A GAMMA-RAY SOURCE FOR USE IN RADIOGRAPHY

Abstract: A gamma-ray source (10) suitable for use with apparatus for producing a radiographic image of an object, includes a body (12) which includes a radioisotope material. The body (12) has a gamma-ray emission surface (14) which has an emission area which is at least one and a quarter times greater than its projected area.

Description: A GAMMA-RAY SOURCE FOR USE IN RADIOGRAPHY THIS INVENTION relates to radiography. In particular, it relates to radiography by making use of radioisotope material emitting gamma-rays. The use of gamma-ray radiography in medical or veterinary diagnostics requires the balancing of image definition against exposure time. This requires a gamma-ray source which is small enough to ensure adequate image definition yet is active enough to require an acceptably small exposure time. It is an object of this invention to provide a gamma-ray source which can yield useful results in medical and veterinary diagnostic applications. According to a first aspect of the invention, there is provided a gamma-ray source suitable for use with apparatus for producing a radiographic image of an object, the source including a body which includes a radioisotope material, the body having a gamma-ray emission surface which has an emission area which is at least one and a quarter times greater than its projected area. The gamma-ray emission surface may be uneven. The unevenness of the emission surface of the body may be provided by corrugations. Preferably, the pitch of the corrugations is at the most four times the thickness of the body. More preferably, the pitch of the corrugations is twice the thickness of the body. Instead, in one embodiment of the invention, the unevenness of the emission surface of the body may be provided by a plurality of wire-like elements which include the radioisotope material, the wire-like elements being closely packed in side by side relationship The corrugations and/or the wire-like elements may be concentrically arranged, or they may be linearly arranged parallel to each other The corrugations may have a semi-circular, saw tooth, sinusoidal or any other profile in section which produces an effective increase in the emission area of the body. In another embodiment, the unevenness of the emission surface of the body is provided by an elongate wire-like element which includes the radioisotope material, the wire-like element being arranged in a spiral. In yet another embodiment of the invention, the unevenness of the emission surface of the body may be provided by a plurality of beads which include the radioisotope material, the beads being closely packed against each other. The beads may have a maximum transverse dimension of 2mm. The beads may be packed in concentric rings or in parallel strip Preferably, the beads are packed in a close hexagonal arrangement The beads may be spherical or half-spherical. The body may be square or rectangular in plan view. Preferably, the body is circular in plan view, and may have a convex or concave gamma-ray emission surface. The body may have a thickness of between 0,25mm and 5mm and a diameter between 3mm and 40mm The body may be in the form of a hollow hemi-spheπcal dome, the gamma-ray emission surface being provided by an inside surface of the dome Such a dome has a disc-shaped projected area The inside surface of the hemi- spherical dome may then be uneven to further increase the emission area of the emission surface. Instead, the body may be annular, the source including a disc which includes a material with an atomic number between 40 and 74, and the disc covering the opening in the annular body. Such a source provides backscattered 60 keV gamma-rays as well as X-ray fluorescence of energy characteristic of the material with an atomic number between 40 and 74, the rays being radiated through the opening of the annular body. Such a gamma-ray source utilising backscattered radiation may be used for obtaining radiographic images of thin objects which requires soft X-rays. The source may include a substrate for the body on a side of the body remote from the gamma-ray emission surface of the body. The substrate may be preformed and may be of a metal selected from the metals with an atomic number between 40 and 74, such as tungsten . The substrate may also include a layer of a material with an atomic number less than 40. If a material with an atomic number of less than 40 is used, the material is preferably graphite. The substrate may comprise at least two layers, a first layer having a high gamma-ray absorption but a low gamma-ray scattering tendency, such as tungsten, and a second layer having a low gamma-ray absorption but a high gamma-ray scattering tendency, such as iron or carbon, the second layer being sandwiched between the first layer and the body. The source may include a gamma-ray