CA1119316A - Gamma ray camera - Google Patents
Gamma ray cameraInfo
- Publication number
- CA1119316A CA1119316A CA000323047A CA323047A CA1119316A CA 1119316 A CA1119316 A CA 1119316A CA 000323047 A CA000323047 A CA 000323047A CA 323047 A CA323047 A CA 323047A CA 1119316 A CA1119316 A CA 1119316A
- Authority
- CA
- Canada
- Prior art keywords
- screen
- photocathode
- scintillator
- output
- display screen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/161—Applications in the field of nuclear medicine, e.g. in vivo counting
- G01T1/164—Scintigraphy
- G01T1/1641—Static instruments for imaging the distribution of radioactivity in one or two dimensions using one or several scintillating elements; Radio-isotope cameras
- G01T1/1642—Static instruments for imaging the distribution of radioactivity in one or two dimensions using one or several scintillating elements; Radio-isotope cameras using a scintillation crystal and position sensing photodetector arrays, e.g. ANGER cameras
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/161—Applications in the field of nuclear medicine, e.g. in vivo counting
- G01T1/164—Scintigraphy
- G01T1/1641—Static instruments for imaging the distribution of radioactivity in one or two dimensions using one or several scintillating elements; Radio-isotope cameras
- G01T1/1645—Static instruments for imaging the distribution of radioactivity in one or two dimensions using one or several scintillating elements; Radio-isotope cameras using electron optical imaging means, e.g. image intensifier tubes, coordinate photomultiplier tubes, image converter
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
- H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
- H01J29/36—Photoelectric screens; Charge-storage screens
- H01J29/38—Photoelectric screens; Charge-storage screens not using charge storage, e.g. photo-emissive screen, extended cathode
- H01J29/385—Photocathodes comprising a layer which modified the wave length of impinging radiation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/92—Means forming part of the tube for the purpose of providing electrical connection to it
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J31/00—Cathode ray tubes; Electron beam tubes
- H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
- H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
- H01J31/505—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output flat tubes, e.g. proximity focusing tubes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/42—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis
- A61B6/4208—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
- A61B6/4258—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector for detecting non x-ray radiation, e.g. gamma radiation
Abstract
ABSTRACT OF THE DISCLOSURE
An Anger gamma ray Camera is improved by the substitution of a gamma ray sensitive, proximity type image intensifier tube for the scintillator screen in the Anger camera, the image intensifier tube having a negatively charged flat scintillator screen and a flat photocathode layer and a grounded, flat output phosphor display screen all of the same dimension (unity image magnification) and all within a grounded metallic tube envelope and having a metallic, inwardly concaved input window between the scintillator screen and the collimator.
An Anger gamma ray Camera is improved by the substitution of a gamma ray sensitive, proximity type image intensifier tube for the scintillator screen in the Anger camera, the image intensifier tube having a negatively charged flat scintillator screen and a flat photocathode layer and a grounded, flat output phosphor display screen all of the same dimension (unity image magnification) and all within a grounded metallic tube envelope and having a metallic, inwardly concaved input window between the scintillator screen and the collimator.
Description
3~6 BACKGROUND OF THE INVENTION
This invention relates to radiation detectors and more ~particularly to scintillation cameras and radioisotope imagina devices.
A scintillation camera haviny a collimator, a scintillatGr screen, and photo-multiplier tubes (PMT) coupled to the scintilla-tor was proposed by Hal O. Anger and is described and claimed in ¦ U. S. Patent No. 3,011,057. In the Anser camera the photo-¦¦multiplier tubes are connected to circuitry which utilizes their ~¦ !
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1 their signals to determine the position of each scintillation
This invention relates to radiation detectors and more ~particularly to scintillation cameras and radioisotope imagina devices.
A scintillation camera haviny a collimator, a scintillatGr screen, and photo-multiplier tubes (PMT) coupled to the scintilla-tor was proposed by Hal O. Anger and is described and claimed in ¦ U. S. Patent No. 3,011,057. In the Anser camera the photo-¦¦multiplier tubes are connected to circuitry which utilizes their ~¦ !
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1 their signals to determine the position of each scintillation
2 and to generate light spots or dots on the face of an oscillo-
3 1 scope at corresponding positions.
4 ¦ The Anger PMT circuitry detects both the centroid and pulse S 1 height of a gamma ray flash in the scintillator screen. The 6 1 centroid location is given by x, y coordinates and the brightness ¦ or amplitude (or effective pulse height) of the flash is given 8 1 by z. Therefore, the Anger camera provides the x, y, z repre-9 1 sentative characteristics of the incident gamma ray. This is done serially, that is each gamma ray flash as represented by 11 ¦ this signal:pulse at the PMT output is analyzed one by one.
12 1 The Anger camera, although widely used, has several basic ¦ limitations. These are: ;
14 ¦ ~a) Poor intrinsic spatial resolution (uncertainties 15 ¦ in the values of x and y~.
16 ¦ ~b) Poor pulse helght resolution ~uncertainties in the 17 ¦ values of ~).
18 1 (c) Poor stability.
19 ld) Poor count rate. i~-:
The basic limitations are more fully discussed below:
21 1 (a) Intrinsic spatial resolution. The spatial resolution 22 10f the Anger camera has an extrinsic part which is related to 23 ¦external geometrical factors such as the object distance from 24 ¦the camera, the collimator design, etc. The spatial resolution ¦of the Anger camera also has an intrinsic part which is due to 26 ¦the way a gamma ray loses its energy in the scintillator and the 27 ¦statistics of the division of light photons from each scintilla-28 ¦tion among the PMTs and the statistics of the generation of the 29 ¦photoelectrons at each PMT. The intrinsic part of lower gamma ray energy levels is almost entirely due to the statistics of the 31 ¦division of light photons and the generations of photoelectrons at 32 the photocathodes of the PMTs. That is, the statistics make the .:
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1 ¦ location of the centroid of the fash unccrtain. This situation 2 1 becomcs worse as the gamma ray energy decreases. This is why the 3 ¦ Anger camcra cannot image low energy gamma rays very well. The 4 ¦ spatial resolution steadily worsens at gamma ray energy levels ¦ below 500 Kev. The use of higher photocathode efficiency PMTs 6 ¦ improves the spatial resolution somewha~. The use of more PMTs 7 ¦ per camera also improves the spatial resolution, but it is done 8 1 at the expense of stability and cost of equipment. Current 9 1 camera's intrinsic spatial resolution at gamma ray energies -~
above 200 Kev. operates at around 5 to 6 mm as measured by the 11 ¦ full width at half maximum (FWHM) of the line distribution 12 ¦ function, which is only marginally useful for many practical 13 1 applications in nuclear medicine.
14 ¦ (b) Pulse height resolution. The Anger camera's pulse 1 height resolution is also marginal such that a large fraction of 16 ¦ th~ unwanted events due to Compton scattered gamma rays are 17 1 accepted as true signals. This problem worsens at lower gamma 18 ¦ ray cnergies, because the energy separation between the primary 19 1 gamma ray and Compton scattered gamma rays becomes smaller.
1 The use of higher photocathode efficiency P.lTs improves the pulse 21 1 height resolution somewhat but not er.ough.
22 1 (c) Stability. Stability of the Anaer camera is dependent 23 ¦ on the gain stability of the PMTs. The mcre P`:Ts in each camera, 24 1 the more control is the problem. Each one percent drift in 1 the PMT voltage supply will cause more than lO~ drift in the gain 26 ¦ of the PMT.
27 1 (d) Count Rate. The count rate capability of the Anaer 28 ¦ camera in handling larger numbers of events in a short time 29 1 period is dependent on the decay time of the thallium-activated sodium iodide NaI (Tl) scintillator crystal and thc dynamic 31 rcs~onse of the pulse amplifier and the pulse-sha~in~ networ~s. ..
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In various attempts to overcome one or more of the above-2 listed limitations of the Anger camera irnage intensifier tubes 3 were introduced between the scintillator and the photodetectors.
4 Such scintillation camera designs based on the use of image intensifier tubes are numerous and many prototype cameras have been reported. Some reports appeared e~en-before the invention 7 of the Anger camera. Several cameras were made available 8 commercially but none at this day survived in the market p]ace 9 against the universally accepted Anger camera. The failure of thesecameras can be attributed ~o inferior overall performance 11 against the Anger camera. Detailed reviews of this art have 12 been given by Muehllehner (S.P.I.E., Vol. 78, pages 113-117 l3 (1976)) and by Moody, et al (Proc. I.E.E.E., Vol. 58, pages 14 217-242 (1970)). See also U. S. Patents Nos. 3,6~3,185 (Muehllehner) and 3,531,651 (Lieber, et al).
16 ~here are several major shortcomings as compared to the 17 nger camera shared by virtually all such scintillation cameras 18 incorporating image intensifier tubes. These are: ~`;
1) Poor ~ulse heiqht statistics such that there is little or no ability for rejecting the Compton scattered eve~ts. This 21 generally results in degraded image contrast and poor visibility 22 of cold spots - - - - rendering the camera ineffective in 23 general use. The cause of this is either due to the inability 24 of the design of the camera to provide pulse height analysis or due to poor collection and utilization characteristics of 26 the visible photons from each scintillation flash in the 27 scintillator screen.
28 2) Measurable degrees of image distortion such that the 29 camera is not able to provide a high degree of accuracy in the configuration of the image presented. This renders the camera 3~
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1~193~6 undesirable in studies such as volumetric studies. The cause 2 of this is due to the inherent image distortion in the inverter 3 and minifying type image intensifier tube used and the curved scintillator screen used in the camera.
3) Noise pulses in Image Intensifier Tubes. Noise 6 sources which are not scintillation in ôrigin are problems 7 common in image intensifier tubes. For low activity gamma-8 ray imaging, this is especially important. A common fault of 9 the cameras in the prior art is the large number of exposed, external, negative high-voltage areas which are potential points :
11 of trouble for corona discharge and induced noise pulses.
12 4) Bulk and Implosion Hazard and High Voltage Hazard.
13 Bulk is a commonly shared problem. Inherent in the bulk is the 14 large vacuum space enclosed in the image intensifier tubes, which is a potential hazard for implosion and scattered glass 16 fragments.
17 The high voltage which must be supplied across these 18 image intensifier tubes poses another hazard. One end of these 19 tubes must be operated at high voltage and the other end at ground potential. The high voltage end must be properly 21 insulated so that it will not be a shock hazard. It should 22 also not be a noise source as mentioned above. Prequently the 23 insulation is so thick at the photocathode end that the 24 collimator can not be placed close enough to the scintillator screen to minimize the extrinsic spatial resolution loss for the 26 camera to take advantage of the gained intrinsic spatial 27 resolution.
