Patent ID: 8476600

Claim:
An apparatus for measuring a Depth-Of-Interaction (DOI) using a light dispersion, the apparatus comprising: a crystal layer of a mono layer in which a plurality of crystals for absorbing gamma rays are adjacent and consecutively arranged; scintillation light detectors disposed at one end of the crystals and configured to detect scintillation light emitted from the crystal layer by the gamma rays; a change material included in the crystals and configured to linearly change transmittance in a length direction of the crystals; and a control unit configured to calculate the DOI in the crystal layer on a basis of a first output signal and a second output signal; the scintillation light detectors outputting the first output signal in one direction and the second output signal in a direction perpendicular to the one direction; said control unit configured to calculate the DOI of the crystal layer by at least calculating an amount of a variance value of photon distribution in each of the directions on the basis of the first output signal and the second output signal, inducing an angle of the DOI on the basis of the variance value of the number of photons, and calculating the DOI on the basis of the angle of the DOI.