A new detector was designed to improve the spatial resolution of positron emission tomography (PET) and
acquire digital coordinates of the detector's scintillation pixels. In order to solve the spatial resolution deterioration
phenomenon due to parallax error occurring outside the field of view (FOV), a method of measuring the
depth of interaction was developed, and this was accomplished with the acquisition of digital coordinates. A
detector using a 4 × 4 × 2 GAGG scintillator was designed using the DETECT2000 simulation tool to acquire
digital coordinates of the scintillation pixels and measure the depth of interaction of the two layers. A gammaray
reaction was generated in all the scintillation pixels, and the signals were obtained from SiPM pixels in a 4
× 4 array. The 16-channels of optical sensor signals were reduced to signals of 4 channels, and these were calculated
as a ratio of each signal. The ratio of the signal was obtained from all the flash pixels, and the position
was obtained as digital coordinates by comparing it with the ratio of the signal by the gamma ray response generated
at the new position. In order to evaluate the accuracy of acquiring the digital coordinates and the accuracy
of the layer where the scintillation pixel in which the scintillator and the gamma ray reacted, a signal was
obtained by generating a gamma ray response for the entire length of each scintillation pixel. Gamma-ray reactions
were generated at intervals of 0.2 mm from 0.1 mm to 19.9 mm. The obtained signals through these reactions
were compared with the signals of each scintillation pixel obtained in advance. Then, the accuracy of
measured positions on the X, Y, and Z axes were evaluated. The accuracy of both the X and Y axis showed perfect
results, and the accuracy of the Z axis was 91.46 %.