Development of a depth-of-interaction detector using alignment difference of scintillation pixels between layers

To resolve the deterioration in spatial resolution in the peripheral field of view of small-animal positron emission tomography (PET) systems, a detector for measuring the depth of interaction was developed. A scintillation pixel array composed of two layers was configured to be staggered by varying the size of the scintillation pixels in each layer, and the size of the arrangement was different. The top layer consists of 3 mm × 3 mm × 10 mm GAGG scintillators in a 4 × 4 array, and the bottom layer consists of 2 mm × 2 mm × 10 mm GAGG scintillators in a 6 × 6 array. The configured scintillator was combined with an optical sensor to form the entire detector. To evaluate whether the detector measures the interaction depth, a flood image was acquired using a Na-22 radiation source that emitted 511 keV γ-rays. The acquired flood image, confirmed that the top-layer and bottom-layer scintillation pixels were imaged at different positions. Thus, it is possible to separate the layer, in which the scintillation pixels and γ-rays interact, from the flood image to resolve the deterioration obtain excellent-quality images.