US 3719823 A
Description (OCR text may contain errors)
States tent Sheldon 51 March 6, 1973  RADIO-ISOTOPE CAMERAS USING 3,375,388 3/1968 Sheldon ..3l3/65 s VACUUM TUBES WITH FIBEROPTIC 3,422,232 Z1329 Sheld0ln ..250/83v/38l3;lP 3,4 01 l 9 Stemg ass ..250 .3 g gg gggg ggg ggggg B 3,021,834 2/1962 Sheldon ..250/213 VT CONSTRUCTION 3,225,193 12/1965 Hilton et al ..250/71.5 s  Inventor: Edward Emanuel Sheldon, 30 East P E A R B h It 40th Stre t, Ne Y k, N.Y. 10016 e e w or AtrorneyPolachek & Saulsbury  Filed: Aug. 20, 1969 21 Appl. No.: 851,567  ABSTRACT This invention relates to cameras for visualization of 52 us. 01 ..250/71.5 s 250/77 250/83 3 R internal organs and their Path1gY by means 5 1 isotopes. The new devices are characterized by the  Int Cl U Go 1/20 novel combination of an image intensifying tube with  Field of Search 83 3 77 a television pick-up tube and with means for rejecting 80 i 5 6 the scattered gamma radiation. In addition the new cameras are provided with novel luminescent screens  References Cited which are constructed of light conducting members of a tapered shape and phosphors mounted along the UNITED STATES PATENTS sidewalls of said members.
3,303,374 3/1967 Fyler ..250/80 13 Claims, 17 Drawing Figures PULSE 27 a; 5 75 e8 28 g l c/pcu/r 1 g am /0c E U 2/ ours/a4 L cou urek RA -/$ar0/=E f5 SOURCE RADIO-ISOTOPE CAMERAS USING VACUUM TUBES WITH FIBEROPTIC ENDWALLS AND LUMINISCENT MEANS OF FIBEROP'IIC CONSTRUCTION This invention relates to Gamma Cameras which are also known as Radio-Isotope Cameras and has a common subject matter with copending U.S. 3,499,017 filed Apr. 15, 1966 and issued Mar. 3, I970. The aforesaid 3,499,107 was a division of U.S. 3,279,460 filed Dec. 4, 1961 and issued Oct. 18, 1966, which was a copending division of U.S.3,02l,834 filed Nov. 28, 1956, which has a common subject matter and was copending with U.S. 2,877,368 filed Mar. 11, 1954. These devices serve to produce visible images or patterns of the distribution of gamma rays or other invisible radiations emitting isotopes in the examined parts. Their primary use is in the medicine for diagnosis of malignant tumors in internal organs such as brain, liver, kidneys or pancreas. They are also useful in nondestructive testing in industry.
The present devices of this type suffer from lack of sensitivity which requires that the time of exposure to produce one picture may be as long as -30 minutes. Such long exposures cannot produce satisfactory images because patients obviously must breath and move during such long periods of time. In addition such long exposures made impossible the study of short events occuring in the human body which are known also as dynamic studies of body processes. The above shortcomings of the present art are greatly improved by the novel devices to be described below.
It is therefore the purpose of the present invention to produce a Radio-lsotope Camera which has a much greater sensitivity than the standard devices.
Another purpose of this invention is to produce a Radio-Isotope Camera suitable for dynamic studies.
Another purpose of this invention is to make a device which will produce images formed by radio-isotopes of a better definition and contrast than the present devices.
The novel devices are illustrated in the drawings as follows:
FIG. 1 represents the novel Radio-Isotope Camera system.
FIG. 1A to 1D represent modifications of the first imaging tube in the camera system.
FIG. 2 represents a modification of the first tube which has a thin input endwall.
FIG. 2A represents a modification of the image tube with a thin endwall.
FIG. 3 represents a tube with electron multiplier plate.
FIG. 4 represents a novel luminescent screen using light conducting fibers for the Radio-Isotope Camera.
FIG. 4A-4F represent modifications of the novel luminescent screens using light conducting fibers.
FIG. 4G represents a novel X-ray Cassette.
