US2885559A - Method of operating x-ray device - Google Patents

Method of operating x-ray device Download PDF

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Publication number
US2885559A
US2885559A US645695A US64569557A US2885559A US 2885559 A US2885559 A US 2885559A US 645695 A US645695 A US 645695A US 64569557 A US64569557 A US 64569557A US 2885559 A US2885559 A US 2885559A
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Prior art keywords
screen
ray
rays
luminous
irradiation
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US645695A
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English (en)
Inventor
Destriau Georges
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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Priority to US645695A priority Critical patent/US2885559A/en
Priority to JP642758A priority patent/JPS364477B1/ja
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/64—Circuit arrangements for X-ray apparatus incorporating image intensifiers

Definitions

  • This invention relates to X-ray-electroluminescent devices and, more particularly, to a method for operating a liuoroscopic system.
  • the images are produced by irradiating a phosphor screen with an X-ray signal.
  • the brightness of the image which results normally varies according to the intensity of the X-rays striking the iluoroscopic screen. It is desirable to achieve as bright a picture as possible without exposing the object being X-rayed to excessive irradiation, particularly where living organisms are concerned.
  • the aforesaid objects of the invention, and other objects which will become apparent as the description proceeds,- are achieved by providing a process for operating an X-ray apparatus incorporating an X-ray-responsive phosphor screen characterized by displaying an enhanced luminous output when excited by X-rays and simultaneously placed within the influence of an alternating electric field.
  • the phosphor screen is presensitized by applying thereto X-ray irradiation which preferably is of substantially uniform intensity. Simultaneous with the X-ray irradiation an electric field is applied across the screen and the X-ray irradiation and electric field are then removed.
  • the screen is irradiated with the X-ray signal which is to be reproduced on the screen and the resulting image will have enhanced brightness, or enhanced brightness with a varied contrast, depending upon the quantity and intensity of the X-ray irradiation to which the screen is exposed.
  • Fig. l is a sectional elevation of the preferred X-rayelectroluminescent fluoroscopic screen
  • Fig. 2 is a schematic diagram of the X-ray unit and operating circuit therefor, illustrating the phosphor screenpresensitizing operation
  • Fig. 3 is a schematic diagram similar to Fig. 2 illusltrating the second phase of the equipment operation
  • Fig. 4 is a graph of the ratio of enhanced output vs. X-ray irradiation of a presensitized uoroscopic screen
  • Fig. 5 is a graph of brightness in arbitrary units vs. time, illustrating the operation of the unit so that the screen luminesces with a very bright picture and with an enhanced contrast;
  • Fig. 6 is a graph similar to Fig. 5, but illustrating the operation of the system so that the image produced has an enhanced brightness and the same contrast as would be obtained for a normal liuoroscopic screen;
  • Fig. 7 is a view similar to Figs. 5 and 6, but showing the operation of the unit so that the image produced has a contrast which is decreased over that which would normally be obtained when irradiating the usual uoroscopic screen.
  • the phosphor materials which may be used in this co-pending application are those which will display an enhanced luminous output when excited by X-rays and simultaneously placed within the influence of an alternating electric field. This is contrary to the action of most phosphors which will display a quenching eiect under similar conditions.
  • the phosphors which may be used in the instant system are those which may be used in the so-called X-ray enhancemen as disclosed in the heretofore-mentioned copending Destriau application, namely, those phosphors which display an enhanced output when irradiated with X-rays and simultaneously placed within the inlluence of an alternating electric iield.
  • Speciiic phosphors which will be suitable for the instant purpose are mixtures of zinc sulde and cadmium sulfide wherein the molar ratio of zinc to cadmium is from nine mole parts zinc, one mole part cadmium to three mole parts zinc, seven mole parts cadmium and activated by from 0.01 102 to 6.O 1()*2 mole of manganese per mole of luminescent material.
  • the phosphor material may be-activated by a mixture of manganese and silver, with the silver being present in amounts of from traces (O.00l 102 mole silver per mole manganese) up to about 1.0 l02 mole silver per mole manganese.
  • zinc-sulfide phosphors which are activated with manganese or mixtures of manganese and silver in the heretofore-disclosed amounts are also suitable.
