US3793519A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gamma camera activated to be responsive to selected levels of light emission
Assignee: National Research Development Corp UK
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Filing: 1972-04-13
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Granted: 1974-02-19
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Expires: 1992-04-13
Abstract
Abstract The invention concerns apparatus for use in investigating the distribution of radiation from an extended source of ionising rays and is particularly concerned with gamma cameras for sensing Gamma radiation. In normal Gamma cameras, due to the long exposure time, the sensitivity of the camera is reduced by spurious light emission from the scintillation screen. In the present invention the effect of this spurious emission is reduced by only triggering the image intensifier in response to predetermined values of light emission. This predetermined triggering is achieved by collecting the unwanted light emitted at the edges of the scintillation screen and directing this into one or more photomultipliers, the outputs of which are taken to a pulse height analyser which is used to trigger the image intensifier.
Inventors
- 👤 J Mallard
- 👤 Mitchell J Gault
- 👤 R Wilks
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 16:24
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/161; G01T1/164; G01T1/1641; G01T1/1645
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
116 words
A device for investigating the distribution of radiation from an extended source of ionising rays, including a scintillation screen which emits visible light when bombarded by the radiation, a lens system for focusing light emitted from the main parallel faces of the scintillation screen on to an image intensifying device, means for collecting at the periphery of the scintillation screen light totally internally reflected from the main faces of the scintillation screen and for directing such collected light into at least one photomultiplier, and means reSponsive to the output of the photomultiplier for switching the image intensifier on so that the latter is operated only in response to a predetermined amount of radiation reaching the photomultiplier.
Claim 2
Independent Claim
116 words
A device for investigating the distribution of radiation from an extended source of ionising rays, including a scintillation screen which emits visible light when bombarded by the radiation, a lens system for focusing light emitted from the main parallel faces of the scintillation screen on to an image intensifying device, means for collecting at the periphery of the scintillation screen light totally internally reflected from the main faces of the scintillation screen and for directing such collected light into at least one photomultiplier, and means reSponsive to the output of the photomultiplier for switching the image intensifier on so that the latter is operated only in response to a predetermined amount of radiation reaching the photomultiplier.
Claim 3
Dependent Claim
25 words
A device as claimed in claim 1 wherein the means for collecting the light comprises a translucent body surrounding the periphery of the scintillation screen.
Claim 4
Dependent Claim
39 words
A device as claimed in claim 2 wherein the translucent body has a frustoconical surface including a plurality of said photomultiplier devices, at which light collected from the scintillation screen is totally internally reflected to each of the photomultipliers.
Claim 5
Dependent Claim
28 words
A device as claimed in claim 3 in which a high refractive index coupling fluid is interposed in the gaps between the scintillation screen and the translucent body.
Claim 6
Dependent Claim
24 words
A device as claimed in claim 4 in which the or each photomultiplier has at least its cathode partially embedded in said translucent body.
Claim 7
Dependent Claim
128 words
A gamma camera for investigating distribution of gamma radiation from an extended source comprising a collimator mounted parallel to a crystal scintillation screen, a lens system for focusing light emitted from the scintillation screen on to an image intensifying device, a translucent body surrounding the scintillation screen so as to collect at the periphery of the scintillation screen light totally internally reflected from the main faces of the scintillation screen, said translucent body having a frustoconical surface including at least one photomultiplier device disposed therein, for totally internally reflecting the collected light into said photomultiplier, and means responsive to the output of the photomultiplier for switching the image intensifier on so that the latter is operated only in response to a predetermined amount of radiation reaching the photomultiplier.
Claim 8
Dependent Claim
128 words
A gamma camera for investigating distribution of gamma radiation from an extended source comprising a collimator mounted parallel to a crystal scintillation screen, a lens system for focusing light emitted from the scintillation screen on to an image intensifying device, a translucent body surrounding the scintillation screen so as to collect at the periphery of the scintillation screen light totally internally reflected from the main faces of the scintillation screen, said translucent body having a frustoconical surface including at least one photomultiplier device disposed therein, for totally internally reflecting the collected light into said photomultiplier, and means responsive to the output of the photomultiplier for switching the image intensifier on so that the latter is operated only in response to a predetermined amount of radiation reaching the photomultiplier.
Claim 9
Dependent Claim
65 words
A gamma camera as claimed in Claim 6 and including a plurality of said photomultiplier devices, means for summing the outputs of the photomultipliers, a pulse height analyser for analysing the height of the summed output of the photomultipliers, and switching means triggered by the pulse height analyser for switching the image intensifier on whenever the summed output of the photomultipliers exceeds a predetermined value.
Claim 10
Dependent Claim
35 words
A gamma camera as claimed in claim 7 and including a plate of lead glass parallel to the scintillation crystal and located on the side of the scintillation crystal remote from the incoming gamma rays.
Claim 11
Dependent Claim
23 words
A gamma camera as claimed in claim 8 and including a fibre optic system for coupling the lens system to said image intensifier.
Claim 12
Dependent Claim
22 words
A gamma camera as claimed in claim 9 wherein at least the cathodes of the photomultipliers are embedded in the translucent body.
Claim 13
Dependent Claim
20 words
A gamma camera as claimed in claim 7 wherein the summed output is a total of all the phtomultiplier outputs.
Claim 14
Dependent Claim
28 words
A gamma camera as claimed in claim 7 wherein the pulse height analyser produces an output when the summed output of the photomultiplier exceeds a selected average value.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-18 | 1977-08-20 | 1978-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-18 | 1981-08-20 | 1982-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-18 | 1985-08-20 | 1986-02-19 | $7700.00 | Window Closed / Lapsed |