FIG. 1 shows the Radio-Isotope Camera system 1. The radio-isotope image of the examined organ such as brain, or liver or kidney or pancreas is produced by the emission of gamma rays. Radio-Isotope compound is selectively localized in the tumor or other pathological area 30 in the brain 31 or other organ of the body. The emitted gamma rays get out of the skull, are collimated and focused by the collimating device 32. The collimated gamma rays beam impinges on the luminescent screen 3 or its modifications and is converted therein into an extremely weak luminescent image. The luminescent image is next transported to the photocathode 7 of vacuum tube 2 and is converted into a beam of photoelectrons having the pattern of said radio-isotope emission. The Camera 1 comprises a plurality of image tubes 2, 2a and 2b mounted in a tandem together. The luminescent screen 3 may be mounted on the outside of the input endwall 5 or may be mounted inside of the tube 2.
The input endwall 5 of the vacuum tube may comprise a fiberoptic part 6 which comprises a plurality of light conducting fibers of a transparent material of a high index of refraction, each of said fibers having an external part such as a coating of a material of a lower index of refraction than said fibers, which is described in detail in my U.S. Pat. Nos. 2,877,368 and 3,021,834. The input endwall 5 may be also of a standard type of glass endwall in which case the luminescent screen 3 is mounted outside of the tube 2 in a spaced relationship to said tube with an optical system disposed between them in order to focus the luminescent image from the screen 3 onto the photocathode 7.
In another modification shown in FIG. 2 the input endwall 6a is made of a standard glass construction as distinguished from the fiberoptic construction described above but has a novel construction in which the central portion 6b of said endwall is thinned out. This permits mounting of the luminescent screen 3 on the external surface of the endwall 6a of the tube 2 or its modifications without losing the resolution of the luminescent image which is unavoidable when the standard glass endwall is used. It is well known in the art that a thin endwall of the thinness necessary to preserve the resolution of an image in such device is not sufficient to support the atmospheric pressure. It was found however that if the luminescent screen is of a single crystal or if a mosaic of luminescent crystals is united together with a strong binder such as silicones or polycarbonates, the combined strength of such luminescent screen 3 and of the very thin endwall 6b is sufficient to withstand the atmospheric pressure.
Also the novel fiberoptic luminescent screens 50, 63, and can be used with a thin endwall 6b and will prevent the breakdown of said endwall. This construction is shown in FIG. 2A.
The input endwall 6 or 6a may be of a similar diameter as the rest of the tube 2 or may be many times larger as it is shown in FIG. 1A. This construction permits the use of a large luminescent screen, which in medical applications must be of diameter 6-9 inches, without the use of optical intervening means. The large size photoelectron image produced by the photocathode 7 may be demagnified electron-optically in the tube 2 so that the remaining part of the tube 2 and other vacuum tubes in the camera system 1 may be of a small size. It should be understood that electron-optical demagnification may be used for all vacuum tubes described.
The vacuum tube 2 has a photoemissive photocathode 7 supported by endwall or the aluminum disc 23 or by mesh screen 24, as explained. The photocathode 7 may be of any photoemissive material but it was found that the best results are obtained with a photocathode of K-Cs-Sb, because it produces less dark current than other photocathodes such as of K- Na-CsnSb type.
The vacuum tube 2 is provided with a luminescent screen 10 mounted on the inner surface of the opposite endwall 11. The screen 10 is provided with a light reflecting and opaque layer 10a such as of aluminum which is thin enough to be transparent to electrons. The endwall 11 comprises a portion 12 made of light conducting members of the same type as described above for the part 6 of the endwall 5. The construction of luminescent screen mounted on the array of light conducting members is described in detail in my U.S. Pat. No. 3,021,834.
The vacuum tube 2 and its modifications is provided also with focusing means 13 and electron accelerating means which are both connected to an outside source of electrical potential.