  • the phosphor material may comprise 1CdS'3.5ZnS, activated by 1X l0-4I mole manganese per mole of ⁇ luminescent material, such a phosphor having been fired during preparation at a temperature of from 800 C. to 1150 C.
  • Fig. 1 is illustrated the preferred embodiment of the electroluminescent-lluoroscopic screen 10 which comprises a substantially planar layer of luminescent material 12 adjacent a vsubstantially planar layer of dielect tric material 14 with the luminescent and dielectric material's being sandwiched between two thin, conducting layers or 'electrodes 16 and 18.
  • Each 'of the lelectrode layers 16 and 18 may be connected through suitable bus bars 20 and suitable electrical connection 22 to the ⁇ electroluminescent field-voltage supply described hereinafter.
  • a foundation-viewing plate 24 is placed over one of the conducting layers, for example electrode layer 18 and an insulatingdayer 26 may be placed over the ⁇ other conducting electrode layer 16 in order to minimize 'shock hazard.
  • a protecting and handling shield 28 may be provided around the entire periphery of the screen in order to facilitate storage, handling, etc.
  • the luminescent material layer 12 is preferably positioned next to the foundation-viewing plate 24, although Ifor 'some applications it may be preferable to place the dielectric layer 14 next to the viewing Aplate 24.
  • the thickness of the luminescent material layer 12 is not particularly critical, but as a specific example, it may have a thickness of 0.2 mm.
  • the dielectric layer 14 may comprise any suitable dielectric which has a high dielectric constant, is transmissive to either visible light or to X-rays depending upon its position within the screen, and will not deteriorate rapidly under the action 'of ⁇ X-rays. Such materials are well known and as an example, the dielectric material layer 14 may comprise 'a mica sheet about 0.05 mm. thick, although this thickness is in no way critical and may be increased or decreased as indicated by the application.
  • a suitable light-transmissive dielectric material such as polyvinyl-chloride acetate may be admixed with the phosphor and the separate layer of dielectric dispensed with, if desired, or the dielectric material may be dispensed with entirely in some special applications and only the phosphor layer 12 placed between the electrodes 16 and 18. It should be pointed out that the purpose of the dielectric material is to prevent electrical breakdown through the phosphor and between 'the electrodes 16 and 18 and the electric elds as may be used herein need not be particularly intense.
  • the usable electric iields may vary over a wide range as in the heretofore-mentioned copending De'striau application and as a specific example, the electric eld which is applied across the screen during screen presensitization may have an intensity of 20 kv. per cm.
  • the conducting electrodes 16 and 18 may be fabricated of any conducting materials which may be coated as a thin sheet and are transmissive to visible light in the case of the lower layer 18 and transmissive to X- rays in the case of the upper layer 16. Of course, these electrodes should not deteriorate appreciably under the action of X-rays.
  • the electrode 18 may be fabricated of a thin layer of tin oxide on a glass base, such as sold under the trademark Nesa by Pittsburgh ⁇ P1ate Glass Co., Pittsburgh, Pa.
  • Other suitable thin conducting coatings such as oxides of zinc, cadmium, aluminum or bismuth, for example, may also be used.
  • the electrode 16 may be fabricated of tin oxide, for example, or it may be a thin coating of aluminum which may be applied by the well-'known vacuum-metalizing techniques.
  • the thin protective layer 26, which is intended to insure against shock hazard and to facilitate handling, may be fabricated of any X-ray transmissive material which has relatively good electrical insulation properties and plastics such as polytetrauoroethylene are suitable.
  • the protective layer 26 may be dispensed with, if desired, and the shock hazard eliminated by grounding the electrode 16.
  • the foundation glass-viewing plate is normally fabricated of any glass which contains heavy atoms which will absorb the X-rays and thus protect the viewer or .the photographic plate, as the case may be.
  • any of the well-known lead or cerium glass may he used.
  • the protecting and handling shield 28 maybe fabricated of a plastic similar to the layer 26 and this shield may be dispensed with, if desired.
  • Fig. 2 is illustrated, in block diagram, one embodiment of a suitable X-ray apparatus which in this showing is set for initial exposure of the object being X-rayed in order to presensitize the uoroscopic screen 10.
