| 摘要 |
The specification describes an instrument and a method for determining information about an object (J), only one side of which is available for examination. The method involves exposing the object to gamma-rays and measuring the position and/or time of arrival of gamma-rays at a detector (D). The instrument includes a source of gamma-rays (S) located so that at least some gamma-rays impact upon the object, and a detector surrounded by a shield (C) having an aperture (A) for facing at the object to be studied. The detector is capable of measuring the position and/or time of arrival at the detector of gamma-rays passing through the aperture.
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