28 The closest prior art to the present invention are 29 disclosed in U. S. Patent No. 3,683,185 (Muehllehner) and U. S. Patent No. 3,531,651 (Lieber, et al). The Muehllehner
12 1 The Anger camera, although widely used, has several basic ¦ limitations. These are: ;
14 ¦ ~a) Poor intrinsic spatial resolution (uncertainties 15 ¦ in the values of x and y~.
16 ¦ ~b) Poor pulse helght resolution ~uncertainties in the 17 ¦ values of ~).
18 1 (c) Poor stability.
19 ld) Poor count rate. i~-:
The basic limitations are more fully discussed below:
21 1 (a) Intrinsic spatial resolution. The spatial resolution 22 10f the Anger camera has an extrinsic part which is related to 23 ¦external geometrical factors such as the object distance from 24 ¦the camera, the collimator design, etc. The spatial resolution ¦of the Anger camera also has an intrinsic part which is due to 26 ¦the way a gamma ray loses its energy in the scintillator and the 27 ¦statistics of the division of light photons from each scintilla-28 ¦tion among the PMTs and the statistics of the generation of the 29 ¦photoelectrons at each PMT. The intrinsic part of lower gamma ray energy levels is almost entirely due to the statistics of the 31 ¦division of light photons and the generations of photoelectrons at 32 the photocathodes of the PMTs. That is, the statistics make the .:
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.
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1 ¦ location of the centroid of the fash unccrtain. This situation 2 1 becomcs worse as the gamma ray energy decreases. This is why the 3 ¦ Anger camcra cannot image low energy gamma rays very well. The 4 ¦ spatial resolution steadily worsens at gamma ray energy levels ¦ below 500 Kev. The use of higher photocathode efficiency PMTs 6 ¦ improves the spatial resolution somewha~. The use of more PMTs 7 ¦ per camera also improves the spatial resolution, but it is done 8 1 at the expense of stability and cost of equipment. Current 9 1 camera's intrinsic spatial resolution at gamma ray energies -~
above 200 Kev. operates at around 5 to 6 mm as measured by the 11 ¦ full width at half maximum (FWHM) of the line distribution 12 ¦ function, which is only marginally useful for many practical 13 1 applications in nuclear medicine.
14 ¦ (b) Pulse height resolution. The Anger camera's pulse 1 height resolution is also marginal such that a large fraction of 16 ¦ th~ unwanted events due to Compton scattered gamma rays are 17 1 accepted as true signals. This problem worsens at lower gamma 18 ¦ ray cnergies, because the energy separation between the primary 19 1 gamma ray and Compton scattered gamma rays becomes smaller.
1 The use of higher photocathode efficiency P.lTs improves the pulse 21 1 height resolution somewhat but not er.ough.
22 1 (c) Stability. Stability of the Anaer camera is dependent 23 ¦ on the gain stability of the PMTs. The mcre P`:Ts in each camera, 24 1 the more control is the problem. Each one percent drift in 1 the PMT voltage supply will cause more than lO~ drift in the gain 26 ¦ of the PMT.
27 1 (d) Count Rate. The count rate capability of the Anaer 28 ¦ camera in handling larger numbers of events in a short time 29 1 period is dependent on the decay time of the thallium-activated sodium iodide NaI (Tl) scintillator crystal and thc dynamic 31 rcs~onse of the pulse amplifier and the pulse-sha~in~ networ~s. ..
3~
.
~119316 ',, .
In various attempts to overcome one or more of the above-2 listed limitations of the Anger camera irnage intensifier tubes 3 were introduced between the scintillator and the photodetectors.
4 Such scintillation camera designs based on the use of image intensifier tubes are numerous and many prototype cameras have been reported. Some reports appeared e~en-before the invention 7 of the Anger camera. Several cameras were made available 8 commercially but none at this day survived in the market p]ace 9 against the universally accepted Anger camera. The failure of thesecameras can be attributed ~o inferior overall performance 11 against the Anger camera. Detailed reviews of this art have 12 been given by Muehllehner (S.P.I.E., Vol. 78, pages 113-117 l3 (1976)) and by Moody, et al (Proc. I.E.E.E., Vol. 58, pages 14 217-242 (1970)). See also U. S. Patents Nos. 3,6~3,185 (Muehllehner) and 3,531,651 (Lieber, et al).
16 ~here are several major shortcomings as compared to the 17 nger camera shared by virtually all such scintillation cameras 18 incorporating image intensifier tubes. These are: ~`;
1) Poor ~ulse heiqht statistics such that there is little or no ability for rejecting the Compton scattered eve~ts. This 21 generally results in degraded image contrast and poor visibility 22 of cold spots - - - - rendering the camera ineffective in 23 general use. The cause of this is either due to the inability 24 of the design of the camera to provide pulse height analysis or due to poor collection and utilization characteristics of 26 the visible photons from each scintillation flash in the 27 scintillator screen.
28 2) Measurable degrees of image distortion such that the 29 camera is not able to provide a high degree of accuracy in the configuration of the image presented. This renders the camera 3~
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.
.
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1~193~6 undesirable in studies such as volumetric studies. The cause 2 of this is due to the inherent image distortion in the inverter 3 and minifying type image intensifier tube used and the curved scintillator screen used in the camera.
3) Noise pulses in Image Intensifier Tubes. Noise 6 sources which are not scintillation in ôrigin are problems 7 common in image intensifier tubes. For low activity gamma-8 ray imaging, this is especially important. A common fault of 9 the cameras in the prior art is the large number of exposed, external, negative high-voltage areas which are potential points :
11 of trouble for corona discharge and induced noise pulses.
12 4) Bulk and Implosion Hazard and High Voltage Hazard.
13 Bulk is a commonly shared problem. Inherent in the bulk is the 14 large vacuum space enclosed in the image intensifier tubes, which is a potential hazard for implosion and scattered glass 16 fragments.
17 The high voltage which must be supplied across these 18 image intensifier tubes poses another hazard. One end of these 19 tubes must be operated at high voltage and the other end at ground potential. The high voltage end must be properly 21 insulated so that it will not be a shock hazard. It should 22 also not be a noise source as mentioned above. Prequently the 23 insulation is so thick at the photocathode end that the 24 collimator can not be placed close enough to the scintillator screen to minimize the extrinsic spatial resolution loss for the 26 camera to take advantage of the gained intrinsic spatial 27 resolution.
28 The closest prior art to the present invention are 29 disclosed in U. S. Patent No. 3,683,185 (Muehllehner) and U. S. Patent No. 3,531,651 (Lieber, et al). The Muehllehner
-5-1 camera consists of a flat crystal scintillator screen external 2 to a large diameter image intensifier tube of the electrostatic 3 inverter with minified output design with a curved input 4 photocathode surface, two additional tubes of the electrostatic inverter type design all with a curved input photocathode and curved output phosphor, and a positional sensing detector and 7 circuit. In one of the Muehllehner embodiments and in the 8 Lieber, et al patent are also disclosed designs with a curved 9 scintillator screen inside the image intensifier tube and curved photocathode deposited on-the screen. All of these 11 cameras suffer at least the faults discussed at paragraphs 2, 12 3 and 4 above.
13 The electrostatic inverter type of image intensifier 14 tubes introduce a substantial amount of spatial distortion making accurate volumetric determination with this camera 16 doubtful. Thc high voltage must be supplied to the input end 17 making insulation and placement of the collimato~ difficult.
18 The placement of the sclntillator screen outside of the tube 19 causes inefficient optical coupling to the photocathode and in turn causes poor pulse height resolution and poor spatial 21 resolution. Neither Muehllehner, nor Lieber, et al, show how 22 the internal crystal scintillator can be properly used and 23 coupled to the photocathode.
The above and other disadvantages of prior art image 26 intensifier gamma ray cameras are overcome by the present 27 invention of a modified Anger camera comprising a collimator, 28 a flat scintillator screen aligned with the collimator, a first 29 lat photocathode disposed with its flat surfaces parallel and adjacent to the scintillator screen, a first flat output phosphor
13 The electrostatic inverter type of image intensifier 14 tubes introduce a substantial amount of spatial distortion making accurate volumetric determination with this camera 16 doubtful. Thc high voltage must be supplied to the input end 17 making insulation and placement of the collimato~ difficult.
18 The placement of the sclntillator screen outside of the tube 19 causes inefficient optical coupling to the photocathode and in turn causes poor pulse height resolution and poor spatial 21 resolution. Neither Muehllehner, nor Lieber, et al, show how 22 the internal crystal scintillator can be properly used and 23 coupled to the photocathode.
The above and other disadvantages of prior art image 26 intensifier gamma ray cameras are overcome by the present 27 invention of a modified Anger camera comprising a collimator, 28 a flat scintillator screen aligned with the collimator, a first 29 lat photocathode disposed with its flat surfaces parallel and adjacent to the scintillator screen, a first flat output phosphor
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, ~, : ;: , ~ 16 1 ¦display screen which is spaced apart from and parallel to the photocathode and on its side opposite from the scintillator 3 ¦screen, an output window upon which the first display screen is 4 ¦mounted, a metallic input window, an open-ended, hollow metallic S ¦tube envelope surrounding the scintillator screen and the 6 ¦ photocathode and which is closed at one end by the output window
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, ~, : ;: , ~ 16 1 ¦display screen which is spaced apart from and parallel to the photocathode and on its side opposite from the scintillator 3 ¦screen, an output window upon which the first display screen is 4 ¦mounted, a metallic input window, an open-ended, hollow metallic S ¦tube envelope surrounding the scintillator screen and the 6 ¦ photocathode and which is closed at one end by the output window
7 and at the other end by the input window and which is evacuated,
8 and means for applying an accelerating electrostatic potential
9 between the display screen and the photocathode. The collimator is located exterior to the tube envelope in one embodiment and :
Il is spaced closely adjacent to the input window. In another 12 embodiment the collimator is mounted within the tube envelope 13 and ahead of the scintillator screen, taken in the direction of l4 the impinying radiation.
IS In the preferred embodiment of the invention the 16 scintillation screen, the photocathode and the output display 17 screen have substantially the same diagonal dimensions. A
18 plurality of photo-detectors are optically coupled to the output l9 display screen through the output window. These photo-detectors, such as photo-multiplier tubes, are connected to conventional 21 Anger camera circuitry which processes the signals emanating 22 from the photo-multiplier tubes, and produces an image 23 corresponding to the light image gen,erated by the incident 24 radiation on the scintillator. The generation of this image is substantially the same as is done in the Anger Patent No.