  • This apparatus 30 comprises an X-ray rectifier and transformer unit 32, X-ray and iilm shutter timer 34, X-ray tube 36, iield-voltage-control unit 38, field-timer unit 40, the X-ray fluoroscopic screen 10, exposure switch 42, electric-field switch 44, camera lm 46, camera-shutter tripping unit 48 and camera shutter 50.
  • Fig. 3 is shown in block diagram ⁇ the same X-jray apparatus as is shown in Fig. 2, but with the electric tield switch 44 in open position.
  • the apparatus With the X-ray iiuoroscopic screen presensitized, the apparatus is thus set to irradiate ⁇ the object being X-rayed with X-rays which preferably are relatively intense, in order to produce on the fluoroscopic screen a very bright and transient luminous image, as will be explained more fully herein after.
  • the details of the operation of this apparatus will be considered as the description proceeds.
  • the object 52 being X-rayed will be assumed to be comprised of two portions of different X-ray permeability.
  • screen presensitization it has been found that when a fluoroscopic screen of the type described herein is iradiated with X-rays of substantially uniform intensity and simultaneously placed within the influence of an alternating field, a portion of the luminous response developed by the screen-applied X-rays will be imparted to the screen and in effect stored This is termed screen presensitization. yThis screen-imparted X-ray irradiation may be released from the so-called presensitized screen by a second X-ray irradiation and the intensity of the stored X-ray irradiation which will be released is dependent upon the intensity of the second X-ray irradiation.
  • a signal 4 is thus generated by irradiating an object which has varying permeability to X-rays
  • the intensity of the X-ray irradiation striking the screen will vary according to the X-ray permeability of the object and the screenstored energy may thus be used to reproduce the image which corresponds to the X-ray signal. Presensitization is not effected by the field alone, nor will the field alone, as specified, develop an appreciable .pure electrolnrninescence.
  • Fig. 4 is shown a graph of enhancing ratio vs. second X-ray irradiation, expressed vas milliamperes of current drawn by the X-ray tube 36.
  • the screen 10 was presensitized ⁇ and the screen brightness was measured with no object between the screen and the X-ray tube when it drew the indicated currents.
  • inclusion of an X-ray absorptive object between the screen 10 and tube 36, after the screen has been presensitized, requires a greater intensity of X-ray irradiation to deliver to the screen 10 an equivalent intensity of X-rays.
  • the brightness ratio is also dependent upon the intensity of thev second X-ray irradiation of the screen, which in the instant method takes the form of an X-ray signal, and this is plotted as the abscissa in these curves.
  • Bm is the maximum brightness in arbitrary units for a presensitized screen and B is the maxi mum brightness in arbitrary units for an unsensitized screen irradiated with equal-intensity X-rays
  • the X-ray tube 36 as used herein had a hard glass window and was operated at a voltage of 80 kv. with a self-rectified circuit. The distance from the centerline of the tube to the screen 10 was 20 cm. Under these conditions of operation, the tube current and time were measured to the indicated values of Q (quantity of X-rays) and j (tube current). It should be understood that the foregoing example of operating conditions may be modified as indicated by the application. Also the quantity Q of presensitizing X-rays may be obtained by means of a more intense X-ray irradiation for a shorter time, for example.
  • Fig. 5 is illustrated the operation of the equipment in order to achieve a very bright signal without appreciably increasing the quantity of X-rays applied to the object being X-rayed and in addition, Fig. 5 illustrates the operation of the equipment in order to obtain a very high degree of contrast in the image produced on the screen.
  • the object 52 being X-rayed may comprise two portions, one portion of which has seven times the permeability ⁇ to X-rays as the other portion.
  • the screen is first presensitized by applying thereto an X-ray irradiation, which preferably has substantially uniform intensity, for a sufiicient period so that the quantity of X-rays striking the screen is 160 na. min.
  • An electric field is simultaneously applied across the screen with the X-ray irradiation and the field is preferably removed shortly after the X-ray irradiation in orderto avoid desensitizing the presensitized screen.
  • the brightness of the screen during the presensitization will follow the curve O-M-N and the field is preferably removed at point P which may be 10 seconds, for example, after the X ray irradiation is stopped.
  • point P may be 10 seconds, for example, after the X ray irradiation is stopped.