The luminescent screen 3 and its modifications may be also mounted within the tube 2 and its modifications. If it is inside the vacuum tube 2 it may be mounted on the inner surface of said input endwall for the support, as it is shown in FIG. 1B. In this embodiment the endwall 6c may be of a standard glass construction. The luminescent screen is provided with a light reflecting layer 3a. A light transparent separating layer 70 is provided to prevent chemical interaction between the photocathode 7 and screen 3. The layer 7a may be of A1 silicon oxide or of heat resistant plastics such as polycarbonates, sulphones or polyamides.
The screen 3 may be also mounted in the tube 2 and its modifications in a spaced relationship to the endwall. In such case it needs a support which may be in the form of an aluminum disc 23 as shown in FIG. 1C or may be supported by an embedding layer of light transparent plastic such as of polyesters, polycarbonates, sulphones or polyamides.
In some cases the luminescent screen 3 and its modifications may be supported by a light transparent plastic layer of one of aforesaid materials which is mounted on a supporting mesh screen 24 as shown in FIG. 1D. The luminescent screen 3 and its modifications may have a planar or a curved configuration.
The tubes 2a and 2b have a similar construction as the tube 2, except that they are provided with a higher electrical potential than the tube 2 for further acceleration of electrons and intensification of the final luminescent image. The tubes 2, 2a and 2b are mounted with their fiberoptic endwalls in contact with each other. The combined intensifying action of said plurality of tubes produces the fluorescent image on the final luminescent screen in tube 2b which is 50,000 times brighter than the original luminescent image in the screen 3.
In some cases the vacuum tubes 2or 2a or 2b and their modifications may be further provided with image intensifying plate 36 of electron multiplying channelled type, as it is shown in FIG. 3.
It should be added that in some applications the construction of this part of camera I may be modified so that instead of using 3 or more vacuum tubes 2, 2a and 2b as described above, a single vacuum tube is used. Such vacuum tube must be provided with a few intensifying composite screens as it is described in my U.S.
I Pat. No. 2,555,423 and others.
The patient receives the necessary dose of radio isotope which emits gamma rays or other invisible radiations. The radio-isotope is incorporated a vehicle which will localize preferentially in the part of the body which has to be investigated for example Technetium compounds containing "Tc localize well in the brain, whereas Selenium compounds containing "'Se are useful for pancreas and iodine compounds for thyroids. The amount of radio-isotope given to the patient has to be very small because of patients safety. As a result of this limitation the exposure to produce one image in the devices used at present has to last 5-30 minutes. This as it was explained above causes inavoidable motion and breathing defects in the final image. The present device produces simultaneous amplification of the entire image by the factor of 50,000 which allows to reduce the time of exposure and obtain pictures of much better resolution.
Another serious problem in producing the images of the organs of the body by means of radio-isotopes is the. presence of scattered gamma radiation which being superimposed on the imaging gamma radiation acts as fog and destroys detail and contrast of images. The means for removing at least a part of this fog are known as pulse amplitude or height discriminating circuits. They are however truly effective only in the gamma cameras of mechanical type in which the image is produced not simultaneously but sequentially point after point and which results necessarily in extremely long exposure as it was explained above. The novel system to accomplish the elimination of scattered radiation and permit at the same time short exposures is shown in FIG. 1 and uses a novel combination of amplifying image tubes 2-2a-2b with a television pick-up tube of image dissector type 15 and with pulse amplitude discriminating circuits 25. The vacuum tube 15 is provided with the photocathode 17 of photoemissive type mounted on the endwall 16. The endwall 16 should be made of light conducting members or comprising a part made of such light conducting members as it was described above for endwall 6 and its modifications. In some applications the endwall 16 may be of standard type but in such case an optical system must be interposed between the last image tube 2b and image dissector type 15 which causes a great loss of light. The vacuum tube 15 is provided with a diaphragm 18 which has an aperture 18a which serves for the passage of electrons from the photocathode 17. In addition vacuum tube 15 has electron focusing means and deflecting means 19 which may be of magnetic type or electrostatic type. The deflecting means serve to scan the photoelectron beam from the photocathode 17 against the aperture 18a permitting the passage of only one image point at a given time. The transmitted electrons of each image point impinge sequentially on the secondary electron multiplier 20 of a multistage type. The multiplied secondary electrons are collected by the anode 21 and are converted into video signals over a suitable resistance as it is well known in the television art. Video signals-corresponding to one image point at the time are fed into pulse amplitude discriminating circuits 25. The circuits 25 serve to pass only video signals of a predetermined high amplitude and to reject pulses of a lower amplitude. In this way video signals produced by the original imaging gamma radiation will be passed but video signals produced by scattered radiation being of a lower ener gy than the original imaging radiation will be rejected. It may be repeated that the scattered gamma radiation corresponds to a photographic fog in the sense that it does not contribute to the image but degrades and obscures the image. The original energy of gamma rays emitted by Neohydrine which is a radio-isotope of Hg and is useful for diagnosis of brain tumors is about 289 KV. The scattered gamma radiation produced by the collision of original gamma rays with brain tissues have a spectrum of different energies but all of them are below 289 KV and therefore can be eliminated by the use of the circuits 25. In the same manner "Technetium compounds which are also useful for brain tumor localization emits peak energy gamma rays of I50 KV whereas scattered gamma rays are of a lower energy.