impermeable housing for at least the body, the housing having a metal window covering the gamma-ray emission surface of the body, and permitting the passage of gamma-rays. Typically, the housing encloses the body and the substrate, the body thus being sandwiched between the substrate and the window. The housing may be selected from the group consisting of aluminium, copper and stainless steel, and the metal of the window may be selected from the group consisting of beryllium, stainless steel, aluminium, and silver. The window may have a thickness of half a millimetre at the most. The window is typically 0,2 to 0,25mm thick or somewhat thinner if silver is used . The radioisotope material may be in the form of an oxide. The oxide may be in admixture with a ceramic material which allows gamma-rays emitted by the radioisotope material to escape The admixture may be sintered . The body may include an additive with an atomic number between 40 and 70 and having a characteristic X-ray emission of between 1 8 and 59 keV. However, neutron producing elements such as Be and F, must be excluded from the admixture. The source may have an activity of at least 0, 1 Curie and at most 20 Curie, particularly for medical or veterinary diagnostic applications, and may have a source loading of at least 8 mCuπe/mm 2 . The radioisotope material may be selected from the group consisting of amerιcιum-241 ( 241 Am) , thulιum-1 70 ( 170 Tm) , and mixtures thereof. According to a second aspect of the invention, there is provided a method of radiographing an object for medical or veterinary diagnostic purposes, the method including the steps of placing an object to be radiographed between radiographic image capturing means and a gamma-ray source which includes amerιcιum-241 ( 241 Am) as a radioisotope material; and exposing the object to gamma-rays emitted by the gamma-ray source for a period of time effective to capture a radiographic image of the object on the radiographic image capturing means, the radiographic image capturing means including a charge-coupled or back entrance charge-coupled device camera, the method including the steps of applying analogue or digital image processing techniques to the radiographic image of the object captured by the camera and displaying the radiographic image on a viewing monitor. According to a third aspect of the invention, there is provided a method of radiographing an object for medical or veterinary diagnostic purposes, the method including the steps of placing an object to be radiographed between radiographic image capturing means and a gamma-ray source as hereinbefore described; and exposing the object to gamma-rays emitted by the gamma-ray source for a period of time effective to capture a radiographic image of the object on the radiographic image capturing means According to a fourth aspect of the invention, there is provided a method of radiographing an object, which includes the steps of placing an object to be radiographed between radiographic image capturing means and a gamma-ray source as hereinbefore described; and exposing the object to gamma-rays emitted by the gamma-ray source for a period of time effective to capture a radiographic image of the object on the radiographic image capturing means. The method of the invention may include locating the radiographic image capturing means as close as possible to the object which is to be radiographed, thereby to improve the sharpness of the radiographic image of the object produced on the radiographic image capturing means. The method may include at least partially shielding the radiographic image capturing means from scattered environmental radiation by locating a shield of gamma-ray absorbing material on a side of the radiographic image capturing means remote from the object. Examples of such materials are lead and cerrobend alloy, which comprises lead, bismuth and cadmin. The method may also include, when used in medical or veterinary diagnostic work, protecting the patient by placing a lead-filled or a cerrobend alloy-filled cloth over parts of the patient's body which is not to be radiographed . instead, cast shields of lead or cerrobend alloy, cast into desired shapes, may be used . The method and source may also be used for dental applications. Thus, the method may include locating the gamma-ray source inside the mouth of a patient and locating the radiographic image capturing means outside the mouth of the patient, thereby radiating outwards with the gamma-ray source to limit radiation exposure to the patient The method may include the step of processing the radiographic image of the object on the capturing means to produce a visible radiographic image of the object. Thus, in the case of the radiographic image capturing means being radiographic film, the processing may include developing the radiographic film. Instead, the processing