are coated with a radiation shield coating of the present invention. The coating applied to cowling 222 includes an x-ray transmissive port 224 through which the directed x-rays 218 are emitted toward the subject to be irradiated. Fig. 5 shows an optional columnating tube 226 that may be used to help further focus x-ray energy emitted toward the subject. The exterior surfaces of the columnating tube 226 optionally may be coated with a radio-opaque shield coating provided in accordance with the present invention.

In preferred modes of practice, shield coatings of the present invention advantageously are formed on substrate surfaces using thermal spray techniques. The use of thermal spray techniques allows a coating to be formed on a wide range of substrates, including in particular temperature sensitive or delicate substrates, such as delicate x-ray tubes. Thermal spraying allows coatings to be formed without unduly thermally damaging such substrates. Generally, thermal spraying involves causing the substrate to be coated to pass through a plume of a spray comprising molten particles of the coating composition. In preferred modes of practice, a line of sight coating process uses heat energy to heat the coating material to a molten state. The molten material typically is caused to be atomized or otherwise converted into molten droplets. The molten material is carried to the substrate by a carrier gas or jet. The molten droplets are preferably finely sized. During coating, the substrate is moved in and out of the hot spray to minimize thermal risk to the substrate. The desired coating thickness desirably is built up using multiple passes. The substrate optionally may be thermally coupled to a heat sink and/or chilling media during thermal spraying in order to help carry away thermal energy imparted to the substrate.

One embodiment of a thermal spray system 300 useful to carry out thermal spraying is illustrated in Figs. 6 and 7. Particles, e.g., a fine powder, of a coating composition are supplied from a composition feedstock supply 302 to the thermal spray gun 304. The gun 304 is mounted on an X-Y positioning rack 306. Thermal spray gun 304 may be of a variety of types, including a flame gun, plasma gun, electric arc, gun or the like. For purposes of illustration, spray gun 304 is a flame-type gun. In such an embodiment, fuel and oxygen are supplied to the gun 304 from a fuel/oxidant supply 308 and air is supplied from an air supply 310. The air is ejected through annular nozzle 312, and the flame is emitted from nozzles 314 located centrally inside annular nozzle 312. The air carries entrained particles (not shown), which are melted by the flame 316 as the particles exit the gun 304. The air acts not only as a carrier gas to help transport the molten particles to the substrate (not shown) to be coated, but the air also acts as a nozzle coolant.

The molten particles are aimed at a pair of rotatable arms 318. The arm ends 320 each receive one or more corresponding substrates to be coated. By rotating arms 318, the substrates repeatedly move in an out of the spray plume. In this way, the thermal spray coating can be applied without excessively heating the substrates. Each substrate generally may be planar and may be fixedly mounted to an arm end 320. However, three-dimensional substrates such as x- ray tubes may also be coated. These would be mounted onto arms 318 so that the three dimensional substrate could be spun in several axis modes while the gun 304 sprays molten material onto the surfaces of the substrate in line of sight fashion.

The arms 318 are rotated by an electric motor 322. A coolant, such as compressed air, is pumped into the arms 318 from a coolant supply 324 through a pipe or hose 326 that connects to a coolant slip ring 328 located generally at the central axis of rotation of arms 318. The coolant flows from the slip ring to coolant passages (not shown) inside arms 318. Those passages desirably extend radially along the interior of arms 318 and each arm end 320.

The arms 318 rotate at a suitable rate, sweeping the mounted substrates through the spray of molten particles. As general guidelines, rotational rates within the range of 1 to 500 rpm, more desirably 300 to 350 rpm would be suitable. With each pass, the coating builds up on the surface(s) of the substrate in line of sight coating fashion. As a practical matter, the deposition of coating material tends to be a small swath along the substrate surfaces in the direction of rotation R, and as the arms 318 rotate. Accordingly, the gun 304 is indexed in the radial direction (X direction) with respect to the arms 318 so that the coating covers the entire surfaces to be coated. The speed of movement in the X direction optionally may be adjusted so that the deposition rate of material onto the substrate is constant. Otherwise, faster moving portions of the surfaces radially farther from the center of rotation may receive less material per unit time than those closer to the center of rotation.

