DOI Detector Design with Multiple Layers of Scintillation Pixel Arrays of Different Sizes

We designed a detector that distinguishes between four layers at different interaction depths, using scintillation pixels of different sizes for each layer, and applying arrays of different sizes. The lowest layer has the largest array, and the size of the array is designed to decrease by one scintillation pixel when proceeding from the layer below to the layer above, such that the location of the scintillation pixels in each layer is misaligned. To evaluate the depth of interaction layer discrimination of the designed detector, a flood image was obtained by generating gamma-ray events at all scintillation pixels. In addition, a light guide was used to prevent the images of the scintillation pixels from overlapping at the corner, which may occur due to the use of small scintillation pixels. After obtaining the flood image by applying various light guide thicknesses, the degree of separation of the scintillation pixel image formed at the corner was evaluated. The application of a light guide with a thickness of 1 mm was evaluated to provide the highest degree of separation, which means that the thickness of the light guide capable of obtaining the best image was 1 mm. The flood image confirmed that the scintillation pixels of all layers appeared separated at the light guide thickness of 1 mm, and as a result thereof, it was confirmed that it could be used as a four-layer scintillation detector for measuring the depth of interaction in the detector. The application of this detector to positron emission tomography for small animals is considered capable of solving the deterioration in spatial resolution that may occur outside the field of view.