may include converting an image from a fluoroscopic screen, coupled to an image intensifying device or tube and a charge-coupled device camera to yield electrical signals and displaying the image on a viewing monitor. The radiographic image capturing means may thus include a charge- coupled or back entrance charge-coupled device camera. The method may accordingly include the steps of applying analogue or digital image processing techniques, such as frame addition and frame integration, known to those skilled in the art, to the radiographic image of the object captured by the camera and displaying the radiographic image on a viewing monitor. Preferably, the digital image processing technique is frame integration. According to a fifth aspect of the invention, there is provided a method of manufacturing a gamma-ray source, the method including the step of sintering a radioactive layer of an admixture of a ceramic material and a gamma- ray emitting radioisotope material onto a shaped non-planar surface of a substrate, the non-planar surface of the substrate having a surface area which is at least one and a quarter times greater than its projected area. The method may include sandwiching the radioactive layer between the substrate and a lid of a low gamma-ray absorbing material . According to a sixth aspect of the invention, there is provided a method of manufacturing a gamma-ray source, the method including sintering an admixture of a ceramic material and a gamma-ray emitting radioisotope material to provide a plurality of gamma-ray emitting components; and mounting the gamma-ray emitting components on a substrate to provide a gamma-ray source with an uneven gamma-ray emission surface. The components may be in the form of wire-like elements, the method including mounting the wire-like elements in a closely packed side-by- side relationship on the substrate Instead, the components may be in the form of beads, the method including mounting the beads in a closely packed hexagonal arrangement on the substrate. The radioisotope material may be as hereinbefore described . The method of manufacturing may also include the step of enclosing the body in a metal such as stainless steel. The method of manufacturing may include covering the sintered ceramic layer with a low gamma-ray absorbing material such as alumina. According to a seventh aspect of the invention, there is provided apparatus for producing a radiographic image of an object, the apparatus including a gamma-ray source as hereinbefore described; and radiographic image capturing means spaced from the gamma-ray source for capturing a radiographic image of the object, the spacing between the source and the radiographic image capturing means being sufficient to accommodate the object operatively between them The radiographic image capturing means may include in combination a fluoroscopic screen coated with, for example, silver-activated zinc cadmium sulphide or terbium-activated gadolinium oxysulphide, coupled to an image intensifying device or tube coated with, for example, caesium iodide, for intensifying an optical image of the object captured by the fluoroscopic screen. The radiographic image capturing means may further include a charge-coupled device camera for converting the optical image from the image intensifying device or tube into an electronic signal. Thus, the charge-coupled device camera may have a chip comprising an array of charge-coupled device elements for display of the image Instead, the radiographic image capturing means may include in combination a fluoroscopic screen coupled to a back entrance charge-coupled device camera. In one embodiment of the invention, the radiographic image capturing means includes a charge-coupled device camera, the charge-coupled device camera having a chip comprising an array of charge-coupled device elements coated with a fluorescent material The charge-coupled device camera may be a back entrance charge-coupled device camera. Such charge-coupled device cameras, coated with a fluorescent material, are expected to have particular application in obtaining radiographic images of small objects, such as in dental applications The array may be arranged in a layout selected from the group consisting of a square layout, a linear layout, an L-shaped layout, and a curved layout By providing a controlled, cyclic motion for arrays of such linear, L-shaped or curved charge-coupled device elements, a slice-by slice image of an object may be captured, e.g . as in baggage scanners The radiographic image capturing means may include a non-screen type radiographic film. Alternatively, the radiographic image capturing means may include in combination a screen type radiographic film and an intensifying screen, using intensifying screens and film such as UV-rapid X-ray film. Blue sensitive or green sensitive X-ray film may also be