US5449897A
Expired / Lapsed
US
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Automatic gain calibration for gamma camera system
Assignee: Koninklijke Philips NV
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Filing: 1994-10-03
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Granted: 1995-09-12
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Expires: 2014-10-03
Abstract
Abstract An automatic gain calibration system for photomultipliers of a scintillation detector operable during periods when a collimator is installed to the scintillation detector. The system provides for calibration of the photomultipliers (PMTs) that are located along the periphery of the detector whose surfaces that are partially or totally obscured by the solid lead edge regions of the installed collimator (e.g., obscured PMTs). In such a manner, the entire scintillation detector may be calibrated effectively without removal of the heavy and awkwardly handled collimator. The automatic calibration system adjusts the preamplification gain associated with each channel of the PMT array to maintain the effective gain of each PMT in response to long term variations in the characteristic gain of each PMT. For calibration, the system measures the response of an obscured PMT to gamma events occurring within a thin strip area that extends into the central portion of the collimator. There is a separate strip area for each obscured tube. The preamplification gain of an obscured tube is then calibrated, when the collimator is installed, based on a recorded value of an originally calibrated response of the obscured PMT for gamma events within this strip area.
Inventors
- 👤 Hugo Bertelsen
- 👤 Horace H. Hines
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 01:50
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/161; G01T1/164; G01T1/1641; G01T1/1642; G01T1/1647; G01T1/20; G01T1/208; G01T1/36; G01T1/40
Claims Analysis
Total Claims: 39
Claim 1
Independent Claim
140 words
In a gamma camera system having a scintillation detector with a photomultiplier array and a collimator, wherein each photomultiplier generates a channel signal, an apparatus for automatically calibrating gains associated with individual channel signals while said collimator is installed, said apparatus comprising: a processor for defining a strip area associated with an obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; said processor for recording a set of responses of said obscured photomultiplier for a sample of gamma events detected within said strip area; said processor for determining a representative response of said set of responses; and said processor for automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a predetermined and stored reference response of said obscured photomultiplier and (2) said representative response of said obscured photomultiplier.
Claim 2
Dependent Claim
140 words
In a gamma camera system having a scintillation detector with a photomultiplier array and a collimator, wherein each photomultiplier generates a channel signal, an apparatus for automatically calibrating gains associated with individual channel signals while said collimator is installed, said apparatus comprising: a processor for defining a strip area associated with an obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; said processor for recording a set of responses of said obscured photomultiplier for a sample of gamma events detected within said strip area; said processor for determining a representative response of said set of responses; and said processor for automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a predetermined and stored reference response of said obscured photomultiplier and (2) said representative response of said obscured photomultiplier.
Claim 3
Dependent Claim
28 words
A gain calibration apparatus as described in claim 1 wherein said stored reference response of said obscured photomultiplier is responsive to gamma events detected within said strip area.
Claim 4
Dependent Claim
42 words
A gain calibration apparatus as described in claim 2 wherein said installed collimator comprises a first region obscuring gamma ray passage and a second region allowing passage of collimated gamma rays and wherein said obscured photomultiplier is aligned with said first region.
Claim 5
Dependent Claim
22 words
A gain calibration apparatus as described in claim 3 wherein said strip region is aligned with said second region of said collimator.
Claim 6
Dependent Claim
29 words
A gain calibration apparatus as described in claim 4 wherein said strip area is an arc shaped narrow two dimensional area centered about the center of said obscured photomultiplier.
Claim 7
Dependent Claim
47 words
A gain calibration apparatus as described in claim 4 further comprising controlled gain circuitry coupled to a channel signal generated by said obscured photomultiplier, said controlled gain circuitry for applying said preamplification gain to said channel signal, wherein said controlled gain circuitry is responsive to said processor.
Claim 8
Dependent Claim
53 words
A gain calibration apparatus as described in claim 3 wherein said processor is further for determining a first response of said obscured photomultiplier at initial calibration of said scintillation detector based on gamma events occurring within said strip area when said collimator is removed, wherein said first response is said stored reference response.