The distance from the gun 304 to the arms 318 also is adjustable in the Y direction. In many embodiments, a desired distance is one at which substrate heating is below a desired threshold, yet the composition is still molten when it impacts the substrate. Thus, if gun 304 were to be too close to a substrate, the substrate might get too hot. If too far, the molten droplets might solidify too much before reaching the substrate surfaces, impairing the quality of the resultant coating. Fig. 8 schematically shows a thermal spray system 400 similar to system 300 of Figs. 6 and 7, except system 400 of Fig. 8 is adapted for automated processing of larger batches of substrates (not shown) in a protected environment 402 defined by housing 404. Particles, e.g., a fine powder, of a coating composition are supplied from a composition feedstock supply 406 to the thermal spray gun 408. A carrier gas supply (not shown) and heat energy source (not shown) such as fuel, electricity, or the like, are also coupled to gun 408. As shown, gun 408 is a plasma gun, facilitating thermal spraying of materials such as tungsten, which become molten at very high temperatures, e.g., temperatures above about 3,400 C. Supply 406 preferably includes an automated powder feeder that is outside environment 402 to facilitate convenient loading of powder feedstock. Gun 408 is generally aimed toward rotatable substrate mounting platform 410 including a plurality of arms 412 extending from centrally positioned rotor 414. Platform 410 rotates about central axis 416. System 400 also includes an exhaust system 418 includes a powder particulate collection system 420.

10 The movement of both gun 408 and rotatable substrate mounting platform 410 are automated and controlled via computer 422. An operator interfaces with the computer 422 and system 400 via console 424. Rotor 414 desirably has at least a computer-controlled rotation rate and rotation direction. Gun 408 is mounted on robotic manipulation system 426 which can control the distance between gun 408 and arms 412, the height of gun 408 relative to platform 410, the position of gun 408 relative to central axis 416, and the relative angle at which material is sprayed toward platform 410. The supply 406 of material to gun 408 is also automated and may be held constant or varied during the course of a coating operation as desired.

In a typical coating operation, the desired coating material is loaded into automated powder feeder of supply 406. One or more substrates (not shown) to be coated are positioned on one or more of arms 412. Desirably, the substrates are positioned in a balanced manner so that platform 410 rotates smoothly. Thus, pairs of substrates may be positioned in balanced fashion on opposed arms 412 symmetrically about central axis 416. If an odd number of substrates is being processed, a dummy substrate may also be used for balance. As is the case with arms 318 of apparatus 300 of Figs. 6 and 7, arms 412 of system 400 act as a heat sink to help draw thermal energy away from substrates being coated. Cooling media (not shown) desirably also is circulated through arms 412 to help cool the substrates.

The powder is supplied to gun 408 and is sprayed from gun 408 toward rotating platform 410. During spraying, platform 410 rotates at a suitable rotational speed, such as a speed in the range of 100 to 500 rpm. Typically, gun 408 may be indexed radially back and forth relative to platform 410 to help ensure full coverage of surfaces to be coated. The speed at which gun 408 is indexed may be adjusted based upon the position of gun 408 relative to central axis 416 so that coating coverage is uniform notwithstanding the changing relative speed between arms 412 and gun 408 as the radial position of gun 408 with respect to central axis 416 changes. The heat source, in this case a plasma, provides enough heat energy to melt the sprayed particles. Typically, the heat source provides a suitable temperature in the range of 7,000 C to about 20,000 C. The carrier gas is used transport the particles to the plasma heat source. The carrier gas may be a gas such as nitrogen, carbon dioxide, argon, air, combinations of these, and the like. A preferred plasma gas comprises argon (as a primary gas) and optionally at least one other gas such as hydrogen, helium, or nitrogen (As a secondary gas). A gas such as argon is favored because argon requires low ionization energy

A typical supply pressure for the carrier gas is in the range of 30 psi. The preferred primary (argon) and secondary gas (hydrogen) pressures are 75 psi and 50 psi respectively. The

11 molten particles impact on the substrates, where they coalesce and form a coating. Areas of the substrates may be masked if those areas are desired to be uncoated after treatment. A suitable process time may be in the range of a few seconds to 600 seconds or more. A satisfactory coating thickness generally would be in the range of 5 micrometers to about 500 micrometers. Excess spray material is exhausted through exhaust system 418, where entrained particles in the exhaust are collected.