used. The apparatus may include a C-shaped frame, the gamma-ray source being mounted on one end of the frame and the radiographic image capturing means being mounted on the other end of the frame. Instead, the apparatus may include a portable stand, such as a tripod, for supporting the gamma-ray source in a spaced relationship with the object to be radiographed . A further option is that the apparatus may be used in similar fashion to conventional X-ray apparatus, to the extent that the gamma-ray source may be used in place of the X-ray tube arrangement of the X-ray apparatus. The apparatus may include a portable power source for powering electronic components of the apparatus. The method and apparatus of the invention may be used for medical diagnostic or veterinary diagnostic work The Applicant believes that the invention will find particular, though not necessarily exclusive, application in areas where there is no or an inadequate electricity supply system, for example to diagnose battlefield injuries or injuries received as a result of a vehicle accident, at the scene of a battle or an accident The apparatus may then include a battery or other portable power supply as mentioned above to drive a safety lock or a shutter Even image processing apparatus such as a computer may be driven by a battery or a portable generator Furthermore, the method and apparatus of the invention may be used in industrial applications such as quality control during manufacturing of plastic articles, electronic circuit boards and articles of aluminium or articles having thin metal walls such as pens, and in security applications such as controlling diamond or drug smuggling or illegal trafficking in explosives The method and apparatus of the invention may also be used for scanning baggage at airports If desired, the gamma-ray source may then have a body in the form of a col mated line source comprising the radioisotope material. In addition, the method and apparatus of the invention may be used for computer aided tomography If desired, the gamma-ray source may then have a body in the form of a circular or elliptical wire. The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which Figure 1 shows schematically apparatus according to the invention for producing a radiographic image of an object; Figure 2 shows schematically a machine head for the apparatus of Figure 1 ; Figure 3 shows a sectioned elevation of a gamma-ray source in accordance with the invention; Figure 4 shows in elevation one embodiment of apparatus according to the invention for producing a radiographic image of an object ; Figure 5 shows in elevation another embodiment of apparatus according to the invention for producing a radiographic image of an object; and Figure 6 shows schematically one embodiment of a radiographic image capturing means in accordance with the invention Referring to Figure 1 of the drawings, reference numeral 200 generally indicates apparatus for producing a radiographic image of an object The apparatus 200 comprises a machine head 1 1 which houses a gamma-ray source (not shown), a radiographic image capturing means 80 spaced from the machine head 1 1 , and an output system 1 80 for providing the required radiographic information for an object 54 which is to be radiographed . The object 54 is located between the source of the machine head 1 1 and the radiographic image capturing means 80. Gamma-rays 56 are emitted from the machine head 1 1 as a col mated beam and passes through the object 54 onto the radiographic image capturing means 80. The machine head is a distance d from the object 54. Referring to Figure 2 of the drawings, the machine head 1 1 is shown in more detail. The machine head 1 1 comprises a shielded housing 71 which houses a gamma-ray source 1 0 in accordance with the invention. The shielded housing 71 provides adequate shielding to render use of the gamma-ray source 10 safe. The housing 71 has an aperture 73 through which gamma-rays emitted by the gamma-ray source 1 0 can be directed at an object 54 to be radiographed . A shutter 1 5 displaceable between an open and a closed condition is located over the aperture 73, between the gamma-ray source 1 0 and the aperture 73. The shutter 1 5 prevents leakage of gamma-rays when the apparatus 200 is not used . A control device 1 20 controls operation of the shutter 1 5 during gamma-ray exposure of the object 54. Referring more particularly to Figure 3 of the drawings, the gamma- ray source 1 0 has a solid body 1 2 which includes amerιcιum-241 radioisotope material ( 241 Am) in the form of ameπcium oxide in admixture with a ceramic component. A gamma ray emission surface 1 4 of the body 1 2 is uneven. The unevenness of the emission surface 1 4 is provided by corrugations 1 2.1 which provide an increased surface area for the body 1 2 and hence gamma-ray emissions are increased . In plan view (not shown) the gamma-ray source 1 0 is circular. Thus, the body 1 2 is in the form of a rippled or corrugated disc having transverse linear corrugations 1 2. 