  • the object which is to be X-rayed is placed between the X-ray tube ,-36 and the screen 10 and relatively intense X-rays are applied to the object to generate an X-rayv signal which is applied to the screen.
  • the brightness of the screen will follow the curve O-R-S. Without the screen presensitization, the brightness of the screen would follow the dotted line04. At point S, the transient image, which represents the stored luminous energy, will be substantially expended.
  • the best brightness ratio which has been achieved in a released image is about 2.66:l while a brightness enhancement of from 4 to 5:1 and greater has been achieved where the field is simultaneously applied across the phosphor with the X-ray signal.
  • the build-up in luminosity-of the enhanced brightness where the field is simultaneously applied is relatively slow and accordingly, the quantity of X-rays required to produce such ultimate enhanced luminosity is correspondingly great.
  • the buildup in luminosity of the screen, upon application of the intense X-ray signal is quite rapid since the presensitizing energy is being released.
  • the X-ray signal irradiation of the screen may be stopped and the total quantity of the X-rays to which the object is exposed need only be relatively small in order to obtain a relatively bright image.
  • the switch 44 when the switch 44 is raised to an elevated position to open the field timer unit 40, it renders operative the camera-shutter-tripping unit 48.
  • the unit 34 When the exposure switch 42 is closed, the unit 34 is actuated and at a predetermined time thereafter, the shutter-tripping unit 48 actuates the film shutter 50 to record the brightest portions of the transient image.
  • the X-ray signal irradiation may be stopped and this may be effected by opening the exposure switch 42 -orby setting the timer unit 34.
  • the camera may record the image five seconds after the X-ray signal irradiation of the screen 10 is started.
  • Fig. 6 is illustrated the operation of the unit wherein the contrast in the image produced on the screen is maintained the same as what it would be with the usual operation of a fiuoroscopic screen.
  • the screen 10 is presensitized as previously explained,
  • the intensity of the X-ray striking the screen adjacent the more X-ray opaque portions of the object will have an intensity equivalent to f1-0,7 milliamp. and as shown in curve D, the ratio of Bn divided by B0 is still about 1.9.
  • the contrast between the brighter and darker portions of the screen will remain the same as that 'contrast which would be achieved with no screen presensitization.
  • the brightest portions of the transient image may be recorded photographic'ally as explained hereinbefore.
  • the screen brightness under the indicated X-ray signal irradiation would follow Vthe dotted curves in Fig. 6.
  • Fig. 7 is illustrated the operation of the -system whereby the contrast between individual portions of the image may be decreased.
  • the object 52 being X-rayed has been assumed to be comprised of two portions, one of which has seven times the permeability to X-rays as the other portion.
  • the screen is iirst presensitized to a total Q of 2O ya. min., see curve F in -Fig. 4.
  • the ratio of Bm divided by Bo will be 1.06-
  • the brightest and darkest portions of the image (points -U and U', Fig. 7) thus display a contrast ratio of 4.9:1 as compared to the ratio of 7:1 which would normally be expected if the screen were not presensitized.
  • the screen brightness under the indicated X-ray signal ⁇ irradiation would follow the dotted curves in Fig. 7.
  • the transient portions of the released luminous energy may be recorded photographically as hereinbefore described.
  • the objects of the invention have been achieved by vproviding a method for achieving a very bright iluoroscopi'c image while exposing the object being X-rayed to a minimum quantity of X-ray irradiation.
  • the screen presensitization may be so selected as to either 'increase or decrease the contrast obtainable in the image, if desired.
  • the screen 10 has been presensitized with substantially uniform intensity X-'rays and such a procedure will normally be desirable.
  • the screen presensitizing eld has been removed shortly after the presensitizing X-rays have been stopped. It should be understood that the iield and presensitizing X-rays could be removed substantially simultaneously, if desired, without impairing the operation. If the presensitizing X-rays are removed after the Tel'd is removed, the energy stored in the presensitized screen will be reduced correspondingly.

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  • Apparatus For Radiation Diagnosis (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Photo Coupler, Interrupter, Optical-To-Optical Conversion Devices (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US645695A 1957-03-13 1957-03-13 Method of operating x-ray device Expired - Lifetime US2885559A (en)

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