Methods and equipment used to carry out thermal spraying suitable in the practice of the present invention also have been described in U.S. Pat. Nos. 5,762,711; 5,877,093; 6,110,537; 6,287,985; and 6,319,740. Each of these patent documents is incorporated herein by reference. Other embodiments of this invention will be apparent to those skilled in the art upon consideration of this specification or from practice of the invention disclosed herein. Various omissions, modifications, and changes to the principles and embodiments described herein may be made by one skilled in the art without departing from the true scope and spirit of the invention which is indicated by the following claims.

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Claims

WHAT IS CLAIMED IS:

1. An imaging apparatus, comprising:

a) an energy transmissive envelope; b) a source of imaging energy housed in the energy transmissive envelope; and c) an energy shield coating provided on the energy transmissive envelope, said coating comprising at least one port allowing passage of imaging energy therethrough toward at least one desired target to be imaged; and said coating comprising at least one shielding material helping to shieldingly contain off-target energy outputted by the source.

2. The imaging apparatus of claim 1 , wherein said envelope is an envelope of an x-ray tube.

3. The imaging apparatus of claim 1 , wherein said envelope is evacuated.

4. The imaging apparatus of claim 1 , wherein the imaging energy comprises x-rays.

5. The imaging apparatus of claim 1 , wherein the shielding material comprises tungsten.

6. The imaging apparatus of claim 1 , wherein the shielding material comprises copper- coated tungsten carbide.

7. The imaging apparatus of claim 1 , wherein the shielding material comprises titania or tungsten oxide filled acrylic ester.

8. The imaging apparatus of claim 1 , further comprising programming that helps to manipulate image data obtained from a mammal.

9. The imaging apparatus of claim 1 , further comprising programming that helps to manipulate image data obtained from a human.

10. The imaging apparatus of claim 8, wherein said image data is indicative of a health condition of the mammal.

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11. The imaging apparatus of claim 8, wherein said image data is indicative of a security risk of the mammal.

12. The imaging apparatus of claim 1 , further comprising programming that helps to manipulate image data obtained from a target.

13. The imaging apparatus of claim 12, wherein said image data is indicative of a security risk of the target.

14. The imaging apparatus of claim 12, wherein the target is a mammal.

15. The imaging apparatus of claim 12, wherein the target is a container.

16. An imaging apparatus, comprising:

a) a source of imaging energy; and b) an energy shield coating positioned in a manner effective to help shield off target imaging energy outputted by the source, said coating comprising at least one port allowing passage of imaging energy therethrough toward at least one desired target to be imaged.

17. A method of evaluating a target, comprising the steps of using the imaging apparatus of claim 16 to acquire image data associated with the target; and using the image data to assess a condition of the target.

18. The method of claim 17, wherein the target is a mammal.

19. The method of claim 17, wherein the target is a container.

20. The method of claim 17, wherein the image data is a mammal and the image data is used to assess a health condition of the mammal.

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21. The method of claim 17, wherein said condition is a security risk associated with the target.

22. The method of claim 17, wherein said condition is a health condition associated with the target.

23. A method of shielding a source of energy, comprising the steps of thermally spraying a shielding composition onto an energy transmissive envelope; and causing the source of energy to be positioned within the energy transmissive envelope.

24. The method of claim 23, wherein the source of energy is positioned within the transmissive envelope prior to thermal spraying.

25. The method of claim 23, wherein the source of energy is positioned within the transmissive envelope after thermal spraying.

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