There are many types of pulse amplitude discriminating or analyzing circuits which are well known in the art. Some of them are known as integral discriminators and are described in detail in Chase, R.L., Nuclear Pulse Spectrometry, McGraw-I-Iill, New York, 1961; Schmitt, 0., A Thermionic trigger. J. Sci. Instr. 15, 24 (1938). Other more complicated types are known as Differential Amplitude Analyzers. Some of them are designed especially for stability and are described in detail in Kandiah, K., A sensitive pulse amplitude discriminator. Proc. Inst. Elec. Engrs. (London) Pt. II 101, No. 81, 239 (1954); Orvis, A. L., Koenig, M. P., and Owen, C. A., Jr., In-vivo measurement of thyroidal radioiodine: effect of neck scatter. J. Clin. Endocrinol. Metab. 17, 966 (1957). Even more advanced types are known as Multichannel Analyzers and serve for conversion of analog data into digital data, as it is described in Scientific Literature. This technique is further developed by using means for storage of digital data as described in Hutchinson, G. W., and Scarrott, C. G., A high precision pulse height analyzer of moderately high speed, Phil. Mag. 42, 792 (1951). A thorough review of various Discriminating Circuits is given in McCollom, K. E., Discriminators, Nucleonics 17, No. 6, 72 (1959). It should be understood that all types of above described pulse amplitude analyzing and discriminating circuits and analog to digital conversion circuits may be used in my camera system 1.
In addition the camera 1 may use all image contrast in detail enhancing means such as image density tracers or quantizers.
The use of pulse amplitude discriminating circuits 25 is well known in the art but none of the previous devices could use them and produce the results which are possible only with the novel camera 1.
The novel Radio-Isotope Camera 1 is free from limitations of the present devices in which the spatial resolution is inherently related to the energy resolution of the device excluding thereby the use of radioisotopes of a low energy. The novel Radio-Isotope Camera 1 is free from limitations in the spatial resolu tion of other camera devices which impaires the definition of the final image to be diagnosed.
The novel Camera permits also making pictures of examined organs in a few seconds time due to its much greater sensitivity.
The signals which passed Pulse Amplitude Discriminating Circuits may be fed into display devices such as a kinescope 26 or an array of luminescent diodes. The signals may be also fed into various storage devices and/or in computers. The signals may be also fed into various data processing devices such as scalers, decimal registers, ratemeters, etc. It should be understood that all means for display or for storage or for counting or for other utilization of signals may be used in the Camera 1. The kinescope 26 may produce a luminescent image on its luminescent screen 27, which may be photographed by a photographic camera 28. The kinescope 26 may be provided with a fiberoptic endwall, as it is described in my U.S. Pat. No. 3,021,834.
The Camera 1 may also produce multi-color images using various multi-color display means which are known in the art.
One of the greatest problems in the present Radiolsotope Cameras is the basic conflict between the sensitivity of said cameras and resolution of images. A good sensitivity of a camera requires a very thick luminescent screen which will be capable of absorption of penetrating gamma rays such as KV gammas of Technetium or 289 KV of Hg or 364 KV of l. At the same time the thicker is the luminescent screen the worse is the resolution of images produced by a gamma camera. It follows that these two requirements are diametrically opposed to each other. This basic problem was solved by the novel luminescent screens which use phosphors in combination with light conducting members and which are described in detail below.