Claim 9
Dependent Claim
113 words
A gain calibration apparatus as described in claim 7 wherein said processor defines a central area associated with a central photomultiplier of said photomultiplier array wherein said central area is located above the surface of said central photomultiplier; said processor for recording a set of responses of said central photomultiplier for a sample of gamma events detected within said central area; said processor for determining a representative response of said set of responses of said central photomultiplier; and said processor for automatically adjusting a preamplification gain associated with said central photomultiplier based on (1) a predetermined and stored reference response of said central photomultiplier and (2) said representative response of said central photomultiplier.
Claim 10
Dependent Claim
22 words
A gain calibration apparatus as described in claim 8 wherein said central photomultiplier is aligned with said second region of said collimator.
Claim 11
Dependent Claim
152 words
In a gamma camera system having a scintillation detector with a photomultiplier array and a collimator, wherein each photomultiplier generates a channel signal, an apparatus for automatically calibrating gains associated with individual channel signals while said collimator is installed, said apparatus comprising: a processor for defining a strip area associated with an obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; said processor for recording a set of total energy signals of said photomultiplier array for a sample of gamma events detected within said strip area of said obscured photomultiplier; said processor for determining a representative total energy signal of said set of total energy signals; and said processor for automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a stored reference total energy signal for gamma events occurring within said strip area and (2) said representative total energy signal.
Claim 12
Dependent Claim
152 words
In a gamma camera system having a scintillation detector with a photomultiplier array and a collimator, wherein each photomultiplier generates a channel signal, an apparatus for automatically calibrating gains associated with individual channel signals while said collimator is installed, said apparatus comprising: a processor for defining a strip area associated with an obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; said processor for recording a set of total energy signals of said photomultiplier array for a sample of gamma events detected within said strip area of said obscured photomultiplier; said processor for determining a representative total energy signal of said set of total energy signals; and said processor for automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a stored reference total energy signal for gamma events occurring within said strip area and (2) said representative total energy signal.
Claim 13
Dependent Claim
42 words
A gain calibration apparatus as described in claim 10 wherein said installed collimator comprises a first region obscuring gamma ray passage and a second region allowing passage of collimated gamma rays and wherein said obscured photomultiplier is aligned with said first region.
Claim 14
Dependent Claim
22 words
A gain calibration apparatus as described in claim 11 wherein said strip region is aligned with said second region of said collimator.
Claim 15
Dependent Claim
29 words
A gain calibration apparatus as described in claim 12 wherein said strip area is an arc shaped narrow two dimensional area centered about the center of said obscured photomultiplier.
Claim 16
Dependent Claim
47 words
A gain calibration apparatus as described in claim 11 further comprising controlled gain circuitry coupled to a channel signal generated by said obscured photomultiplier, said controlled gain circuitry for applying said preamplification gain to said channel signal, wherein said controlled gain circuitry is responsive to said processor.
Claim 17
Dependent Claim
185 words
A gamma camera system comprising: (a) a scintillation detector comprising: a photomultiplier array wherein each photomultiplier generates a channel signal; and an installed collimator having a first region obscuring gamma ray passage and a second region allowing passage of collimated gamma rays; and (b) gain correction circuitry coupled to receive channel signals from said scintillation detector, said gain correction circuitry for automatically calibrating gains associated with individual channel signals while said collimator is installed, said gain correction circuitry comprising: a processor for defining a strip area associated with an obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; said processor for recording a set of responses of said obscured photomultiplier for a sample of gamma events detected within said strip area; said processor for determining a representative response of said set of responses; and said processor for automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a predetermined and stored reference response of said obscured photomultiplier to gamma events detected within said strip area and (2) said representative response of said obscured photomultiplier.