26 3,011,057, however, because of the increased conversion 27 efficiency of the image intensifier tube of the invention and 28 because the scintillator's crystal is located immediately 29 adjacent to the photocathode layer, greater pulse height .
statistics and thus greater spatial resolution are achieved.
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1 In the preferred embodiment of the invention each incident 2 gamma ray photon produces a multitude of photons at the output 3 display screen which can be accurately triangulated by the photo-4 multiplier tubes. This also allows the photo-multip3ier tube S circuit to easily discriminate between direct, incident radiation 6 and scattered radiation. ,~
7 In a modification of the preferred embodiment the 8 scintillator screen, the photocathode and the output display 9 screen are segmented and the circuitry associated with the photo-multiplier tubes of the various segments operate indepen-11 dently from each other so that each segment operates as a 12 separate gamma ray camera.
13 In still another embodiment of the invention a second ;' 14 stage of amplification is introduced. In this two stage version of the invention the first output display scrqen is mounted on 16 one side of a fiber optic plate rather than on the output window.
17 A second photocathode is mounted on the opposite side of the 18 fiber optic plate. A second output display screen is mounted 19 on the output window and is spaced apart and parallel to the second photocathode. Additional means are utilized for applying 21 electrostatic potential between the second photocathode and a 22 second output display screen. This arrangement gives even 23 greater capability for detecting between direct and scattered 24 radiation.
25 In all of the above-described embodiments the input window 26 is metallic and is preferably made of Type 17-7 PH stainless 27 s,teel. This steel has been found to have highly desirable x-ray 28 input characteristics as more fully described in the applicant's 29 U.S. Patent 4,140,900. The essentially ali metallic and "
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of the tube minimizes the danger of implosion. The small vacuum space enclosed by the tube represents much smaller stored potential energy as compared with a conventional t:ube which further minimizes implosion danger. ~urthermore, if punctured, the metal behaves differen-tly from glass and the air simply leaks in without fracturing or imploding.
It is therefore an object of the present invention to provide an improved Anger type gamma ray camera utilizing a proximity type image intensifier tube;
It is still another object of the present invention to provide an improved Anger type gamma ray camera having greater capability for distinguishing between incident and scattered radiation.
It is a still further ob~ect of the invention to provide an improved ~nger type yamma ra,y camera having greater spatial resolution capabilities.
In accordance with the present invention therefore, ;
there is provided an improved scintillation camera of the type having a radiation collimator, scintillator means aligned with the collimator for converting radiation passing through the collimator and impinging upon the scintillator means into a corresponding light pattern, the scintillator means including a scintillator screen and an output screen for displaying the light patterns, a plurality of photo-electric detectors disposed in view of substantially co-extensive portions of the output screen, and means connected to the photo-electric detectors for receiving signals emitted from them and for translating such signals into relatively ~m/~
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displaced images of the light patterns, wherein the improvement resides in the scintillator means which comprise:
a flat scintillator screen, a first flat photocathode clisposed with its flat surfaces parallel to and adjacent to t:he scintillator screen, a first flat output phosphor display screen which constitutes the light output screen of the scintillàtor means, the display screen having its flat surEaces parallel to and spaced apart from the flat surfaces of the photocathode and on its side opposite from the scintillator screen, an output window on which the display screen is mounted, a metallic input window, means for applying an accelerating electrostatic potential between the display screen and the photocathode, and an open ended, hollow, evacuated envelope surrounding the scintillator screen and the photocathode and which is closed at one end by the output window and at the other end by the input window.
The foregoing and other objectives, features ~-and advantages of the invention will be more readily understood upon consideration of the following detailed description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings.
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I BRIEF DESCRIPTION OF THE DRAWINGS
2 FIGURE l is a diagrammatic vertical, sectional view, with 3 portions broken away of the gamma ray camera according to the 4 invention;
FIGURES 2 and 3 are graphical illustrations for use in 6 describing the invention;
: FIGURE 4 is a diagrammatic illustration of a second, two 8 stage embodiment of the invention;
9 FIGURE 5 is a plan view of the output display screen of still another modified embodiment of the invention;
11 FIGURE 6 is a vertical, sectional view of a combined 12 eollimator-scintillator screen assembly of still another :~
13 embodiment of the invention;
14 FIGURE 7 is an enlarged, vertieal, ~eetional view of a detall of the seintillator sereen assembly of the embodinlent 16 shown in FIGURE l.
17 FIGURE 8 is a detailed vertieal view, in section, of the 18 image intensifier tube of the invention; .
19 FIGURE 9 is a vertical, sectional view, taken generally long the line 9-9 in Figure 8, of the image intensifier tube 21 ceording to the invention; and 22 FIGURE lO is a diagrammatic view of a modification of 23 he embodiment depicted in Figure 4.
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Il is spaced closely adjacent to the input window. In another 12 embodiment the collimator is mounted within the tube envelope 13 and ahead of the scintillator screen, taken in the direction of l4 the impinying radiation.
IS In the preferred embodiment of the invention the 16 scintillation screen, the photocathode and the output display 17 screen have substantially the same diagonal dimensions. A
18 plurality of photo-detectors are optically coupled to the output l9 display screen through the output window. These photo-detectors, such as photo-multiplier tubes, are connected to conventional 21 Anger camera circuitry which processes the signals emanating 22 from the photo-multiplier tubes, and produces an image 23 corresponding to the light image gen,erated by the incident 24 radiation on the scintillator. The generation of this image is substantially the same as is done in the Anger Patent No.
26 3,011,057, however, because of the increased conversion 27 efficiency of the image intensifier tube of the invention and 28 because the scintillator's crystal is located immediately 29 adjacent to the photocathode layer, greater pulse height .
statistics and thus greater spatial resolution are achieved.
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1 In the preferred embodiment of the invention each incident 2 gamma ray photon produces a multitude of photons at the output 3 display screen which can be accurately triangulated by the photo-4 multiplier tubes. This also allows the photo-multip3ier tube S circuit to easily discriminate between direct, incident radiation 6 and scattered radiation. ,~
7 In a modification of the preferred embodiment the 8 scintillator screen, the photocathode and the output display 9 screen are segmented and the circuitry associated with the photo-multiplier tubes of the various segments operate indepen-11 dently from each other so that each segment operates as a 12 separate gamma ray camera.
13 In still another embodiment of the invention a second ;' 14 stage of amplification is introduced. In this two stage version of the invention the first output display scrqen is mounted on 16 one side of a fiber optic plate rather than on the output window.
17 A second photocathode is mounted on the opposite side of the 18 fiber optic plate. A second output display screen is mounted 19 on the output window and is spaced apart and parallel to the second photocathode. Additional means are utilized for applying 21 electrostatic potential between the second photocathode and a 22 second output display screen. This arrangement gives even 23 greater capability for detecting between direct and scattered 24 radiation.
25 In all of the above-described embodiments the input window 26 is metallic and is preferably made of Type 17-7 PH stainless 27 s,teel. This steel has been found to have highly desirable x-ray 28 input characteristics as more fully described in the applicant's 29 U.S. Patent 4,140,900. The essentially ali metallic and "
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of the tube minimizes the danger of implosion. The small vacuum space enclosed by the tube represents much smaller stored potential energy as compared with a conventional t:ube which further minimizes implosion danger. ~urthermore, if punctured, the metal behaves differen-tly from glass and the air simply leaks in without fracturing or imploding.
It is therefore an object of the present invention to provide an improved Anger type gamma ray camera utilizing a proximity type image intensifier tube;
It is still another object of the present invention to provide an improved Anger type gamma ray camera having greater capability for distinguishing between incident and scattered radiation.
It is a still further ob~ect of the invention to provide an improved ~nger type yamma ra,y camera having greater spatial resolution capabilities.
In accordance with the present invention therefore, ;
there is provided an improved scintillation camera of the type having a radiation collimator, scintillator means aligned with the collimator for converting radiation passing through the collimator and impinging upon the scintillator means into a corresponding light pattern, the scintillator means including a scintillator screen and an output screen for displaying the light patterns, a plurality of photo-electric detectors disposed in view of substantially co-extensive portions of the output screen, and means connected to the photo-electric detectors for receiving signals emitted from them and for translating such signals into relatively ~m/~
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displaced images of the light patterns, wherein the improvement resides in the scintillator means which comprise:
a flat scintillator screen, a first flat photocathode clisposed with its flat surfaces parallel to and adjacent to t:he scintillator screen, a first flat output phosphor display screen which constitutes the light output screen of the scintillàtor means, the display screen having its flat surEaces parallel to and spaced apart from the flat surfaces of the photocathode and on its side opposite from the scintillator screen, an output window on which the display screen is mounted, a metallic input window, means for applying an accelerating electrostatic potential between the display screen and the photocathode, and an open ended, hollow, evacuated envelope surrounding the scintillator screen and the photocathode and which is closed at one end by the output window and at the other end by the input window.
The foregoing and other objectives, features ~-and advantages of the invention will be more readily understood upon consideration of the following detailed description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings.
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I BRIEF DESCRIPTION OF THE DRAWINGS
2 FIGURE l is a diagrammatic vertical, sectional view, with 3 portions broken away of the gamma ray camera according to the 4 invention;
FIGURES 2 and 3 are graphical illustrations for use in 6 describing the invention;
: FIGURE 4 is a diagrammatic illustration of a second, two 8 stage embodiment of the invention;
9 FIGURE 5 is a plan view of the output display screen of still another modified embodiment of the invention;
11 FIGURE 6 is a vertical, sectional view of a combined 12 eollimator-scintillator screen assembly of still another :~
13 embodiment of the invention;
14 FIGURE 7 is an enlarged, vertieal, ~eetional view of a detall of the seintillator sereen assembly of the embodinlent 16 shown in FIGURE l.
17 FIGURE 8 is a detailed vertieal view, in section, of the 18 image intensifier tube of the invention; .
19 FIGURE 9 is a vertical, sectional view, taken generally long the line 9-9 in Figure 8, of the image intensifier tube 21 ceording to the invention; and 22 FIGURE lO is a diagrammatic view of a modification of 23 he embodiment depicted in Figure 4.
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1 ¦ DESCRIPTION OF CERT~IN PREFERRED EMBODIMENTS
2 ¦ Referring now more particularly to Fiyure 1, the gamma 3 ray camera according to the invention is illustrated. In this 4 1 simplified diagram, a radiation emitting body lO, such as a 1 human patient containing a small amount o~ radioactive isotope, 6 ¦ emits radiation stimuli 12 in terms of gamma-ray photons which ~
7 ¦ impinge on a parallel hole collimator 14. The collimator is made 8 1 of a high atomic number material such as lead, tungston or ¦ tantalum which stops the gamma rays 12 except where a through 1 hole 16 is provided.
