Patent Number: 
Section: claims

1. A method, comprising:determining whether a specimen to be tested includes at least one positron emitter therein that will be activated in response to photon bombardment;selecting a positron emitter to be activated;determining a threshold photon energy required to activate the selected positron emitter;determining a half-life of the selected positron emitter; andwhen the half-life of the selected positron emitter is less than a selected half-life, then performing a rapid activation/analysis process, said rapid activation/analysis process comprising:activating for an activation time the selected positron emitter by bombarding the specimen with photons having energies at least as great as the threshold photon energy;detecting for a detection time gamma rays produced by annihilation of positrons with electrons in the specimen; andrepeating said steps of activating for an activation time and detecting for a detection time until detecting a sufficient number of gamma rays to determine at least one material characteristic of said specimen;when the half-life of the selected positron emitter is greater than or equal to the selected half-life, then performing a normal activation/analysis process, said normal activation/analysis process comprising:activating the selected positron emitter by bombarding the specimen with photons having energies at least as great as the threshold photon energy; anddetecting gamma rays produced by annihilation of positrons with electrons in the specimen. 2. The method of claim 1, further comprising determining a positron lifetime based on the detected gamma rays. 3. The method of claim 1, further comprising using a Doppler broadening algorithm to determine the at least one material characteristic. 4. The method of claim 1, further comprising using a three dimensional imaging algorithm to determine a position within the specimen of a positron/electron annihilation event. 5. A method, comprising:providing a specimen comprising at least one positron emitter;determining a threshold energy for activating the at least one positron emitter;comparing a half-life of the at least one positron emitter with a selected half-life;when the half-life of the at least one positron emitter is greater than or equal to the selected half-life:activating the at least one positron emitter by bombarding the specimen with photons having energies greater than the threshold energy; anddetecting gamma rays produced by annihilation of positrons with electrons within the specimen; or,when the half-life of the at least one positron emitter is less than the selected half-life:activating for an activation time the at least one positron emitter by bombarding the specimen with photons having energies greater than the threshold energy;detecting for a detection time gamma rays produced by annihilation of positrons with electrons within the specimen; andrepeating said steps of activating for an activation time and detecting for a detection time until detecting a sufficient number of gamma rays to determine at least one material characteristic of said specimen. 6. The method of claim 1, wherein the selected half-life is on the order of tens of seconds. 7. The method of claim 1, wherein selected half-life is about 17 seconds. 8. The method of claim 1, wherein the detection time is about equal to the half-life of the selected positron emitter. 9. The method of claim 1, wherein the rapid activation/analysis process further comprises alternately moving the specimen between an activation position and a detection position, the activation position being adjacent a photon source, the detection position being adjacent a detector. 10. The method of claim 1, wherein the rapid activation/analysis process further comprises alternately moving a photon source adjacent the specimen during the activation time and away from the specimen during the detection time and alternately moving a detector adjacent the specimen during the detection time and away from the specimen during the activation time. 11. The method of claim 1, wherein the rapid activation/analysis process further comprises activating a photon source to bombard the specimen with photons during the activation time and de-activating the photon source during the detection time. 12. The method of claim 5, further comprising determining a positron lifetime based on the detected gamma rays. 13. The method of claim 5, further comprising using a Doppler broadening algorithm to determine the at least one material characteristic. 14. The method of claim 5, further comprising using a three dimensional imaging algorithm to determine a position within the specimen of a positron/electron annihilation event. 15. The method of claim 5, wherein the selected half-life is on the order of tens of seconds. 16. The method of claim 5, wherein selected half-life is about 17 seconds. 17. The method of claim 5, wherein the detection time is about equal to the half-life of the at least one positron emitter. 18. The method of claim 5, further comprising alternately moving the specimen between an activation position and a detection position, the activation position being adjacent a photon source, the detection position being adjacent a detector. 19. The method of claim 5, further comprising alternately moving a photon source adjacent the specimen during the activation time and away from the specimen during the detection time. 20. The method of claim 19, further comprising alternately moving a detector adjacent the specimen during the detection time and away from the specimen during the activation time. 21. The method of claim 5, further comprising activating a photon source to bombard the specimen with photons during the activation time and de-activating the photon source during the detection time. 22. A method, comprising:providing a specimen comprising at least one positron emitter;determining a threshold energy for activating the at least one positron emitter;comparing a half-life of the at least one positron emitter with a selected half-life;when the half-life of the at least one positron emitter is less than the selected half-life:alternately activating the at least one positron emitter and detecting gamma rays produced by annihilation of positrons within the specimen until detecting a sufficient number of gamma rays to determine at least one material characteristic of said specimen. 23. The method of claim 22, wherein said activating the at least one positron emitter comprises activating for an activation time the at least one positron emitter by bombarding the specimen with photons having energies greater than the threshold energy. 24. The method of claim 23, further comprising determining a positron lifetime based on the detected gamma rays. 25. The method of claim 23, further comprising using a Doppler broadening algorithm to determine the at least one material characteristic. 26. The method of claim 23, further comprising using a three dimensional imaging algorithm to determine a position within the specimen of a positron/electron annihilation event. 27. The method of claim 23, wherein the selected half-life is on the order of tens of seconds. 28. The method of claim 23, wherein selected half-life is about 17 seconds. 29. The method of claim 23, wherein detecting gamma rays is performed for a time that is about equal to the half-life of the at least one positron emitter. 30. The method of claim 23, further comprising alternately moving the specimen between an activation position and a detection position, the activation position being adjacent a photon source, the detection position being adjacent a detector. 31. The method of claim 23, further comprising alternately moving a photon source adjacent the specimen during the activation time and away from the specimen during the step of detecting gamma rays. 32. The method of claim 31, further comprising alternately moving a detector adjacent the specimen during the step of detecting gamma rays and away from the specimen during the activation time. 33. The method of claim 23, further comprising activating a photon source to bombard the specimen with photons during the activation time and de-activating the photon source during the step of detecting gamma rays.