1 and having a diameter D of about 1 8mm. The body 1 2 has a thickness T of about 2mm. The pitch of the corrugations is about 4mm. The body 1 2 is formed on a substrate 1 6 of graphite. The substrate 1 6 has an inverted pan-shaped tungsten alloy backing layer 1 7. The substrate 1 6 also has a corrugated surface 1 8 Thus, the corrugated emission surface 1 4 of the body is formed by sintering the ceramic admixture which includes the amerιcιum-241 radioisotope material onto the corrugated surface 1 8 of the substrate 1 6. The body 1 2, the substrate 1 6 and the tungsten alloy backing layer 1 7 are enclosed by a stainless steel ring 20. The ring 20 has a thickness R of about 2mm. A stainless steel window 22 is integrally formed with the ring 20 or is welded to the ring 20 and covers the emission surface 14 of the body 1 2. The window 22 has a thickness P of about 0,25mm The purpose of the window 22 is to contain the radioactive amencium oxide inside the gamma-ray source 1 0 A solid cylindrical grip 24 protrudes centrally from the tungsten alloy backing layer 1 7 The grip 24 is also of stainless steel A stainless steel backing plate 1 5 covers the tungsten alloy backing layer 1 7 The grip 24 serves to simplify handling of the source 1 0 during positioning in the machine head 1 1 of Figure 1 Referring to Figure 4 of the drawings, reference numeral 300 shows another embodiment of apparatus for producing a radiographic image of an object, and unless otherwise indicated , the same reference numerals used above are used to designate the same or similar parts or features. A lead shield 70 is located between the object 54 and a horizontal support surface 52 The lead shield 70 reduces the effect of scattered gamma- ray radiation from the ground on the radiographic image capturing means 80. Referring to Figure 5 of the drawings, reference numeral 400 shows yet another embodiment of apparatus for producing a radiographic image of an object, and unless otherwise indicated, the same reference numeral used above are used to designate the same or similar parts or features. In contrast to the apparatus 300 of Figure 4, the apparatus 400 of Figure 5 does not include a horizontal support. The gamma-rays 56 are beamed generally horizontally in contrast to the generally vertically gamma-rays 56 of Figure 4. Referring to Figure 6 of the drawings, the radiographic image capturing means 80 includes a fluorescent screen 90. An optical beam directing device 85 directs the light from the screen 90 into a lens system 60 which focuses the light onto a charge-coupled device camera 95 The output from the camera 95 goes to a processing device 1 00, which is controlled by a controller 1 90. The processing device 1 00 can display analogue or digital images on a monitor screen 1 1 0 An output control system 1 50 can direct the output from the processing device 1 00 to the screen 1 1 0, or to a data saving device 1 30 or to a hard copy output device 1 40, or to two ore more of these devices together. In use, the object 54 is exposed to the gamma-ray source 1 0 by opening the shutter 1 5 via the control device 1 20 for a desired period of time. This period of time is determined by the geometry of the object 54 and the distance d . Because image sharpness is reduced by decreased object 54 to machine head 1 1 distance d, but exposure time to gamma-ray radiation to obtain a useful image is increased by increased object 54 to machine head 1 1 distance d, the machine head 1 1 is located at an optimum distance from the object. A suitable radiographic image capturing means 80 such as described above is located as close to the object 54 as possible on the remote side of the object relative to the machine head 1 1 . The gamma-ray source 1 0 is shielded from the object by the shutter 1 5 (not shown) until the object 54 is to be radiographed, whereafter the shutter 1 5 is opened for an effective period of time to produce a radiographic image by means of the radiographic image capturing means 80. Without wishing to be bound by theory, the Applicant believes that increased loading, that is increased activity of an amerιcιum-241 gamma-ray source by increasing the thickness of the body of radioisotope containing ceramic material, or the concentration of the radioisotope material in the ceramic body, is not cost effective beyond a certain thickness or concentration, due to the self-absorbtion of the 60 keV gamma-rays emitted by the amerιcιum-241 radioisotope material. Thus, the Applicant believes that a four-fold increase in the thickness of a conventional body, (i.e. a four-fold increase in the mass of americιum-241 radioisotope present in the body) only increases the gamma-ray emission from