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1 ¦ DESCRIPTION OF CERT~IN PREFERRED EMBODIMENTS
2 ¦ Referring now more particularly to Fiyure 1, the gamma 3 ray camera according to the invention is illustrated. In this 4 1 simplified diagram, a radiation emitting body lO, such as a 1 human patient containing a small amount o~ radioactive isotope, 6 ¦ emits radiation stimuli 12 in terms of gamma-ray photons which ~
7 ¦ impinge on a parallel hole collimator 14. The collimator is made 8 1 of a high atomic number material such as lead, tungston or ¦ tantalum which stops the gamma rays 12 except where a through 1 hole 16 is provided.
11 ¦ The collimator is mounted at one end of a casing 18 which ;
12 1 surrounds the camera 20 of the invention. Behind the collimator
13 1 14, with;,respect to the direction of travel of the gamma rays
14 ¦ 12, i5 mounted an image intensifying tube. The image intensifier 1 tube comprises a metallic, typically type 304 stainless steel, 16 vacuum tube envelope 28 and a metallic, inwardly concave input 17 1 window 22 immediately adjacent to the collimator 14. The 18 ¦ window 22 is made of a specially chosen metal foil or alloy 19 ¦metal foil in the family of iron, chromium, and nickel, and in ¦ some embodiments, additionally combinations of iron or nickel 21 ¦together with cobalt or vanadium. It is important to note that 22 1 these elements are not customarily recognized in the field as 23 ¦good gamma ray transmitting window materials in diagnostic 24 1 devices. By making the window thin, down to O.l mm in thickness, ¦ the applicant was able to achieve high gamma ray transmission 26 1 with t~nese materials and at the same time obtain the desired 27 ¦tensile strength. In particular, a foil made of 17-7 PH type 28 ¦ of precipitation hardened chromium-nickel stainless steel is 29 ¦ utilized in the preferred embodiment. This alloy is vacuum 1tight, high in tensile strength and has very attractive gamma 32 ~ ray transmission propcrties: high transmission to primary gamma ,, ::, . ' ~ :
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rays, low self-scattering, and reasonably absorbing with respect 2 to Compton scattered gamma rays. The window 22 i5 concaved into 3 the tube like a drum head.
The use of materials which are known for high gamma S transmission such as beryllium, aluminum and titanium for 6 example cause undesirable scattering.
one purpose of having a metallic window 2Z is that it 8 can be quite large in diameter with respect to the prior art 9 type of convex, glass window, without affecting the image quality.
In one embodiment, the window measures 0.1 mm thick, 25 cm by 11 25 cm and can withstand over 100 pounds per square inch of 12 xessure. The input window can be square, rectangular, or 13 circular in shape, since it is a high tensile strength material 14 and is under tension rather than compression.
Behind the input window 22, again taken in the direction 16 of travcl of the gamma ray radiation 12, is the scintillation 17 screen 24. This scintillation screen is mounted in a corona 18 shield and support ring 26 which, in turn, is mounted in the l9 metallic tube envelope 28. The envelope 28 is closed at the -front end by the input window 22 and at the opposite end by a 21 glass output window 30. On the side of the scintillation 22 screen 24 closest to the input window 22 is a reflective back 23 32 and on top of that is a metallieed support layer 34.
24 Referring now more particularly to Figure 7, the detailed 2~ construction of the scintillator-photocathode screen assembly is 26 illustrated. In the enlarged detailed view of Figure 7, it can 27 e seen that the screen 24, which is shown as a single crystal 28 slab, is provided with a metallized edge 36 which is in 29 electrical contact with a spring 38 mounted in the corona shield .
and support ring 26. The flat face of the crystal 24 opposite O; ~ . - . .
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from the metallized layer 34 and ~he reflective layer 32 is optionally covered with a barrier layer 40 of freshly vapor depositcd CsI~Na), CsI, bismuth ycrminate, or A1203 which all have similar indexes of refraction. On top of this layer 40 is deposited ~he photocat~ode layer 42, which is in electrical contact with the metallized edge 36.
Examples of appropriate materials to be used in this screen assembly are aluminum, aluminum oxide or titanium oxide for the reflecting layer 32, aluminum or chromium for the metallized layer 34 and CsI(Na) for the crystal 24. The layers 32 and 34 may be vapor deposited. The layers 32, 34 and 40 are typically thicker than 0.1u and thinner than 25u.
The crystal 24 can also be made of NaI(Tl). For equivalent gamma ray stopping power, a crystal made of Csl(Na) can be made thinner than NaI(Tl), however, for better pulse-height statis-tic~ NaI(T]) is used. The crystal can be vapor deposited on the reflcctive coating 32 and metallized substrate 34. The crystal can also be a single crystal slab.
When the crystal 24 is a single crystal slab cut from a single crystal ingot, and if the thickness is of the order of 1 to 2 mm or thicker, it may not be necessary to use the metallized substrate 34 for mechanical support. Since there . is usually extensive handling of the crystal slab prior to the tube assembly, a thin layer of freshly (just prior to final tube assembly) vapor deposïted CsI(Na), bismuth germinate, CsI
or A1203 as a barrier layer 40 on the scintillator screen is desirable. The purpose of the layer is to prevent the photo-cathode from being poisoned by surface impurities on the crystal. This barrier layer is especially important in the case of NaI(Tl) crystal 24 where the barrier layer is also used to minimize the vaporization or escape of TlI. However, it is important to point out here jk/c~
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1 that it is al50 the objcct of this invention tha~ the visible 2 photons from each scintillation are efficicntly collected by 3 the photocathode. This is achieved through the use of barrier 4 layer materials which have a matching index of refraction with S the scintillation crystal.
6 Another transparent and conductive layer may be 7 introduced between the barrier layer 40 and the photocathode 8 42 to provide improved electrical conductivity and surface 9 cleanliness. Materials such as Ti or Ni metal-may be used for this purpose.
11 The photocathode layer 42 can be Cs3Sb, that is industry 12 phosphor types S-9 or S-ll. Fabrication methods for this photocathode layer are well known. The applicant has found 14 good success with the pre-evaporated antimony method -- a thin layer of antimony is deposited on the scintillation screen 16 24 prior to the assembly of the tube and exhaust bake cycle, 17 and cesium vapor is introduced after the exhaust bake cycle 18 and at a processing temperature of 120 to 170C. ~igher 19 efficiency photocathodes such as multi-alkali antimonide can also be used. (KCs)3Sb, commonly known as bi-alkali photo-21 cathode, can also be used. The applicant found that (KCs)3Sb 22 can also be deposited with the pre-evaporated antimony method --23 introduction of potassium vapor is followed by the introduction 24 of cesium vapor and the photocathode 42, with a negative high potential. The remaining parts of the intensification tube 26 including the metallic envelope 28, are all operated at ground 27 potential. This concept of minimizing the surface area which 28 is negative with respect to the output screen results in re-29 duced field emission rate inside the tube and allows the tube 30 to be operable at higher voltages and thus higher brightness ~, :~ :
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1 gain. As previously mentioned above, reducing field emissions 2 is especially desirable in a gamma ray camera because of the 3 rclatively low rate of occurrence of incident stimuli. It al50 minimizes the danger of electrical shock to the patient or workers if one should somehow come in contact with the 6 exterior envelope of the tube.
7 The thick, high atomic number (Z) glass substrate 30 on 8 which the phosphor display screen 46 is deposited and which 9 forms one exterior end wall of the vacuum tube envelope 28, is attached to the tube envelope 28 by means of a collar 31 made 11 of an iron, nickel, chromium alloy, designated to the trade as 12 "Carpenter, No. 456". Since the thermal coefficient of expansion 13 of this alloy matcnes that of the glass and nearly matches that 14 of the tube envelope 28, the collar 31 can be fritted to the glass substrate 30 and welded to the tube envelope 28. The 16 thiekness of the scintillator sereen 2q is in the range of 17 O.S mm. to 50 mm. for a gamma ray energy range of 30 Kev to 511 18 Kev.
19 The eorona shield and support ring 26 is made of aluminum, with an aluminum oxide coating (Al203), and supports the 21 scintillator screen 24. This ring is in electrical contact with 22 the sereen 24 and the photocathode 42 whieh is deposited on the 23 sereen 24. The ring 26 is supported from the metal tube 24 envelope 28 on insulators 27 (see Figures 8 and 9) and is eonneeted to a high voltage power supply 44. The high voltage 26 power supply 44 is also eonnected to the tube envelope 28 whieh 27 is eleetrieally eonneeted to an output phosphor sereen 46 28 deposited on the interior flat surfaee of the output window 29 30. The ground terminal of the supply 44 is eonneeted to the ~nvelope 28 so that no shoek potential exists to the operator
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rays, low self-scattering, and reasonably absorbing with respect 2 to Compton scattered gamma rays. The window 22 i5 concaved into 3 the tube like a drum head.
The use of materials which are known for high gamma S transmission such as beryllium, aluminum and titanium for 6 example cause undesirable scattering.
one purpose of having a metallic window 2Z is that it 8 can be quite large in diameter with respect to the prior art 9 type of convex, glass window, without affecting the image quality.
In one embodiment, the window measures 0.1 mm thick, 25 cm by 11 25 cm and can withstand over 100 pounds per square inch of 12 xessure. The input window can be square, rectangular, or 13 circular in shape, since it is a high tensile strength material 14 and is under tension rather than compression.
Behind the input window 22, again taken in the direction 16 of travcl of the gamma ray radiation 12, is the scintillation 17 screen 24. This scintillation screen is mounted in a corona 18 shield and support ring 26 which, in turn, is mounted in the l9 metallic tube envelope 28. The envelope 28 is closed at the -front end by the input window 22 and at the opposite end by a 21 glass output window 30. On the side of the scintillation 22 screen 24 closest to the input window 22 is a reflective back 23 32 and on top of that is a metallieed support layer 34.
24 Referring now more particularly to Figure 7, the detailed 2~ construction of the scintillator-photocathode screen assembly is 26 illustrated. In the enlarged detailed view of Figure 7, it can 27 e seen that the screen 24, which is shown as a single crystal 28 slab, is provided with a metallized edge 36 which is in 29 electrical contact with a spring 38 mounted in the corona shield .
and support ring 26. The flat face of the crystal 24 opposite O; ~ . - . .
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from the metallized layer 34 and ~he reflective layer 32 is optionally covered with a barrier layer 40 of freshly vapor depositcd CsI~Na), CsI, bismuth ycrminate, or A1203 which all have similar indexes of refraction. On top of this layer 40 is deposited ~he photocat~ode layer 42, which is in electrical contact with the metallized edge 36.