Claim 18
Dependent Claim
185 words
A gamma camera system comprising: (a) a scintillation detector comprising: a photomultiplier array wherein each photomultiplier generates a channel signal; and an installed collimator having a first region obscuring gamma ray passage and a second region allowing passage of collimated gamma rays; and (b) gain correction circuitry coupled to receive channel signals from said scintillation detector, said gain correction circuitry for automatically calibrating gains associated with individual channel signals while said collimator is installed, said gain correction circuitry comprising: a processor for defining a strip area associated with an obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; said processor for recording a set of responses of said obscured photomultiplier for a sample of gamma events detected within said strip area; said processor for determining a representative response of said set of responses; and said processor for automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a predetermined and stored reference response of said obscured photomultiplier to gamma events detected within said strip area and (2) said representative response of said obscured photomultiplier.
Claim 19
Dependent Claim
22 words
A gamma camera system as described in claim 15 wherein said obscured photomultiplier is aligned with said first region of said collimator.
Claim 20
Dependent Claim
22 words
A gamma camera system as described in claim 16 wherein said strip region is aligned with said second region of said collimator.
Claim 21
Dependent Claim
27 words
A gamma camera system as described in claim 17 wherein said strip area is an are shaped narrow area centered about the center of said obscured photomultiplier.
Claim 22
Dependent Claim
46 words
A gamma camera system as described in claim 16 further comprising controlled gain circuitry coupled to a channel signal generated by said obscured photomultiplier, said controlled gain circuitry for applying said preamplification gain to said channel signal, wherein said gain circuitry is responsive to said processor.
Claim 23
Dependent Claim
50 words
A gamma camera system as described in claim 16 wherein said processor determines a first response of said obscured photomultiplier at initial calibration of said scintillation detector based on gamma events occurring within said strip area when said collimator is removed, wherein said first response is said stored reference response.
Claim 24
Dependent Claim
113 words
A gamma camera system as described in claim 20 wherein said processor defines a central area associated with a central photomultiplier of said photomultiplier array wherein said central area is located above the surface of said central photomultiplier; said processor for recording a set of responses of said central photomultiplier for a sample of gamma events detected within said central area; said processor for determining a representative response of said set of responses of said central photomultiplier; and said processor for automatically adjusting a preamplification gain associated with said central photomultiplier based on (1) a predetermined and stored reference response of said central photomultiplier and (2) said representative response of said central photomultiplier.
Claim 25
Dependent Claim
22 words
A gamma camera system as described in claim 21 wherein said central photomultiplier is aligned with said second region of said collimator.
Claim 26
Dependent Claim
132 words
In a gamma camera system having a scintillation detector with a photomultiplier array, wherein each photomultiplier generates a channel signal, a method of automatically calibrating gains associated with individual channel signals, said method comprising the steps of: installing a collimator onto said scintillation detector wherein said collimator is aligned to cover a section of an obscured photomultiplier; defining a strip area associated with said obscured photomultiplier of said photomultiplier array; recording a set of responses of said obscured photomultiplier for a sample of gamma events detected within said strip area; determining a representative response of said set of responses; and automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a predetermined and stored reference response of said obscured photomultiplier and (2) said representative response of said obscured photomultiplier.
Claim 27
Dependent Claim
132 words
In a gamma camera system having a scintillation detector with a photomultiplier array, wherein each photomultiplier generates a channel signal, a method of automatically calibrating gains associated with individual channel signals, said method comprising the steps of: installing a collimator onto said scintillation detector wherein said collimator is aligned to cover a section of an obscured photomultiplier; defining a strip area associated with said obscured photomultiplier of said photomultiplier array; recording a set of responses of said obscured photomultiplier for a sample of gamma events detected within said strip area; determining a representative response of said set of responses; and automatically adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a predetermined and stored reference response of said obscured photomultiplier and (2) said representative response of said obscured photomultiplier.
Claim 28
Dependent Claim
54 words
An automatic gain calibration method as described in claim 23 wherein said collimator comprises a first region obscuring gamma ray passage and a second region allowing passage of collimated gamma rays and wherein said step of installing said collimator comprises the step of aligning said obscured photomultiplier with said first region of said collimator.
Claim 29
Dependent Claim
31 words
An automatic gain calibration method as described in claim 23 further comprising the step of aligning said strip region associated with said obscured photomultiplier with said second region of said collimator.