the source by two to three times. By increasing the size of the gamma-ray source, e.g. by increasing the diameter of a disc-shaped body of a gamma-ray source, the sharpness of a radiographic image of an object produced by the gamma-ray source is negatively affected However, the Applicant believes that by increasing the emission surface area of the body comprising the radioisotope material, for the same body thickness, mass of amerιcιum-241 radioisotope and diameter, an increase in gamma-ray emission of about three times can be achieved By also optimizing the source loading in conjunction with increasing the surface area of the body, even better results are possible By selecting an optimum object to gamma-ray source distance and by using a suitable image capturing means such as UV-rapid X-ray film and locating the film as close as possible to the object to be radiographed; or by electronically enhancing the radiograph image produced by the gamma-ray source on a fluoroscopic screen or by a charge-coupled device camera, the Applicant believes that it is practical to use a gamma-ray source comprising amerιcιum-241 radioisotope material for medical and veterinary diagnostic work and industrial applications. The optimum configuration for minimum exposure time and maximum sharpness can be determined by a person skilled in the art using routine experimentation. The Applicant also believes that it is possible further to reduce exposure times when using a gamma-ray source according to the invention if the body of the gamma-ray source is in the form of a hollow hemi-spheπcal dome with an uneven gamma-ray emission surface. The Applicant believes that the ameπcιum-241 radioisotope material, emitting 26 keV and 60 keV gamma-rays, is well suited for medical and veterinary diagnostic work and that a gamma-ray source comprising ameπcium- 241 radioisotope material emits gamma-rays which in their effect, when producing a radiographic image, is equivalent to the effect of a 65 kV to 70 kV X-ray machine. It is an advantage that the apparatus of the invention can be portable or transportable, particularly since no transformer is required to power the apparatus as in conventional X-ray equipment. The Applicant believes that exposure times of as little as a few seconds producing acceptable quality radiographic images of some parts of a human or animal body for medical or veterinary diagnostic work are obtainable with the gamma-ray source of the invention. It is yet another advantage of the gamma-ray source of the invention, when amerιcιum-241 is used as the radioisotope material, that it emits mostly 60 keV gamma radiation, which is well suited for some types of medical and veterinary diagnostic work.

Claims: CLAIMS 1 A gamma-ray source suitable for use with apparatus for producing a radiographic image of an object, the source including a body which includes a radioisotope material, the body having a gamma-ray emission surface which has an emission area which is at least one and a quarter times greater than its projected area 2. A source as claimed in claim 1 , in which the gamma-ray emission surface is uneven. 3. A source as claimed in claim 2, in which the unevenness of the emission surface of the body is provided by corrugations 4. A source as claimed in claim 3, in which the pitch of the corrugations is at the most four times the thickness of the body 5. A source as claimed in claim 4, in which the pitch of the corrugations is twice the thickness of the body 6. A source as claimed in claim 2, in which the unevenness of the emission surface of the body is provided by a plurality of wire-like elements which include the radioisotope material, the wire-like elements being closely packed in side by side relationship. 7 A source as claimed in claim 2, in which the unevenness of the emission surface of the body is provided by an elongate wire-like element which includes the radioisotope material, the wire-like element being arranged in a spiral. 8. A source as claimed in claim 2, in which the unevenness of the emission surface of the body is provided by a plurality of beads which include the radioisotope material, the beads being closely packed against each other. 9. A source as claimed in claim 8, in which the beads have a maximum transverse dimension of 2mm. 10. A source as claimed in claim 8 or claim 9, in which the beads are packed in a close hexagonal arrangement 1 1 . A source as claimed in any one of claims 1 to 1 0 inclusive, in which the body is circular in plan view, with a convex or concave gamma-ray emission surface. 