POSITRON CT APPARATUS AND A TIMING CORRECTION METHOD

摘要

A PET apparatus and a timing correction method of this invention select two target gamma-ray detectors which count coincidences, select a reference detector which is one detector out of the two selected gamma-ray detectors, select a gamma-ray detector different from the other, opposite detector, and when repeating the selection, make a time lag histogram concerning two gamma-ray detectors selected in the past a reference, and correct a time lag histogram concerning gamma-ray detectors selected this time based on the reference. By repeating an operation to make the corrected time lag histogram concerning the two gamma-ray detectors a new reference, an optimal time lag histogram can be obtained without repeating many measurements and computations.

主权项

1. A positron CT apparatus having a plurality of detectors for detecting radiation released from a positron-emitting radioactive drug given to a patient, comprising:
a computing device, in connection with a time lag histogram showing a count value distribution of time lag variations for each pair of detectors which count coincidences of the radiation, for selecting two target detectors which count coincidences, selecting one detector out of the two selected detectors, selecting a detector different from the other detector, and when repeating the selection, making a time lag histogram concerning two detectors selected in the past a reference, correcting a time lag histogram concerning detectors selected this time based on the reference, and repeating an operation to make the corrected time lag histogram concerning the two detectors a new reference; and a coincidence counting circuit for counting coincidences of the radiation based on the time lag histogram for each pair of detectors repeatedly corrected by the computing device wherein: the detector includes: a plurality of scintillator elements which produce fluorescence upon incidence of the radiation; and a photoelectric conversion device which detects the radiation by carrying out photoelectric conversion of light from each scintillator element and in connection with the time lag histogram for each pair of scintillator element units each consisting of one scintillator element of each of the detectors which count coincidences of the radiation, the computing device selects two scintillator element units of target detectors which count coincidences, selects one scintillator element unit of the detector out of the two selected scintillator element units, selects a scintillator element unit different from the other scintillator element unit of the detector, and when repeating the selection, makes a time lag histogram concerning two scintillator element units of detectors selected in the past a reference, corrects a time lag histogram concerning scintillator element units of detectors selected this time based on the reference, and repeats an operation to make the corrected time lag histogram concerning the two scintillator element units of the detectors a new reference; and the coincidence counting circuit counts the coincidences of the radiation based on the time lag histogram for each pair of scintillator element units of detectors repeatedly corrected by the computing device.