Examples of appropriate materials to be used in this screen assembly are aluminum, aluminum oxide or titanium oxide for the reflecting layer 32, aluminum or chromium for the metallized layer 34 and CsI(Na) for the crystal 24. The layers 32 and 34 may be vapor deposited. The layers 32, 34 and 40 are typically thicker than 0.1u and thinner than 25u.
The crystal 24 can also be made of NaI(Tl). For equivalent gamma ray stopping power, a crystal made of Csl(Na) can be made thinner than NaI(Tl), however, for better pulse-height statis-tic~ NaI(T]) is used. The crystal can be vapor deposited on the reflcctive coating 32 and metallized substrate 34. The crystal can also be a single crystal slab.
When the crystal 24 is a single crystal slab cut from a single crystal ingot, and if the thickness is of the order of 1 to 2 mm or thicker, it may not be necessary to use the metallized substrate 34 for mechanical support. Since there . is usually extensive handling of the crystal slab prior to the tube assembly, a thin layer of freshly (just prior to final tube assembly) vapor deposïted CsI(Na), bismuth germinate, CsI
or A1203 as a barrier layer 40 on the scintillator screen is desirable. The purpose of the layer is to prevent the photo-cathode from being poisoned by surface impurities on the crystal. This barrier layer is especially important in the case of NaI(Tl) crystal 24 where the barrier layer is also used to minimize the vaporization or escape of TlI. However, it is important to point out here jk/c~
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1 that it is al50 the objcct of this invention tha~ the visible 2 photons from each scintillation are efficicntly collected by 3 the photocathode. This is achieved through the use of barrier 4 layer materials which have a matching index of refraction with S the scintillation crystal.
6 Another transparent and conductive layer may be 7 introduced between the barrier layer 40 and the photocathode 8 42 to provide improved electrical conductivity and surface 9 cleanliness. Materials such as Ti or Ni metal-may be used for this purpose.
11 The photocathode layer 42 can be Cs3Sb, that is industry 12 phosphor types S-9 or S-ll. Fabrication methods for this photocathode layer are well known. The applicant has found 14 good success with the pre-evaporated antimony method -- a thin layer of antimony is deposited on the scintillation screen 16 24 prior to the assembly of the tube and exhaust bake cycle, 17 and cesium vapor is introduced after the exhaust bake cycle 18 and at a processing temperature of 120 to 170C. ~igher 19 efficiency photocathodes such as multi-alkali antimonide can also be used. (KCs)3Sb, commonly known as bi-alkali photo-21 cathode, can also be used. The applicant found that (KCs)3Sb 22 can also be deposited with the pre-evaporated antimony method --23 introduction of potassium vapor is followed by the introduction 24 of cesium vapor and the photocathode 42, with a negative high potential. The remaining parts of the intensification tube 26 including the metallic envelope 28, are all operated at ground 27 potential. This concept of minimizing the surface area which 28 is negative with respect to the output screen results in re-29 duced field emission rate inside the tube and allows the tube 30 to be operable at higher voltages and thus higher brightness ~, :~ :
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1 gain. As previously mentioned above, reducing field emissions 2 is especially desirable in a gamma ray camera because of the 3 rclatively low rate of occurrence of incident stimuli. It al50 minimizes the danger of electrical shock to the patient or workers if one should somehow come in contact with the 6 exterior envelope of the tube.
7 The thick, high atomic number (Z) glass substrate 30 on 8 which the phosphor display screen 46 is deposited and which 9 forms one exterior end wall of the vacuum tube envelope 28, is attached to the tube envelope 28 by means of a collar 31 made 11 of an iron, nickel, chromium alloy, designated to the trade as 12 "Carpenter, No. 456". Since the thermal coefficient of expansion 13 of this alloy matcnes that of the glass and nearly matches that 14 of the tube envelope 28, the collar 31 can be fritted to the glass substrate 30 and welded to the tube envelope 28. The 16 thiekness of the scintillator sereen 2q is in the range of 17 O.S mm. to 50 mm. for a gamma ray energy range of 30 Kev to 511 18 Kev.
19 The eorona shield and support ring 26 is made of aluminum, with an aluminum oxide coating (Al203), and supports the 21 scintillator screen 24. This ring is in electrical contact with 22 the sereen 24 and the photocathode 42 whieh is deposited on the 23 sereen 24. The ring 26 is supported from the metal tube 24 envelope 28 on insulators 27 (see Figures 8 and 9) and is eonneeted to a high voltage power supply 44. The high voltage 26 power supply 44 is also eonnected to the tube envelope 28 whieh 27 is eleetrieally eonneeted to an output phosphor sereen 46 28 deposited on the interior flat surfaee of the output window 29 30. The ground terminal of the supply 44 is eonneeted to the ~nvelope 28 so that no shoek potential exists to the operator
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~, As mentioned above, the corona shield and support ring 6 26 for the scintillator and photocathode in this invention is 4 suspended from the tube envelope 28 between the input window 22 and the output screen 46 by the several insulating posts 27.
6 One or more of these posts may be hollow in the center to allow 7 an insulated high voltage cable 29 from the source 44 to be 8 inserted to provide the scintillator 24 with high voltage.
9 To reduce charges accumulated on the insulating posts 27, they are coated with a slightly conductive material such 11 as chrome oxide which bleeds off the accumulated charge by 12 providing a leakage path of better than 20 ~v/cm.
13 The output phosphor screen 46 can be made of well known 14 phosphor types P-lS or P-16 with the standard thin aluminum film coating on the vacuum side. These phosphors are considered
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~, As mentioned above, the corona shield and support ring 6 26 for the scintillator and photocathode in this invention is 4 suspended from the tube envelope 28 between the input window 22 and the output screen 46 by the several insulating posts 27.
6 One or more of these posts may be hollow in the center to allow 7 an insulated high voltage cable 29 from the source 44 to be 8 inserted to provide the scintillator 24 with high voltage.
9 To reduce charges accumulated on the insulating posts 27, they are coated with a slightly conductive material such 11 as chrome oxide which bleeds off the accumulated charge by 12 providing a leakage path of better than 20 ~v/cm.
13 The output phosphor screen 46 can be made of well known 14 phosphor types P-lS or P-16 with the standard thin aluminum film coating on the vacuum side. These phosphors are considered
16 relatively fast in their response time. This fast response is
17 needed when each individual gamma ray scintillation flash is
18 examined serially on a one by one basis by both its flash brightness (pulse height) on the output screen 46 and by the centroid or the weighted average location of the flash on the 21 screen.
22 Optically coupled to the exterior flat surface of the 23 output window 30 by means of light guides 48 are a plurality of 24 photo-multiplier tubes 50. These tubes, in turn, are connected to a triangulation and pulse height analyzing circuit 52. The 26 arrangement of the photo-multiplier tubes 50 and the circuitry of 2a 1 .l 31 . ., . , .. . . : . : . :
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1 the position locating or triangulation and pulse height analyzing 2 network 52 are well known to those skilled in the art and in 3 particular are described,with reference to Figure 2 in Anger 4 Patent No. 3,011,057 or with reference to Figures S and 6 of S Muehllehner Patent ~o. 3,683,185 and hence will not be described 6 in greater detail here. The output of the position network 7 52 is supplied to an appropriate display such as a cathode ray 8 tube oscilloscope 54. The pulse height selection of the display 9 as well as the x and y coordinates of the display are controlled by the position network 52 as is more fully described in the 11 Anger Patent No. 3,011,057 and the Muehllehner Patent No. ' 12 3,683,185.
13 In operation, the gamma rays 12 from the body 10 pass 14 through the holes 16 of the collimator 14 and impinge on the scintillator screen 2~, thereby producing a localized flash 16 of light. This flash of liyht causes the photocathode 42 to 17 produce a corresponding pattern of photoelectrons which are 18 accelerated to the output screen 46 by means of the electro-
22 Optically coupled to the exterior flat surface of the 23 output window 30 by means of light guides 48 are a plurality of 24 photo-multiplier tubes 50. These tubes, in turn, are connected to a triangulation and pulse height analyzing circuit 52. The 26 arrangement of the photo-multiplier tubes 50 and the circuitry of 2a 1 .l 31 . ., . , .. . . : . : . :
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1 the position locating or triangulation and pulse height analyzing 2 network 52 are well known to those skilled in the art and in 3 particular are described,with reference to Figure 2 in Anger 4 Patent No. 3,011,057 or with reference to Figures S and 6 of S Muehllehner Patent ~o. 3,683,185 and hence will not be described 6 in greater detail here. The output of the position network 7 52 is supplied to an appropriate display such as a cathode ray 8 tube oscilloscope 54. The pulse height selection of the display 9 as well as the x and y coordinates of the display are controlled by the position network 52 as is more fully described in the 11 Anger Patent No. 3,011,057 and the Muehllehner Patent No. ' 12 3,683,185.
13 In operation, the gamma rays 12 from the body 10 pass 14 through the holes 16 of the collimator 14 and impinge on the scintillator screen 2~, thereby producing a localized flash 16 of light. This flash of liyht causes the photocathode 42 to 17 produce a corresponding pattern of photoelectrons which are 18 accelerated to the output screen 46 by means of the electro-
19 static potential between the photocathode 42 and the output screen 46 which is supplied by the high voltage supply 44. The 21 accelerated photoelectrons which impinge on the phosphor out-22 put screen 46 produce corresponding light flashes on the '' 23 output screen which are detected'by the photo-multiplier tubes 24 50.
25 The parallel-hole collimator 14 can also be replaced for 26 certain applications by several other well-known types of 27 collimators such as: pin-hole, diverging hole, converging 28 hole, etc. Design considerations of these collimators are 29 also well known. See, for example, the following articles: "
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1) B. L. Keller, J. Nuc. Med. Vol 9, pages 233-235 (1968) "Optimum Dimensions of parallel-hole 3 multi-aperture collimators for Gamma-ray Cameras".
~ 2) H. O. Anger, "Radioisotope Cameras" in Instrumentation in Nuclear Medicine, ed. Gr. J. Hines (Academic 6 Press 1967) pages 485-552.
7 ~he design considerations of the light guide 48 are also 8 well known. See for example U. S. Patent Nos~.3,683,180 and 9 3,011,057.