FIG. 4 shows the construction of one of such luminescent screens 50. The screen 50 is constructed of a plurality of light conducting members 51 which are described in my U.S. Pat. No. 2,877,368 filed Mar. 11, 1954 and in U.S. Pat. No. 3,021,834 filed November 1956 as follows:
The image conductor 51 consists of multiple fibers of material having a high refractive index such as quartz, rutile or special plastics. In many applications the image conductor must be flexible and easily malleable. In such cases acrylic plastics such as Lucite or polystyrenes may be used. Especially Lucite is suitable for this purpose because it causes smaller losses of conducted light than other materials. Lucite and other above mentioned materials characterized by a high refractive index have the property of internal reflection of the light conducted by them. Such materials cannot conduct a whole image as such but they can conduct well a light signal, it means an image point. The size of the image point I found is determined by the diameter of a single conducting fiber 52. In my image conductor 1 assembled a bundle of such fibers which form a mosaic-like end-faces and which therefore can conduct plurality of image points. All these image points will reproduce at the other end-face of the image conductor the original image provided that the image conducting fibers remain in their original spatial relationship. Each fiber 52 should have, as was explained above, a diameter corresponding to the size of one image point. The
diameter of 0.1 millimeter is well suitable for the purposes of my invention. In order to conduct an image of an area, e.g., of 1 square centimeter we must have many fibers 52, the number of fibers being dependent on the resolution of reproduced image that we desire. If the resolution of the conducted image should be 4 lines per millimeter, and if the image is of one square centimeter in size, we will need 40 fibers of 0.25 millimeter in diameter. As in many examinations it is not practical to be limited to the field of l cm?, I preferably use a few hundred of such fibers combined in one image conductor, which will allow to transmit an image of a large area.
The light conducting fibers should be polished on their external surface very exactly. They may be also preferably coated with a very thin light opaque layer which should have a lower index of refraction than the light conducting fiber itself. Such coating may have a thickness of only a few microns. I found a great improvement of flexibility of the light conductor 51 can be obtained by having the light conducting fibers 52 glued together only at their end-faces 51a and 51b. This is a very important feature of my device because the main requirement from the light conductor 51 is its flexibility and malleability. If the fibers 52 are glued together along their entire length the flexibility and malleability is so much reduced that it may be not possible to use it in many examinations in which the walls or passages are fragile and may be damaged by a rigid instrument. I found unexpectedly that having the conducting fibers 52 free along their path between the end-faces will not cause any deterioration of the conducted image. I found that in spite of the fact that fibers between their end surfaces were freely movable there was no blurring of the conducted image. It must be understood, however, that the fibers 52 at both end-faces of the conductor 51 must rigidly maintain their spatial relationship. Another important feature of this construction is that the diameter of the light conductor 51 can be now increased because no space consuming binder or glue is present between the fibers 52 except at their end-faces. Instead of using the binder at the end-faces of fibers 52, they may also be held together at their end-faces by a fine mesh screen. Each fiber is threaded through one opening of said mesh screen and is being held by said screen in constant position.
It may be added that smaller losses of light may be obtained if the fibers 52 are hollow inside instead of being solid.
