Patent US2723380A successfully refreshed from Google Patents.
US5530248A
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US
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Method of and apparatus for improving gamma camera image
Assignee: GE Medical Systems Israel Ltd
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Filing: 1995-05-30
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Granted: 1996-06-25
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Expires: 2015-05-30
Abstract
Abstract A system for recording fewer of the events that are caused by unwanted photons with greater stability. The system locally determines the energy spectrum and fits for each pixel of the image the determined energy spectrum with a modified trial function composed of: a photopeak component of known energy shape, Compton scatter components having theoretically derived energy shapes and, when applicable, also measured or calculated energy spectra of other unwanted photons. The modified trial function also takes into consideration unknown local deviations in the outputs of electronic components. The amplitude of the photopeak distribution resulting from the fit is used to obtain the local content of wanted interactions in the image. This enables removal of Compton contamination and also the contamination caused by interaction of the gamma photons with lead components.
Inventors
- 👤 Alex Natanzon
- 👤 Gideon Berlad
- 👤 Dov Maor
- 👤 Yigal Shrem
- 👤 Adrian Soil
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 00:23
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/161; G01T1/164; G01T1/1641; G01T1/1647; G01T1/1642; G01T1/1648
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
124 words
A method for improving an image of a gamma camera system by reducing the contribution of unwanted photons detected by the detector of the camera, said method comprising: a) determining an energy spectrum at each X,Y location of the detector for wanted and unwanted photons; b) determining a system dependent energy distribution of unwanted photons; c) determining an energy spread function for wanted photons; d) constructing a trial function that is dependent on the energy spread function and the system-dependent energy distribution; e) modifying the trial function with the first derivative of the energy spread function to form a modified trial function; and f) fitting the modified trail function the determined energy spectrum to obtain the count of wanted photons at each X,Y location.
Claim 2
Independent Claim
124 words
A method for improving an image of a gamma camera system by reducing the contribution of unwanted photons detected by the detector of the camera, said method comprising: a) determining an energy spectrum at each X,Y location of the detector for wanted and unwanted photons; b) determining a system dependent energy distribution of unwanted photons; c) determining an energy spread function for wanted photons; d) constructing a trial function that is dependent on the energy spread function and the system-dependent energy distribution; e) modifying the trial function with the first derivative of the energy spread function to form a modified trial function; and f) fitting the modified trail function the determined energy spectrum to obtain the count of wanted photons at each X,Y location.
Claim 3
Dependent Claim
135 words
Apparatus for improving an image of a gamma camera system by reducing the contribution of unwanted photons detected by the detector of the camera, said method comprising: a) means for determining an energy spectrum at each X,Y location of the detector for wanted and unwanted photons; b) means for determining a system dependent energy distribution of unwanted photons; c) means for determining an energy spread function for wanted photons; d) means for constructing a trial function that is dependent on the energy spread function and the system-dependent energy distribution; e) means for modifying the trial function with the first derivative of the energy spread function to form a modified trial function; and f) means for fitting the modified trial function to said energy spectrum to obtain the count of wanted photons at each X,Y location.
Claim 4
Dependent Claim
135 words
Apparatus for improving an image of a gamma camera system by reducing the contribution of unwanted photons detected by the detector of the camera, said method comprising: a) means for determining an energy spectrum at each X,Y location of the detector for wanted and unwanted photons; b) means for determining a system dependent energy distribution of unwanted photons; c) means for determining an energy spread function for wanted photons; d) means for constructing a trial function that is dependent on the energy spread function and the system-dependent energy distribution; e) means for modifying the trial function with the first derivative of the energy spread function to form a modified trial function; and f) means for fitting the modified trial function to said energy spectrum to obtain the count of wanted photons at each X,Y location.
Claim 5
Independent Claim
237 words
A method for improving images produced by an Anger-type gamma camera utilizing isotopes having k photopeaks, where k>=1, by reducing the contribution of unwanted photons in an image of a subject produced by the gamma camera as a result of photons impinging a detector of the camera, said method including the steps of: a) detecting photons that impinge on said detector by determining the energy of a photon, and computing its X,Y coordinates if the determined energy is within certain limits; b) determining an energy spectrum of detected photons at each of the X,Y coordinates; c) determining a system-dependent energy distribution of different components of unwanted photons; d) determining the energy spread function of the gamma camera for the known energies of wanted photons; e) constructing a trial function in terms of said system-dependent energy distribution of unwanted photons and said energy spread function of the gamma camera for the known energies of wanted photons; f) processing said trial function to account for local unknown systematic energy deviations between actual and measured energy of the detected photons while preserving the whole logic of the processing to form a modified trial function representing the energy distribution that includes wanted and unwanted detected photons; g) fitting the modified trial function to the determined energy spectrum to obtain the count of wanted photons; and f) using the count of wanted photons to produce an image practically free of unwanted photons.
Claim 6
Independent Claim
237 words
A method for improving images produced by an Anger-type gamma camera utilizing isotopes having k photopeaks, where k>=1, by reducing the contribution of unwanted photons in an image of a subject produced by the gamma camera as a result of photons impinging a detector of the camera, said method including the steps of: a) detecting photons that impinge on said detector by determining the energy of a photon, and computing its X,Y coordinates if the determined energy is within certain limits; b) determining an energy spectrum of detected photons at each of the X,Y coordinates; c) determining a system-dependent energy distribution of different components of unwanted photons; d) determining the energy spread function of the gamma camera for the known energies of wanted photons; e) constructing a trial function in terms of said system-dependent energy distribution of unwanted photons and said energy spread function of the gamma camera for the known energies of wanted photons; f) processing said trial function to account for local unknown systematic energy deviations between actual and measured energy of the detected photons while preserving the whole logic of the processing to form a modified trial function representing the energy distribution that includes wanted and unwanted detected photons; g) fitting the modified trial function to the determined energy spectrum to obtain the count of wanted photons; and f) using the count of wanted photons to produce an image practically free of unwanted photons.
Claim 7
Dependent Claim
77 words
The method according to claim 3 wherein said trial function is constructed by multiplying the energy spread function of wanted photons by a first unknown coefficient of wanted photons, and adding thereto, the system dependent energy distribution of unwanted photons multiplied by their unknown coefficients, and wherein said trial function is modified by including in the trial function the first n derivatives of the energy spread function of each of the k photopeaks multiplied by unknown coefficients.
Claim 8
Dependent Claim
99 words
The method of claim 4 wherein the step of determining the system dependent energy distributions of the different components of unwanted photons comprises the steps of: a) determining at least part of the system independent energy distributions of the components of the unwanted photons, b) determining the energy spread function of the gamma camera system for the determined energies of the components of the unwanted photons; and c) using the determined energy distribution of unwanted photons and the energy spread function of the system to obtain a system dependent energy distribution of the unwanted photons per X,Y coordinate location.
References Cited (Backward Citations)
US4780823A
Cited
US4839808A
Cited
US5315506A
Cited
US5227968A
Cited
US5293195A
Cited
US5434414A
Cited
US5438202A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-06-25 | 1999-12-25 | 2000-06-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-06-25 | 2003-12-25 | 2004-06-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-06-25 | 2007-12-25 | 2008-06-25 | $7700.00 | Window Closed / Lapsed |