As mentioned at the beginning of this description, the 11 use of the image intensifier structure between the photo-12 multiplier tubes 50 and the scintillator crystal 24 greatly 13 increases the number of photons produced with each incident ~ gamma ray thereby greatly increasing the ability of the tri-angulation network 52 to locate the centroid of the flash and l6 to further allow the network to better distinguish between 17 incident and scattered gamma rays by means of improved pulse 18 height statistics. The increase in the number of photons is 19 referred to as the pulse gain. The relationship between the pulse gain and image intensification tube v~ltage is shown 21 in Figure 2 for a tyPical combination of Sll (Cs-Sb) kind of 22 photocathode and P15 type of output phosphor.
23 For the same reason, the camera according to the invention 24 is able to operate satisfactorily at lower gamma ray energy levels than a conventional Anger camera, as is illustrated in 26 Figure 3. Thus, the camera of the invention greatly improves 27 the performance of a conventional Anger camera without intro-28 ducing any other disadvantages as most prior art systems do.
29 This improvement is obtained through the selection of a flat scintillator screen, a flat photocathode layer efficiently ., ... .
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, ~ lllg316' ~ ' 1 coupled to the scintillation 5creen, a flat output screen, 2 and an image intensification apparatus having extremely good 3 pulse height statistics.
Referrin~ now more particularly to Figure 5, a modified S embodiment of the camera of the invention is described. In 6 the conventional Anger camera as well as the modified and 7 improved Anger camera described above, the outputs from the 8 photo-multiplier tubes S0 are processed serially. This puts a 9 limitation on the response time of the camera. In order to increase the system count rate, and hence its response, the 11 scintillator screen 24, the photocathode 42, and the output 12 screen 46 can be segmented in corresponding and aligned 13 segments. The segmentation of the output screen is illustrated 14 in Figure 5 by tha reference numeral 46' and it is to be under-stood that the segmentations of the scintillator crystal 24 16 and the photocathode layer 42 are similarly segmented and 17 aligned. The photo-multiplier tubes 50 can be arranged in a 18 pattern as shown by the reference numeral 50' for each segment.
19 The triangulation network 52 is then arranged to process the outputs of the photo-multiplier tubes 50' serially only within 21 a given segment. The outputs from the tubes in the other 22 segments are also processed at the same time. The outputs from 23 the position network 52 may be sampled serially for purposes 24 of display or they may be supplied simultaneously to a multiple trace display. In this modification of the basic 26 gamma ray camera according to the invention, the segmentations 27 are optically partitionad to prevent cross-talk.
28 It is important to place the scintillator crystal 24 as 29 close to the collimator 14 as possible so that the high spatial 31 resolution of the camera can be utilized. A substantial space . ., -19- . :
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l I between the collimator and the input screen causes detioration 2 ¦ in the system's spatial resolution characteristics. The input 3 1 screen in the basic camera should be placed as close to the 4 ¦ input window 22 as possible without causing high voltage problems 1 due to too close a proximity. A better ~pproach, however, is 6 illustrated in Figure 6, in which a modified collimator 14' is 7 ¦ within the tube envelope 28, supported in the corona and 8 ¦ support ring 26' on the side of the scintillator crystal 24' 9 ¦ which faces the object lO. It should be noted that elements ¦ corresponding to those described above have been given the 11 corresponding reference numerals primed.
12Referring now more particularly to Figure 4, a modified 13 camera according to the, inventien which allows the usethe use 14 of low cost solid state photO-~ete~t:o~s i~ plac'e o'f th'~ pho'to-~
IS multiplier tubes 50, is illustrated. In this embodime~t, there 16 are two output phosphor display screens and two photocathodes.
17 Corresponding elements have been given the same numerals, 18 double primed. ' ' 19 The first output phosphor display screen 46'' is ~ounted ' on one face of a fiber-optic plate 54 which is suspended from 21 the tube envelope 28'' by means of insulators 56. On the 22 opposite face of the fiber-optic plate 54 a second photocathode 23 58 is deposited. The first and second photocathodes 46'' and 24 58 can be of the same material as described above for the primary embodiment of the invention. The fiber-optic plate 54 26 is oriented in a plane parallel to the first scintillator 27 crystal 24''.' 28A second output phosphor display screen 60 is deposited 29on the output window 30''. The power supply 44'' is connected "
30 between the first output phosphor display screen 46'' and the ..
, , ' X , -20--- !
' ~ )'' ' 1 first photocathode 42'' as wcll as between the second photo-2 cathode 58 and the second output phosphcr display screen 60.
3 The power supply is biased such that the potential between the ~ first photocathode screen 42'' and the first output display screen 46 " is approximately equal to the potential between the 6 second photocathode 58 and the second output display screen 60.
7 The potential between the first photocathode and the second 8 output phosphor display screen 60 is double these intermediate 9 potentials. The first output display screen 46'' and the second photocathode 58 are connected together to have the same 11 potential.:
12 In place of the photo-multiplier tubes at the output l3 display screen is an array of solid state detectors 62 which 1~ ~r~ coupled to a position network 52 ". These solid st~t:e IS detectors scnse the light output image at the second output l6 display screen in the same way that the photo-multiplier tubes 17 operated in the embodiment depicted in Figure 1. See for 18 example U. S. Patent No. 3,683,185 ~Muehllehner). The output 19 from the position network 52'' is supplied to an appropriate display as in the primary embodiment. Appropriate light guide 21 48'' is placed between the detector array 52 and the output 22 window 46''. The great advantage offered by the two stages 23 of amplification in this e~bodiment is the use of the simpler 2~ solid state detectors in place of the photo-multiplier tubes.
2S These solid state detectors are simpler, more stable and far 26 less expensive than the photo-multiplier tubes.
27 Another embodiment is a converging array of light guides 28 48''',as shown in Figure 10, coupling to the above described 29 Z-stage tube on one end and on the other end to a smaller array of solid state detectors. For more efficient transfer of '. ' ~ '''' - ~v ~ 931~ ~
1 light, each light guide may be claded with low index of 2 refraction material.
3 From the foregoing description, it can be seen that the 4 conventional Anger camera has been modified by the applicant's interposition of a proximity type image intensifier tube 6 between the scintillator screen and the photo-detector network 7 so that the camera can operate at better spatial resolution 8 and with better scatter rejection at lower gamma ray energy 9 ranges.
It should also be pointed out that there has here-to-fore been a common misconception about the one-to-one type of 12 image size image intensifier approach taken in the present 13 invention. That is the concept of gain. Normally, the gain 14 of a tube is defined by the brightness gain which is the product of the true electronic gain of the tube and the gain 16 obtained through minification of the output image. Since a 17 one-to-one type image intensifier tube does not minify the 18 output image, its brightness gain is the same as the true 19 electronic gain, whereas an electrostatic inverter type of tube with a lOX minified output image would have a brightness 21 gain lOOX higher than that of the one-to-one type. However, 22 in applications where pulse counting and sensing are used, 23 only the true electronic gain is of value. Gain obtained 24 through minified output is of no value. Thus, the false fear of not enough gain in a one-to-one design discouraged prior 26 attempts of the foregoing approach.
27 While in the above description it has been assumed that 28 the incident radiation are gamma rays in other less preferred 29 embodiments the radiation can be other types of nuclear radiation such as protons. ., ! ' .: ~
-;C';~3 ' . .
1 ¦ The terms and expressions which have been employed here 2 ¦ are used as terms of description and not of limitation, and 3 ¦ there is no intention, in the use of such terms and expressions, 4 ¦ of excluding equivalents of the features shown and described, ¦ or portions thereof, it being recognized that various modifi-¦ catlons are possi le within the scope cf the ~nv~ntion cl imed.
~4 22 . .
28 .
29 . . .
32 I .
. .
. : , ', , :
' `
25 The parallel-hole collimator 14 can also be replaced for 26 certain applications by several other well-known types of 27 collimators such as: pin-hole, diverging hole, converging 28 hole, etc. Design considerations of these collimators are 29 also well known. See, for example, the following articles: "
~, '~ -17- ' , ' ' , ' ,:
, . .
.
~ 1119316 ~
1) B. L. Keller, J. Nuc. Med. Vol 9, pages 233-235 (1968) "Optimum Dimensions of parallel-hole 3 multi-aperture collimators for Gamma-ray Cameras".
~ 2) H. O. Anger, "Radioisotope Cameras" in Instrumentation in Nuclear Medicine, ed. Gr. J. Hines (Academic 6 Press 1967) pages 485-552.
7 ~he design considerations of the light guide 48 are also 8 well known. See for example U. S. Patent Nos~.3,683,180 and 9 3,011,057.
As mentioned at the beginning of this description, the 11 use of the image intensifier structure between the photo-12 multiplier tubes 50 and the scintillator crystal 24 greatly 13 increases the number of photons produced with each incident ~ gamma ray thereby greatly increasing the ability of the tri-angulation network 52 to locate the centroid of the flash and l6 to further allow the network to better distinguish between 17 incident and scattered gamma rays by means of improved pulse 18 height statistics. The increase in the number of photons is 19 referred to as the pulse gain. The relationship between the pulse gain and image intensification tube v~ltage is shown 21 in Figure 2 for a tyPical combination of Sll (Cs-Sb) kind of 22 photocathode and P15 type of output phosphor.
23 For the same reason, the camera according to the invention 24 is able to operate satisfactorily at lower gamma ray energy levels than a conventional Anger camera, as is illustrated in 26 Figure 3. Thus, the camera of the invention greatly improves 27 the performance of a conventional Anger camera without intro-28 ducing any other disadvantages as most prior art systems do.
29 This improvement is obtained through the selection of a flat scintillator screen, a flat photocathode layer efficiently ., ... .
: . . , , ~ .:
, ~ lllg316' ~ ' 1 coupled to the scintillation 5creen, a flat output screen, 2 and an image intensification apparatus having extremely good 3 pulse height statistics.
Referrin~ now more particularly to Figure 5, a modified S embodiment of the camera of the invention is described. In 6 the conventional Anger camera as well as the modified and 7 improved Anger camera described above, the outputs from the 8 photo-multiplier tubes S0 are processed serially. This puts a 9 limitation on the response time of the camera. In order to increase the system count rate, and hence its response, the 11 scintillator screen 24, the photocathode 42, and the output 12 screen 46 can be segmented in corresponding and aligned 13 segments. The segmentation of the output screen is illustrated 14 in Figure 5 by tha reference numeral 46' and it is to be under-stood that the segmentations of the scintillator crystal 24 16 and the photocathode layer 42 are similarly segmented and 17 aligned. The photo-multiplier tubes 50 can be arranged in a 18 pattern as shown by the reference numeral 50' for each segment.
19 The triangulation network 52 is then arranged to process the outputs of the photo-multiplier tubes 50' serially only within 21 a given segment. The outputs from the tubes in the other 22 segments are also processed at the same time. The outputs from 23 the position network 52 may be sampled serially for purposes 24 of display or they may be supplied simultaneously to a multiple trace display. In this modification of the basic 26 gamma ray camera according to the invention, the segmentations 27 are optically partitionad to prevent cross-talk.
