| 摘要 |
PURPOSE:To simply, accurately measure scattering simultaneous count by placing a gamma-ray absorber between each pair of detectors of many pairs of detector rings disposed at symmetrical positions and rotating it along a concentric circle with the rings. CONSTITUTION:A rodlike gamma-ray absorber 26 is placed inside gamma-rays detector rings arranged in a ring state, and rotated on a concentric circumference with the rings. When the absorber 26 is moved to opposed lines of a pair of gamma-ray detectors 12-N1 and 12-N2, positrons at a point 29 of an object 30 to be exposed collide with electrons of the object 30. Even if 7-rays are emitted toward the detectors N1, N2, the gamma-rays directed toward the detector N1 are absorbed the absorber 26, and only the t-rays directed toward the detector N2 are detected. Accordingly, scattering simultaneous counted value indicated at the other positrons 31 is measured by the detector N1, N2. If there is no absorber 26, an ordinary simultaneous counting is measured. A true simultaneous counting is obtained by removing scattering simultaneous counting from the measured simultaneous counting, and a positron image having high quantitativity is reformed.
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