The difference between the light conducting members 51 of the present devices and the light conducting members in the aforesaid parent patents resides in a tapered which means conical construction of the light conducting members 51. The core part or the internal part 52 of the members 51 is of a transparent material of a high index of refraction such as quartz, rutile, glass or plastics as described above. The external part or the coating part 53 is of material of a lower index of refraction than the part 52. The luminescent material 54 is mounted on the sidewalls or adjacent to the sidewalls of the light conducting members 51. The luminescent material 54 may be of many phosphors which are reactive to electromagnetic radiations or to atomic particles. Suitable phosphors are Nal (Tl), CsI, CaWO Ba(Pb)SO anthracene, uranyl compounds and others. In some cases luminescent glasses containing rare metals such as terbium, holmium or dysprosium or their compounds may be used also. One light conducting member 51 with the luminescent layers 54a and 54b represents one image point of the examined part of the body. The length of the members 51 was found to have no effect on resolution and on the size of an image point. This novel feature permits the use of a phosphor layer 54a and 54b of a great length which means of a great thickness without any damage to resolution of images. It may be recalled that in the present luminescent screens their thickness has to be very small because the resolution of two-dimensional images produced by such screens is limited to the thickness of the luminescent layer itself. It may be repeated that the radio-isotopes emit very energetic rays such as of ISOKV-SOOKV energy. Such gamma rays cannot be absorbed by the conventional luminescent screens because a luminescent layer of the thickness between 1 inch and 4 inch is required for this purpose. Such thickness will produce an image point of 1-5 inch size which is obviously useless for producing any images. On the other hand the novel luminescent screen 50 or its modifications to be described below can use luminescent layers 54a and 54b of the thickness 1-4 inch without impairing resolution of image.
In addition it was found that the novel screen 50 or its modifications can produce such results not only when using phosphors transparent to their luminescent emission such as Nal(Tl) or CaWO but unexpectedly they may also use layers of phosphors such as Csl, Ba(Pb)SO or ZnSCdS which are nontransparent. In distinction to the standard screens in which such nontransparent luminescent layers are limited to the thickness of a fraction of one millimeter, as the luminescent radiation cannot escape from them otherwise, the novel screens can use such layers in the thickness of many inches.
The use of very thick layers of phosphors was made possible by the novel device in which the luminescent layers are combined with the light conducting members 51 which are provided with a conical configuration. The luminescent light from phosphor 54a and 54b enters the'members 51 through their sidewalls and is trapped and transported along said members by internal reflection mechanism until it exits through the output endface 51a.
If transparent phosphors are used the light conducting members 51 should be separated from each other by light opaque means 56 to prevent an optical crosstalk between adjacent light conducting members. In some case light opaque means 56 may be used only between every second light conducting member 51. If the phosphors used are of non-transparent type, the light opaque means 56 may be omitted.
It was found that the greater is the tapering of the light conducting fibers 51, the better is their efficiency of the light transfer.
Further increase in sensitivity of luminescent screen 50 and its modifications may be obtained by applying an additional phosphor layer 58 to the input endfaces 51b of the members 51 or to the entire input side of the screen 50, as it is shown in FIG. 4A.
The light conducting members 51 carrying the luminescent layers on their sidewalls are united by binders of organic type such as silicones or of inorganic type such as solder glasses, potassium silicates or ceramics. In some applications instead of using the binders, the endfaces of light conducting fibers 51 are preferably held together at their endfaces by a mesh screen 60 and 61 as it is shown in FIG. 4B which illustrates the novel luminescent screen 63. Light conducting fibers 51 are threaded through openings 62 and 62a of said mesh screens 60 and 61 and are held by said screens in constant position.
The luminescent material 54 may be injected in a liquid form or insufflated in a powder form or deposited in a crystal form into the space between the sidewalls of the adjacent two light conducting members 51. The openings 62a of the mesh screen 61 may be occluded by the distal ends of the light conducting members 51. In some cases an additional light transparent very thin layer may be deposited across the screen 61 to prevent the loss of luminescent material.
Instead of two mesh screens 60 and 61 a perforated plate 65 of a metal or of an opaque material such as plastic may be used to form a luminescent screen 68 as shown in FIG. 4C. The plate 65 has straight or tapered channels 66 extending across the entire thickness of said plate which can accomodate and hold the light conducting members 51 and in addition provide open spaces 67 on each side of said members 51 for depositing luminescent material 54a therein. The luminescent material 54a may be injected in liquid form such as a solution of NaI(Tl) or in a powdered form or in a crystal form as it was explained above.