28 It is important to place the scintillator crystal 24 as 29 close to the collimator 14 as possible so that the high spatial 31 resolution of the camera can be utilized. A substantial space . ., -19- . :
' `, ' ~ ~119316 ~
I
. . .
d~ t~ r ~
l I between the collimator and the input screen causes detioration 2 ¦ in the system's spatial resolution characteristics. The input 3 1 screen in the basic camera should be placed as close to the 4 ¦ input window 22 as possible without causing high voltage problems 1 due to too close a proximity. A better ~pproach, however, is 6 illustrated in Figure 6, in which a modified collimator 14' is 7 ¦ within the tube envelope 28, supported in the corona and 8 ¦ support ring 26' on the side of the scintillator crystal 24' 9 ¦ which faces the object lO. It should be noted that elements ¦ corresponding to those described above have been given the 11 corresponding reference numerals primed.
12Referring now more particularly to Figure 4, a modified 13 camera according to the, inventien which allows the usethe use 14 of low cost solid state photO-~ete~t:o~s i~ plac'e o'f th'~ pho'to-~
IS multiplier tubes 50, is illustrated. In this embodime~t, there 16 are two output phosphor display screens and two photocathodes.
17 Corresponding elements have been given the same numerals, 18 double primed. ' ' 19 The first output phosphor display screen 46'' is ~ounted ' on one face of a fiber-optic plate 54 which is suspended from 21 the tube envelope 28'' by means of insulators 56. On the 22 opposite face of the fiber-optic plate 54 a second photocathode 23 58 is deposited. The first and second photocathodes 46'' and 24 58 can be of the same material as described above for the primary embodiment of the invention. The fiber-optic plate 54 26 is oriented in a plane parallel to the first scintillator 27 crystal 24''.' 28A second output phosphor display screen 60 is deposited 29on the output window 30''. The power supply 44'' is connected "
30 between the first output phosphor display screen 46'' and the ..
, , ' X , -20--- !
' ~ )'' ' 1 first photocathode 42'' as wcll as between the second photo-2 cathode 58 and the second output phosphcr display screen 60.
3 The power supply is biased such that the potential between the ~ first photocathode screen 42'' and the first output display screen 46 " is approximately equal to the potential between the 6 second photocathode 58 and the second output display screen 60.
7 The potential between the first photocathode and the second 8 output phosphor display screen 60 is double these intermediate 9 potentials. The first output display screen 46'' and the second photocathode 58 are connected together to have the same 11 potential.:
12 In place of the photo-multiplier tubes at the output l3 display screen is an array of solid state detectors 62 which 1~ ~r~ coupled to a position network 52 ". These solid st~t:e IS detectors scnse the light output image at the second output l6 display screen in the same way that the photo-multiplier tubes 17 operated in the embodiment depicted in Figure 1. See for 18 example U. S. Patent No. 3,683,185 ~Muehllehner). The output 19 from the position network 52'' is supplied to an appropriate display as in the primary embodiment. Appropriate light guide 21 48'' is placed between the detector array 52 and the output 22 window 46''. The great advantage offered by the two stages 23 of amplification in this e~bodiment is the use of the simpler 2~ solid state detectors in place of the photo-multiplier tubes.
2S These solid state detectors are simpler, more stable and far 26 less expensive than the photo-multiplier tubes.
27 Another embodiment is a converging array of light guides 28 48''',as shown in Figure 10, coupling to the above described 29 Z-stage tube on one end and on the other end to a smaller array of solid state detectors. For more efficient transfer of '. ' ~ '''' - ~v ~ 931~ ~
1 light, each light guide may be claded with low index of 2 refraction material.
3 From the foregoing description, it can be seen that the 4 conventional Anger camera has been modified by the applicant's interposition of a proximity type image intensifier tube 6 between the scintillator screen and the photo-detector network 7 so that the camera can operate at better spatial resolution 8 and with better scatter rejection at lower gamma ray energy 9 ranges.
It should also be pointed out that there has here-to-fore been a common misconception about the one-to-one type of 12 image size image intensifier approach taken in the present 13 invention. That is the concept of gain. Normally, the gain 14 of a tube is defined by the brightness gain which is the product of the true electronic gain of the tube and the gain 16 obtained through minification of the output image. Since a 17 one-to-one type image intensifier tube does not minify the 18 output image, its brightness gain is the same as the true 19 electronic gain, whereas an electrostatic inverter type of tube with a lOX minified output image would have a brightness 21 gain lOOX higher than that of the one-to-one type. However, 22 in applications where pulse counting and sensing are used, 23 only the true electronic gain is of value. Gain obtained 24 through minified output is of no value. Thus, the false fear of not enough gain in a one-to-one design discouraged prior 26 attempts of the foregoing approach.
27 While in the above description it has been assumed that 28 the incident radiation are gamma rays in other less preferred 29 embodiments the radiation can be other types of nuclear radiation such as protons. ., ! ' .: ~
-;C';~3 ' . .
1 ¦ The terms and expressions which have been employed here 2 ¦ are used as terms of description and not of limitation, and 3 ¦ there is no intention, in the use of such terms and expressions, 4 ¦ of excluding equivalents of the features shown and described, ¦ or portions thereof, it being recognized that various modifi-¦ catlons are possi le within the scope cf the ~nv~ntion cl imed.
~4 22 . .
28 .
29 . . .
32 I .
. .
. : , ', , :
' `
Claims (19)
1. An improved scintillation camera of the type having a radiation collimator, scintillator means aligned with the collimator for converting radiation passing through the collimator and impinging upon the scintillator means into a corresponding light pattern, the scintillator means including a scintillator screen and an output screen for displaying the light patterns, a plurality of photo-electric detectors disposed in view of substantially co-extensive portions of the output screen, and means connected to the photo-electric detectors for receiving signals emitted from them and for translating such signals into relatively displaced images of said light patterns, wherein the improvement resides in the scintillator means which comprise:
a flat scintillator screen, a first flat photocathode disposed with its flat sur-faces parallel to and adjacent to the scintillator screen, a first flat output phosphor display screen which consti-tutes the light output screen of the scintillator means, the display screen having its flat surfaces parallel to and spaced apart from the flat surfaces of the photocathode and on its side opposite from the scintillator screen, an output window on which the display screen is mounted, a metallic input window, means for applying an accelerating electrostatic potential between the display screen and the photocathode, and an open ended, hollow, evacuated envelope surrounding the scintillator screen and the photocathode and which is closed at one end by the output window and at the other end by the input window.
a flat scintillator screen, a first flat photocathode disposed with its flat sur-faces parallel to and adjacent to the scintillator screen, a first flat output phosphor display screen which consti-tutes the light output screen of the scintillator means, the display screen having its flat surfaces parallel to and spaced apart from the flat surfaces of the photocathode and on its side opposite from the scintillator screen, an output window on which the display screen is mounted, a metallic input window, means for applying an accelerating electrostatic potential between the display screen and the photocathode, and an open ended, hollow, evacuated envelope surrounding the scintillator screen and the photocathode and which is closed at one end by the output window and at the other end by the input window.
2. An improved scintillation camera as recited in Claim l wherein the envelope is metal and the electrostatic potential means supply a high negative potential to the scintillator screen and photocathode and a ground potential to the output display screen and the envelope.
3. An improved scintillation camera as recited in Claim l wherein the scintillation screen, the photocathode and the output display screen have substantially the same diagonal dimensions.
4. An improved scintillation camera as recited in Claim 1 further comprising separate, converging light guides for coupling the photo-electric detectors to the output window.
5. An improved scintillation camera as recited in Claim 1 wherein the input window is concave inwardly with respect to the tube envelope and is made from type 17-7 PH stainless steel.
6. An improved scintillation camera as recited in Claim 1 wherein the scintillator screen is a scintillator crystal and further comprising a thin layer of light transmitting material interposed between the photocathode and the scintillator crystal which material has an index of refraction which matches the index of refraction of the scintillator crystal.
7. An improved scintillation camera as recited in Claim 6 wherein the thin layer is comprised of freshly vapor deposited CsI.
8. An improved scintillation camera as recited in Claim 6 wherein the thin layer is comprised of freshly vapor deposited CsI(Na).
9. An improved scintillation camera as recited in Claim 6 wherein the thin layer is comprised of Al2O3.
10. An improved scintillation camera as recited in Claim 1 further comprising a fiber optic plate, a second photocathode and a second output phosphor display screen and wherein the first output display screen is mounted on one side of the fiber optic plate and the second photocathode is mounted on the other side of the fiber optic plate, the second output display screen being spaced apart from the second photocathode and plane parallel to it, means for applying an accelerating electrostatic potential between the second photocathode and the second output display screen and wherein the second photocathode, the fiber optic plate and the second output display screen are contained within the tube envelope.
11. An improved scintillation camera as recited in Claim 1 wherein the scintillator screen, the first photocathode, the first output display screen and the output window are divided into optically isolated segments and wherein the signal trans-lating means connected to the photo-detectors of different segments are operated simultaneously.
12. An improved scintillation camera as recited in Claim 1 wherein the collimator is mounted within the tube envelope and adjacent to the scintillator screen.
13. A scintillation camera comprising a radiation collimator, a flat scintillator screen aligned with the collimator for converting radiation passing through the collimator and impinging upon the scintillator screen into a corresponding light pattern, a first flat photocathode disposed with its flat sur-faces parallel to and adjacent to the scintillator screen for converting the light patterns on the scintillator screen into corresponding patterns of emitted photo-electrons, a first flat output phosphor display screen, the display screen having its flat surfaces parallel to and spaced apart from the flat surfaces of the photocathode and on its side opposite from the scintillator screen, the scintillator screen, the photocathode and the output phosphor display screen all having the same diagonal dimensions, an output window on which the display screen is mounted, means for applying an accelerating, negative electro-static potential between the photocathode and the display screen to accelerate the photo-electrons emitted by the photocathode toward the output phosphor display screen where they impinge upon it and produce corresponding, intensified light patterns, a plurality of photo-electric detectors disposed in view of substantially co-extensive portions of the output screen, and means connected to the photo-electric detectors for receiving signals emitted from them and for translating such signals into relatively displaced images of said light patterns.
a metallic input window, and an open ended, hollow, evacuated metallic tube envelope surrounding the scintillator screen and the photocathode and which is closed at one end by the output window and at the other end by the input window.
a metallic input window, and an open ended, hollow, evacuated metallic tube envelope surrounding the scintillator screen and the photocathode and which is closed at one end by the output window and at the other end by the input window.