1 2. A source as claimed in claim 1 1 , in which the body has a thickness of between 0,25mm and 5mm and a diameter between 3mm and 40mm. 1 3. A source as claimed in any one of claims 1 to 10 inclusive, in which the body is in the form of a hollow hemi-spheπcal dome, the gamma-ray emission surface being provided by an inside surface of the dome. 14. A source as claimed in any one of claims 1 to 1 0 inclusive, in which the body is annular, the source including a disc which includes a material with an atomic number between 40 and 74, the disc covering the opening in the annular body. 1 5. A source as claimed in any one of the preceding claims, which includes a substrate for the body on a side of the body remote from the gamma-ray emission surface of the body. 1 6. A source as claimed in claim 1 5, in which the substrate comprises at least two layers, a first layer having a high gamma-ray absorption but a low gamma- ray scattering tendency, and a second layer having a low gamma-ray absorption but a high gamma-ray scattering tendency, the second layer being sandwiched between the first layer and the body. 1 7. A source as claimed in any one of the previous claims, which includes a gamma-ray impermeable housing for at least the body, the housing having a metal window covering the gamma-ray emission surface of the body, and permitting the passage of gamma-rays. 1 8. A source as claimed in claim 1 7, in which the housing is selected from the group consisting of aluminium, copper and stainless steel, and the metal of the window is selected from the group consisting of beryllium, stainless steel, aluminium, and silver. 1 9 A source as claimed in claim 1 8, in which the window has a thickness of half a millimetre at the most 20. A source as claimed in any one of the preceding claims, in which the radioisotope material is in the form of an oxide and in which the oxide is in admixture with a ceramic material. 21 . A source as claimed in any one of the preceding claims, in which the body includes an additive with an atomic number between 40 and 70 and having a characteristic X-ray emission of between 1 8 and 59 keV. 22. A source as claimed in any one of the preceding claims, which has an activity of at least 0, 1 Curie and at most 20 Curie. 23. A source as claimed in any one of claims 1 to 21 inclusive, which has a source loading of at least 8 mCuπe/mm 2 . 24. A source as claimed in any one of claims 1 to 23 inclusive, in which the radioisotope material is selected from the group consisting of ameπcιum-241 ( 241 Am) , thulιum-1 70 ( 170 Tm) , and mixtures thereof. 25. A method of radiographing an object for medical or veterinary diagnostic purposes, the method including the steps of placing an object to be radiographed between radiographic image capturing means and a gamma-ray source which includes americium-241 ( 241 Am) as a radioisotope material; and exposing the object to gamma-rays emitted by the gamma-ray source for a period of time effective to capture a radiographic image of the object on the radiographic image capturing means, the radiographic image capturing means including a charge-coupled or back entrance charge-coupled device camera, the method including the steps of applying analogue or digital image processing techniques to the radiographic image of the object captured by the camera and displaying the radiographic image on a viewing monitor. 26. A method of radiographing an object for medical or veterinary diagnostic purposes, the method including the steps of placing an object to be radiographed between radiographic image capturing means and a gamma-ray source as claimed in any one of claims 1 to 24 inclusive; and exposing the object to gamma-rays emitted by the gamma-ray source for a period of time effective to capture a radiographic image of the object on the radiographic image capturing means. 27. A method of radiographing an object, which includes the steps of placing an object to be radiographed between radiographic image capturing means and a gamma-ray source as claimed in any of claims 1 to 24 inclusive; and exposing the object to gamma-rays emitted by the gamma-ray source for a period of time effective to capture a radiographic image of the object on the radiographic image capturing means 28 A method as claimed in any one of claims 25 to 27 inclusive, which includes at least partially shielding the radiographic image capturing means from scattered environmental radiation by locating a shield of gamma-ray absorbing material on a side of the radiographic image capturing means remote from the object. 29. A method as claimed in any one of claims 25 to 28 inclusive, in which the gamma-ray source is located inside the mouth of a patient and the radiographic image capturing means is located outside the mouth of the patient. 30. A method as claimed in claim 26 or claim 27, in which the radiographic image capturing means includes a charge-coupled or back entrance charge- coupled device camera, the method including the steps of applying analogue or digital image processing techniques to the radiographic image of the object captured by the camera and displaying the radiographic image on a viewing monitor. 