Another modification of this invention is shown in FIG. 4D, which shows a perforated honey-comb 40 used instead of a perforated plate 65 described above. It was found that honeycomb 40 permits easy construction of long channels 41 which are necessary for luminescent layers. The honey-comb support for light conducting members 51 may have channels 41 of tapered configuration or of parallel configuration. The channels 41 may be open at both ends or may be closed at one or both ends. The sidewalls of honeycomb are preferably light opaque'and light reflecting. A great advantage of this novel construction resides in the facility of depositing luminescent material in the necessary thickness on sidewalls of each of plurality of light conducting members 51 and represents therefore an important feature of this invention.
Another embodiment of this invention is shown in FIG. 4E which illustrates the luminescent screen 70. In this embodiment the conical light conducting members 51 are leached out to provide empty spaces 71 or even passages therein forming thereby hollow light conducting members 51A. The empty spaces 71 may extend through the entire length of members 51A or may terminate before their endfaces 51a. The hollow spaces 71 should not extend laterally to the external part of the light conducting members which is of a lower index of refraction 53 but should be confined by the residual wall of material of high index of refraction 52. In this embodiment light opaque means should be provided between the two adjacent members 51A or at least between the pairs of two adjacent members 51A to prevent optical cross-talk by luminescent radiation escaping through sidewalls of said members 51A.
FIG. 4F illustrates another modification showing the luminescent screen 80 in which light conducting members 51A are mounted in a metal or plastic plate 82 which has straight or tapered passages for accepting the conical and hollow light conducting members 51A and for providing spaces 71 for deposition of the luminescent material 54, as it was described above and shown in FIG. 4E.
Instead of a perforated plate 82, mesh screens 61 and 62 can be used at the ends of light conducting members 51A, as it was described above and illustrated in FIG. 4D.
It should be understood that each of the opposite ends of the conical light conducting members may be mounted inside the mesh screens or 61 or perforated plate 65 or perforated honeycomb or crate-like supporting member or may be mounted flush with the openings of said mesh screens 60 or 61 or with openings of said plate 65 or of said honey-comb or may be mounted outside of said openings of said mesh screens or of said plate or of said honeycomb supporting member.
It should be understood that each of luminescent screens described may have an additional layer of luminescent material deposited on its input endface as it is shown in FIG. 4A for layer 58.
It should be understood that in all luminescent screens described the input endface 51b of light conducting members 51 or 51A or their modifications may be made larger than the output endface 51a of said members. It was found however that in this construction a much larger percentage of luminescent light escapes through the sidewalls of light conducting members.
It should be understood that each of luminescent screens described may be mounted in a spaced relationship to the vacuum tube 2 or its modifications or may be mounted in contact with the input endwall 6 or its modifications. In some cases it is preferably to use the luminescent screens described herein as part of the input endwall 6 or its modifications of the vacuum tube 2 or its modifications. This construction was found to improve the sensitivity of the camera. In this embodiment an additional light transparent layer of glass 'or potassium silicate may be added to the end-face of the luminescent screen to improve vacuum-tightness of said insert.
It should be understood that each of novel luminescent screens described may be mounted inside the vacuum tube 2. In such case the photocathode 7 of tube 2 is mounted on the outside endfaces 51a of said luminescent screen and may be in contact with said endface or may be separated from said endface by A10 or of silicon oxide or of light transparent heat resistant plastics such as described above. It should be understood that all modifications of the mounting and supporting of the luminescent screen 3 described above apply as well to the novel luminescent screens 50, 63, or and their modifications.
It should be understood that all novel luminescent screens 50, 63, 70 and 80 and their modifications may be used also for X-ray Image Intensifiers and Neutron Image Intensifiers. If the X-ray Image Intensifiers are used for medical diagnosis in which the energy of X- rays does not exceed -140 KV, the phosphor layers 54a and 54b may be of a smaller length than in Radio- Isotope Cameras. The embodiment of such X-ray or neutron image intensifier shown in FIG. 4F; in which the novel fiberoptic luminescent screens serve in addition as a support for the photocathode 7.
In the use in neutron image intensifiers, the phosphor layers 54a and 54b may be enriched with materials which capture neutrons such as boron, indium, cadmium, gadolinium or hydrogenous compounds such as paraffin. The neutron captivating materials may be also provided in the form of a separate layer adjacent to the phosphor layers 54a and 54b.
