Patent ID: 6297506
Filing Date: 2001-10-02
Classification: A61B,G01T

Abstract:
A method for reducing pile-up errors in connection with the use of detectors having a plurality of scintillating crystals, the detectors receiving gamma rays, and each of the plurality of scintillating crystals having a different decay constant, said method comprising the steps of:determining an appropriate integration time for each of said plurality of scintillating crystals, including an integration time for a first of said plurality of scintillating crystals having a first decay constant, and an integration time for each other of said plurality of scintillating crystals, determination of said appropriate integration time being based upon a light decay time of each of said plurality of scintillating crystals and a percentage of the total crystal light output required, and wherein said decay constant for each of said other of said plurality of scintillating crystals is slower than said first decay constant;converting light generated by one of said plurality of scintillating crystals upon interaction with a gamma ray, into a pulse of electrical energy using a photon converter;beginning integration of said pulse of electrical energy;taking first and second samples of said pulse of electrical energy to determine a rate of light decay within one of said plurality of scintillating crystals, said first and second samples taken during the integration time selected for said first of said plurality of scintillating crystals having said first decay constant;calculating the ratio of said first sampled pulse of electrical energy to said second sampled pulse of electrical energy to determine whether said gamma ray event occurred in said first of said plurality of scintillating crystals or in one of said other of said plurality of scintillating crystals having a slower decay constant, said ratio being larger for said first scintillating crystal than for any of said other scintillating crystals;identifying in which of said plurality of scintillating crystals said gamma ray event occurred;stopping said integration at said selected integration time for said first scintillating crystal having the faster decay constant if said gamma ray event is determined to have occurred in said first of said plurality of scintillating crystals; andcontinuing said integration for said selected integration time for said identified other of said scintillating crystals if said gamma ray event is determined not to have occurred in said first of said plurality of scintillating crystals, thereby acquiring a higher percentage of light.