Claim 30
Dependent Claim
28 words
An automatic gain calibration method as described in claim 25 wherein said strip area is an arc shaped narrow area centered about the center of said obscured photomultiplier.
Claim 31
Dependent Claim
32 words
An automatic gain calibration method as described in claim 25 further comprising the step of applying said preamplification gain to said channel signal generated by said obscured photomultiplier with said preamplification gain.
Claim 32
Dependent Claim
59 words
An automatic gain calibration method as described in claim 25 further comprising the step of determining, when said gamma camera system is initially calibrated, a first reference response by recording responses of said obscured photomultiplier to gamma events detected within said strip area when said collimator is not installed, wherein said first reference response is said stored reference response.
Claim 33
Dependent Claim
107 words
An automatic gain calibration method as described in claim 28 further comprising the steps of: defining a central area associated with a central photomultiplier of said photomultiplier array wherein said central area is located above the surface of said central photomultiplier; recording a set of responses of said central photomultiplier for a sample of gamma events detected within said central area; determining a representative response of said set of responses of said central photomultiplier; and automatically adjusting a preamplification gain associated with said central photomultiplier based on (1) a predetermined and stored reference response of said central photomultiplier and (2) said representative response of said central photomultiplier.
Claim 34
Dependent Claim
26 words
An automatic gain calibration method as described in claim 29 further comprising the step of aligning said central photomultiplier with said second region of said collimator.
Claim 35
Dependent Claim
64 words
An automatic gain calibration method as described in claim 30 wherein step of automatically adjusting a preamplification gain associated with said obscured photomultiplier comprises the steps of: increasing said preamplification gain of said obscured photomultiplier if said representative response is lower than stored reference response; and decreasing said preamplification gain of said obscured photomultiplier if said representative response is higher than stored reference response.
Claim 36
Dependent Claim
154 words
In a gamma camera system having a scintillation detector with a photomultiplier array, wherein each photomultiplier generates a channel signal, a method of automatically calibrating gains associated with individual channel signals, said method comprising the steps of: installing a collimator onto said scintillation detector wherein said collimator is aligned to cover a section of an obscured photomultiplier; defining a strip area associated with said obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; recording a set of total energy signals of said photomultiplier array for a sample of gamma events detected within said strip area of said obscured photomultiplier; determining a representative total energy signal of said set of total energy signals; and adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a stored reference total energy signal for gamma events occurring within said strip area and (2) said representative total energy signal.
Claim 37
Dependent Claim
154 words
In a gamma camera system having a scintillation detector with a photomultiplier array, wherein each photomultiplier generates a channel signal, a method of automatically calibrating gains associated with individual channel signals, said method comprising the steps of: installing a collimator onto said scintillation detector wherein said collimator is aligned to cover a section of an obscured photomultiplier; defining a strip area associated with said obscured photomultiplier of said photomultiplier array wherein said installed collimator covers a section of said obscured photomultiplier; recording a set of total energy signals of said photomultiplier array for a sample of gamma events detected within said strip area of said obscured photomultiplier; determining a representative total energy signal of said set of total energy signals; and adjusting a preamplification gain associated with said obscured photomultiplier based on (1) a stored reference total energy signal for gamma events occurring within said strip area and (2) said representative total energy signal.
Claim 38
Dependent Claim
75 words
An automatic gain method as described in claim 32 wherein said collimator comprises a first region obscuring gamma ray passage and a second region allowing passage of collimated gamma rays and wherein said step of installing said collimator comprises the step of aligning said obscured photomultiplier with said first region of said collimator and further comprising the step of aligning said strip region associated with said obscured photomultiplier with said second region of said collimator.
Claim 39
Dependent Claim
28 words
An automatic gain method as described in claim 33 further comprising the step of determining said stored reference total energy signal at initial calibration of said scintillation detector.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-09-11 | 1999-03-13 | 1999-09-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-09-11 | 2003-03-13 | 2003-09-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-09-11 | 2007-03-13 | 2007-09-12 | $7700.00 | Window Closed / Lapsed |