14. A scintillation camera as recited in Claim 13 wherein the input window is concave inwardly with respect to the tube envelope and is made from type 17-7 PH stainless steel.
15. A scintillation camera as recited in Claim 13 further comprising a fiber optic plate, a second photocathode and a second output phosphor display screen and wherein the first output display screen is mounted on one side of the fiber optic plate and the second photocathode is mounted on the other side of the fiber optic plate, the second output display screen being spaced apart from the second photocathode and plane parallel to it, means for applying an accelerating electrostatic potential between the second photocathode and the second output display screen and wherein the second photocathode, the fiber optic plate and the second output display screen are contained within the tube envelope.
16. A scintillation camera as recited in Claim 13 wherein the scintillator screen, the first photocathode, the first output display screen and the output window are divided into optically isolated segments and wherein the signal trans-lating means connected to the photo-detectors of different segments are operated simultaneously.
17. A scintillation camera as recited in Claim 13 wherein the collimator is mounted within the tube envelope and adjacent to the scintillator screen.
18. A scintillation camera as recited in Claim 13 wherein the scintillator screen is a scintillator crystal selected from the group consisting essentially of CsI(Na) or NaI(Tl) and further comprising a barrier layer interposed between the scintillator crystal and the photocathode, the barrier layer being transparent and having an index of refraction which matches the index of refraction of the scintillator crystal.
19. A scintillation camera as recited in Claim 18 wherein the barrier layer is made of a material selected from the group consisting essentially of CsI(Na), CsI, BGO, or Al2O3.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US885,169 | 1978-03-10 | ||
| US05/885,169 US4221967A (en) | 1978-03-10 | 1978-03-10 | Gamma ray camera |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119316A true CA1119316A (en) | 1982-03-02 |
Family
ID=25386309
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000323047A Expired CA1119316A (en) | 1978-03-10 | 1979-03-09 | Gamma ray camera |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4221967A (en) |
| JP (2) | JPS54127275A (en) |
| CA (1) | CA1119316A (en) |
| DE (2) | DE2909143A1 (en) |
| FR (2) | FR2419583A1 (en) |
| GB (2) | GB2016206B (en) |
| NL (1) | NL7901908A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3004351A1 (en) * | 1980-02-06 | 1981-08-13 | Siemens AG, 1000 Berlin und 8000 München | MULTI-STAGE VACUUM X-RAY IMAGE AMPLIFIER |
| FR2481466A1 (en) * | 1980-04-29 | 1981-10-30 | Labo Electronique Physique | SCINTILLATION CAMERA WITH LOCATOR HAVING A SCINTILLATION INTENSIFIER |
| US4454422A (en) * | 1982-01-27 | 1984-06-12 | Siemens Gammasonics, Inc. | Radiation detector assembly for generating a two-dimensional image |
| US4523091A (en) * | 1982-03-22 | 1985-06-11 | Siemens Gammasonics, Inc. | Radiation detecting apparatus with reduced magnetic field sensitivity |
| GB2208256B (en) * | 1983-04-15 | 1989-07-26 | Philips Electronic Associated | Infra-red radiation imaging devices and systems |
| US4550251A (en) * | 1983-07-08 | 1985-10-29 | Varian Associates, Inc. | Image intensifier tube with increased contrast ratio |
| GB8701648D0 (en) * | 1987-01-26 | 1987-03-04 | Pillay M | Filter for gamma-ray camera |
| JPH0219259A (en) * | 1988-07-05 | 1990-01-23 | Yamarura Glass Co Ltd | Synthetic resin cover |
| US5229613A (en) * | 1991-09-06 | 1993-07-20 | Horiba Instruments, Incorporated | Extended lifetime scintillation camera plate assembly |
| FR2700889B1 (en) † | 1993-01-22 | 1995-02-24 | Thomson Tubes Electroniques | Image converter tube, and method for suppressing stray light in this tube. |
| JPH0998970A (en) * | 1995-10-06 | 1997-04-15 | Canon Inc | X-ray photographing equipment |
| AU3958799A (en) * | 1998-06-01 | 1999-12-20 | Hamamatsu Photonics K.K. | Photomultiplier and radiation sensor |
| US6671541B2 (en) * | 2000-12-01 | 2003-12-30 | Neomed Technologies, Inc. | Cardiovascular imaging and functional analysis system |
| EP1478945A2 (en) * | 2002-02-01 | 2004-11-24 | Board Of Regents The University Of Texas System | A production method for making position-sensitive radiation detector arrays |
| EP2212902A4 (en) | 2007-11-01 | 2016-12-07 | Rapiscan Systems Inc | Multiple screen detection systems |
| KR20110068070A (en) * | 2009-12-15 | 2011-06-22 | 삼성전기주식회사 | Imaging device for low-luminance using silicon photomultiplier devices |
| US9291723B2 (en) * | 2013-06-27 | 2016-03-22 | Savannah River Nuclear Solutions, Llc | Instrument for assaying radiation |
| US10866329B2 (en) * | 2016-06-29 | 2020-12-15 | Siemens Medical Solutions Usa, Inc. | System and method to unpile overlapping pulses |
| US9945963B1 (en) | 2017-08-01 | 2018-04-17 | Siemens Medical Solutions Usa, Inc. | Dynamic control of event dumping |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR916994A (en) * | 1945-07-06 | 1946-12-20 | Radiologie Cie Gle | Device for increasing the light output of fluorescent hundred x-ray screens |
| US2739258A (en) * | 1950-05-19 | 1956-03-20 | Edward E Sheldon | System of intensification of x-ray images |
| US3011057A (en) * | 1958-01-02 | 1961-11-28 | Hal O Anger | Radiation image device |
| GB1120393A (en) * | 1965-05-06 | 1968-07-17 | Cole E K Ltd | Improvements in or relating to radiation detectors |
| US3558893A (en) * | 1967-01-30 | 1971-01-26 | Picker Corp | X- and gamma-ray sensitive image intensification tube |
| US3531651A (en) * | 1967-12-21 | 1970-09-29 | Varian Associates | Gamma-ray camera employing an electro-optic bypass for energy selection |
| US3683180A (en) * | 1969-06-16 | 1972-08-08 | Picker Corp | Scintillation camera with removable subassembly |
| US3683185A (en) * | 1969-08-08 | 1972-08-08 | Nuclear Chicago Corp | Radiation imaging apparatus |
| US3719823A (en) * | 1969-08-20 | 1973-03-06 | E Sheldon | Radio-isotope cameras using vacuum tubes with fiberoptic endwalls and luminiscent means of fiberoptic construction |
| BE759730R (en) * | 1969-12-03 | 1971-05-17 | Ekco Instr Ltd | INDICATOR OR DETECTOR DEVICE FOR NUCLEAR RADIATION, SUCH AS RAYS |
| BE786084A (en) * | 1971-07-10 | 1973-01-10 | Philips Nv | LUMINESCENT SCREEN WITH MOSAIC STRUCTURE |
| DE2151079A1 (en) * | 1971-10-13 | 1973-04-19 | Siemens Ag | RADIATION WINDOW |
| US3749920A (en) * | 1971-12-03 | 1973-07-31 | E Sheldon | System for x-ray image intensification |
| US3829688A (en) * | 1972-05-04 | 1974-08-13 | Raytheon Co | High intensity radiation imaging system |
| US3838273A (en) * | 1972-05-30 | 1974-09-24 | Gen Electric | X-ray image intensifier input |
| US3911278A (en) * | 1972-07-05 | 1975-10-07 | Ohio Nuclear | Radiation sensing device |
| US3890506A (en) * | 1973-11-15 | 1975-06-17 | Gen Electric | Fast response time image tube camera |
| US3989890A (en) * | 1974-02-14 | 1976-11-02 | Westinghouse Electric Corporation | Optical imaging system utilizing a light valve array and a coupled photoemissive target |
| FR2366689A1 (en) * | 1975-12-31 | 1978-04-28 | Thomson Csf | NEW PULSE VISUALIZATION CHAIN USING PHOTON AND ELECTRON CONVERSIONS |
| FR2352346A1 (en) * | 1976-05-18 | 1977-12-16 | Thomson Csf | NEW SCINTIGRAPHY SHOOTING SET |
| DE2750132A1 (en) * | 1976-11-12 | 1978-05-18 | Diagnostic Inform | X-RAY SENSITIVE IMAGE AMPLIFIER TUBE AND RADIOGRAPHIC CAMERA EQUIPPED WITH IT |
| JPS5372673A (en) * | 1976-12-10 | 1978-06-28 | Aloka Co Ltd | Radiation distribution detector using afterglow scintillator |
| US4104516A (en) * | 1977-01-28 | 1978-08-01 | Diagnostic Information Inc. | Direct view, panel type x-ray image intensifier tube |
-
1978
- 1978-03-10 US US05/885,169 patent/US4221967A/en not_active Expired - Lifetime
-
1979
- 1979-03-08 DE DE19792909143 patent/DE2909143A1/en not_active Ceased
- 1979-03-08 DE DE2909066A patent/DE2909066A1/en active Granted
- 1979-03-09 GB GB7908432A patent/GB2016206B/en not_active Expired
- 1979-03-09 JP JP2817779A patent/JPS54127275A/en active Granted
- 1979-03-09 GB GB7908431A patent/GB2016205B/en not_active Expired
- 1979-03-09 JP JP2817679A patent/JPS54126582A/en active Pending
- 1979-03-09 FR FR7906129A patent/FR2419583A1/en active Granted
- 1979-03-09 NL NL7901908A patent/NL7901908A/en not_active Application Discontinuation
- 1979-03-09 FR FR7906128A patent/FR2419522A1/en active Granted
- 1979-03-09 CA CA000323047A patent/CA1119316A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS54127275A (en) | 1979-10-03 |
| DE2909143A1 (en) | 1979-09-13 |
| GB2016205B (en) | 1982-12-22 |
| NL7901908A (en) | 1979-09-12 |
| GB2016206A (en) | 1979-09-19 |
| JPS54126582A (en) | 1979-10-01 |
| GB2016205A (en) | 1979-09-19 |
| JPS6340351B2 (en) | 1988-08-10 |
| FR2419583B1 (en) | 1984-02-24 |
| GB2016206B (en) | 1982-10-06 |
| FR2419522B1 (en) | 1984-08-24 |
| FR2419583A1 (en) | 1979-10-05 |
| FR2419522A1 (en) | 1979-10-05 |
| US4221967A (en) | 1980-09-09 |
| DE2909066C2 (en) | 1988-01-07 |
| DE2909066A1 (en) | 1979-09-20 |
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