It should be understood that the novel luminescent screens alone or together with image intensifiers described above can be used for producing neutron images by a transfer technique which is described in the book titled Neutron Radiography by H. Berger.
It should be understood that all novel luminescent screens 50, 63, 70, 80 or their modifications may be used with all vacuum tubes described above instead of the luminescent screen 3 or in addition to said luminescent screen 3.
It should be understood that in some cases the light conducting members 51 may have parallel sidewalls or other configuration instead of the tapered shape described above and that such construction applies to all embodiments of invention.
In conclusion it was found that in many radio-isotope examinations, the use of novel luminescent screens described above was essential for the operation of the entire imaging camera devices.
In addition it should be understood that all vacuum tubes described above may be provided'with image intensifying plates 36 of channelled electron multiplier type, shown in FIG. 3.
It should be understood that all novel luminescent screens and their modifications may be used in some applications with an array of solid-state photosensors instead of using vacuum tubes described above. The photosensors may be photo-cells such as of CdS or photo-diodes especially of avalanche type, p-i-n detectors or phototransistors.
It should be understood that all the novel luminescent screens described herein and their modifications may be used in X-ray Cassettes as image intensifying screens instead of standard intensifying screens as it is shown in FIG. 46.
All novel luminescent screens can be also used in combination with solid state intensifiers such as panels comprising photoconductive layers and electroluminescent layers, described e.g. in the book Optoelectronic Devices" by Weber.
As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiments above set forth, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
What I claim is:
1. A camera for examination of internal parts of the body formed by radio-isotopes emitting an invisible radiation comprising in combination luminescent means producing a first luminescent light pattern, vacuum tube means provided with a photoelectric screen mounted within said tube, said vacuum tube means converting said first pattern into a second luminescent pattern, a television pick-up tube for receiving said second luminescent pattern and converting said second pattern into an electron beam, a scanning aperture mounted in the path of said electron beam and means for deflecting said electron beam across said aperture, and means converting the electrons of said beam transmitted through said aperture into successive electrical signals, said device comprising furthermore means for receiving said signals and discriminating said signals whereby only signals of a predetermined amplitude are passed ,and means for receiving said passed signals and utilizing said signals.
2. A device as defined in claim 1, in which said television tube is provided with an endwall having at least a part constituted of a plurality of light conducting members comprising a core of a transparent material of a high index of refraction, and a peripheral part of material of a lower index of refraction than said core, said members conducting light by internal reflection.
3. A device as defined in claim 1, in which said luminescent means comprise a plurality of light conducting members and a luminescent material mounted along the sidewalls of said light conducting members I and outside of said light conducting members, and in which the longitudinal dimension of said luminescent material if greater than the transverse dimension, in which device furthermore said members conducting light by internal reflection.
4. A device as defined in claim 3, in which said light conducting members have an internal part of a transparent material of a high index of refraction and an external part of material of a lower index of refraction than said internal part.
5. A device as defined in claim 3, in which said light conducting members and said luminescent means are mounted in channels of a supporting member.
6. A device comprising in combination a luminescent array comprising a plurality of light conducting members comprising a light transparent material and phosphor means mounted along the sidewalls of said light conducting members and emitting luminescent light in response to an invisible radiation, said phosphor means having the longitudinal dimension greater than their transverse dimension, and means for receiving and utilizing said luminescent light.
7. A device as defined in claim 6, in which said light conducting members have a conical shape.
8. A device as defined in claim 6, in which the external part of said light conducting members comprises material of a lower index of refraction than the internal part of said light conducting members, and in which device said members conduct said luminescent light by internal reflection.
9. A device as defined in claim 8 in which said phosphor means are supported by said sidewalls.
10. A device as defined in claim 9 in which said light conducting members are united together and in which said receiving means comprise a vacuum tube.
11. A device as defined in claim 8 in which light opaque means are mounted between said phosphor means.
12. A device as defined in claim 7 in which said light conducting members are united together to form a screen.
13. A device as defined in claim 7 in which light opaque means are mounted between said phosphor means, and in which the external part of said members comprises material of a lower index of refraction than the internal part of said members.