31 . A method as claimed in claim 25 or claim 30, in which the digital image processing technique is frame integration 32 A method of manufacturing a gamma-ray source, the method including the step of sintering a radioactive layer of an admixture of a ceramic material and a gamma-ray emitting radioisotope material onto a shaped non-planar surface of a substrate, the non-planar surface of the substrate having a surface area which is at least one and a quarter times greater than its projected area 33 A method as claimed in claim 32, which includes sandwiching the radioactive layer between the substrate and a lid of a low gamma-ray absorbing material. 34. A method of manufacturing a gamma-ray source, the method including sintering an admixture of a ceramic material and a gamma-ray emitting radioisotope material to provide a plurality of gamma-ray emitting components; and mounting the gamma-ray emitting components on a substrate to provide a gamma-ray source with an uneven gamma-ray emission surface. 35. A method as claimed in claim 34, in which the components are in the form of wire-like elements, the method including mounting the wire-like elements in a closely packed side-by-side relationship on the substrate. 36. A method as claimed in claim 34, in which the components are in the form of beads, the method including mounting the beads in a closely packed hexagonal arrangement on the substrate. 37 A method as claimed in any one of claims 32 to 36 inclusive, in which the radioisotope material is selected from the group consisting of amerιcιum-241 ( 2 1 Am) , thulιum- 1 70 ( 170 Tm) , and mixtures thereof. 38. Apparatus for producing a radiographic image of an object, the apparatus including a gamma-ray source as claimed in any one of claims 1 to 24 inclusive; and radiographic image capturing means spaced from the gamma-ray source for capturing a radiographic image of the object, the spacing between the source and the radiographic image capturing means being sufficient to accommodate the object operatively between them. 39. Apparatus as claimed in claim 38, in which the radiographic image capturing means includes in combination a fluoroscopic screen coupled to an image intensifying device for intensifying an optical image of the object captured by the fluoroscopic screen. 40. Apparatus as claimed in claim 39, in which the radiographic image capturing means further includes a charge-coupled device camera for converting the optical image from the image intensifying device into an electronic signal. 41 Apparatus as claimed in claim 38, in which the radiographic image capturing means includes in combination a fluoroscopic screen coupled to a back entrance charge-coupled device camera 42 Apparatus as claimed in claim 38, in which the radiographic image capturing means includes a charge-coupled device camera, the charge-coupled device camera having a chip comprising an array of charge-coupled device elements coated with a fluorescent material 43. Apparatus as claimed in claim 42, in which the charge-coupled device camera is a back entrance charge-coupled device camera. 44. Apparatus as claimed in claim 42 or 43, in which the array is arranged in a layout selected from the group consisting of a square layout, a linear layout, an L-shaped layout, and a curved layout. 45. Apparatus as claimed in claim 38, in which the radiographic image capturing means includes in combination a screen type radiographic film and an intensifying screen. 46. Apparatus as claimed in any one of claims 38 to 45 inclusive, which includes a C-shaped frame, the gamma-ray source being mounted on one end of the frame and the radiographic image capturing means being mounted on the other end of the frame. 47. Apparatus as claimed in any one of claims 38 to 45 inclusive, which includes a portable stand for supporting the gamma-ray source in a spaced relationship with the object to be radiographed 48. Apparatus as claimed in any one of claims 38 to 47 inclusive, which includes a portable power source for powering electronic components of the apparatus. 49. A gamma-ray source as claimed in claim 1 , substantially as herein described and illustrated 50. A method of radiographing an object as claimed in claim 25 or claim 26 or claim 27, substantially as herein described and illustrated . 51 . A method of manufacturing a gamma-ray source as claimed in claim 32 or claim 34, substantially as herein described and illustrated . 52. Apparatus as claimed in claim 38 for producing a radiographic image of an object, substantially as herein described and illustrated . 53. A new gamma-ray source, method or apparatus, substantially as herein described.

Inventors: JOUBERT GIDEON JACOBUS JOHANNE, JOUBERT, GIDEON, JACOBUS, JOHANNES
Applicants: JOUBERT GIDEON JACOBUS JOHANNE, JOUBERT, GIDEON, JACOBUS, JOHANNES
Application year: 1999
Main classification: G21G4
IPC codes: G21G4