Method To Determine The Depth-Of-Interaction Function For PET Detectors
First Claim
1. A method of determining a depth-of-interaction (DOI) function of a detector having a scintillation crystal and first and second photosensitive detectors arranged one at each opposite end face of the crystal for detecting scintillation interactions within the crystal, the method comprising the steps of:
- irradiating the crystal to provide a predetermined distribution of scintillation interactions along a depth axis of the crystal extending between the opposite end faces of the crystal;
collecting a plurality of output signal pairs each including a first output signal associated with the first photosensitive detector and a second output signal associated with the second photosensitive detector, each collected output signal pair corresponding to a respective scintillation interaction at a specific DOI position z;
calculating a signal ratio R for each of the plurality of output signal pairs, the signal ratio R representing a strength of the first output signal relative to the sum of the first and second output signals; and
applying probability theory to the calculated signal ratios R to determine a cumulated distribution function CDF(R), the cumulated distribution function CDF(R) indicating DOI position z as a function of signal ratio R.
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Abstract
A three-dimensional PET detector of a type having a scintillation crystal and first and second photosensitive detectors arranged one at each opposite end face of the crystal for detecting scintillation interactions within the crystal is calibrated to determine a depth-of-interaction (DOI) function thereof by irradiating the crystal to cause a predetermined distribution of interactions along a depth axis of the crystal, and applying probability theory to signal data collected by the two photosensitive detectors. The method provides a DOI function that indicates DOI position as a function of a signal ratio R obtained from the signal data.
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Citations
11 Claims
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1. A method of determining a depth-of-interaction (DOI) function of a detector having a scintillation crystal and first and second photosensitive detectors arranged one at each opposite end face of the crystal for detecting scintillation interactions within the crystal, the method comprising the steps of:
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irradiating the crystal to provide a predetermined distribution of scintillation interactions along a depth axis of the crystal extending between the opposite end faces of the crystal;
collecting a plurality of output signal pairs each including a first output signal associated with the first photosensitive detector and a second output signal associated with the second photosensitive detector, each collected output signal pair corresponding to a respective scintillation interaction at a specific DOI position z;
calculating a signal ratio R for each of the plurality of output signal pairs, the signal ratio R representing a strength of the first output signal relative to the sum of the first and second output signals; and
applying probability theory to the calculated signal ratios R to determine a cumulated distribution function CDF(R), the cumulated distribution function CDF(R) indicating DOI position z as a function of signal ratio R. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a method of determining a depth-of-interaction (DOI) function of a detector having a scintillation crystal and first and second photosensitive detectors arranged one at each opposite end face of the crystal for detecting scintillation interactions within the crystal, the improvement comprising the step of:
irradiating the crystal with radiation from a stationary source providing a predetermined distribution of scintillation interactions along a depth axis of the crystal extending between the opposite end faces of the crystal. - View Dependent Claims (8)
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9. In a method of determining a depth-of-interaction (DOI) function of a detector having a scintillation crystal and first and second photosensitive detectors arranged one at each opposite end face of the crystal for detecting scintillation interactions within the crystal, the improvement comprising the step of:
applying probability theory to determine a cumulated distribution function CDF(R), the cumulated distribution function CDF(R) indicating DOI position z as a function of a signal ratio R calculated from a first output signal and a second output signal generated by the first and second photosensitive detectors, respectively. - View Dependent Claims (10)
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11. A method of determining a drifted depth-of-interaction (DOI) function of a detector having a scintillation crystal and first and second photosensitive detectors arranged one at each opposite end face of the crystal for detecting scintillation interactions within the crystal, an initial DOI function of the detector being known, the method comprising the steps of:
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a) irradiating the crystal to provide a distribution of scintillation interactions along a depth axis of the crystal extending between the opposite end faces of the crystal;
b) collecting a plurality of output signal pairs each including a first output signal associated with the first photosensitive detector and a second output signal associated with the second photosensitive detector, each collected output signal pair corresponding to a respective scintillation interaction at a specific DOI position z;
c) calculating a signal ratio R for each of the plurality of output signal pairs, the signal ratio R representing a strength of the first output signal relative to the sum of the first and second output signals; and
d) applying probability theory to the calculated signal ratios R to determine a first cumulated distribution function CDF0(R);
e) repeating steps (a) through (d) after drift has occurred, including providing the same distribution of scintillation interactions along a depth axis of the crystal, to determine a second cumulated distribution function CDF1(R);
f) calculating a drift scale factor M(R)=CDF1(R)/CDF0(R); and
g) multiplying the initial DOI function by the drift scale factor M(R) to obtain the drifted DOI function.
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Specification