Patent ID: 8519341

Claim:
Radiation tomography apparatus comprising: a detector ring formed by arranging two or more ring units as to share central axes of the two or more ring units, the two or more ring units each being formed by arranging unit detector rings having radiation detecting elements for detecting radiation arranged annularly as to share central axes of the unit detector rings, a direct coincidence device for counting a number of coincidence events as a number of times that two different radiation detecting elements belonging to one of the two or more ring units detect radiation coincidently; a cross coincidence device that is connected to both a first ring unit and a second ring unit adjacent to each other, and counts a number of coincidence events as a number of times that two different radiation detecting elements belonging to each of the first ring unit and the second ring unit detect radiation coincidently only when a distance between two radiation detecting elements in a direction of the central axes is equal to or less than a given length; a given length storage device for storing the given length; and an input device for inputting the given length, the given length being variable in accordance with input by the input device.