Depth of Interaction in PET Detector Design: Performance Optimization With Light-Sharing Window

The spatial resolution and image quality of positron emission tomography (PET) scanners are significantly affected by the uncertainties in the depth-of-interaction (DOI) measurement in PET detectors. The existing methods for implementing the DOI measurements mainly include dual-layer and dual-end crystal detectors. However, dual-layer crystal detectors have poor DOI resolution and limited performance improvement, whereas dual-end crystal detectors have a complex structure and high cost. To address these shortcomings, this article proposes a cost-effective detector with a light-sharing window comprising a simple structure and good DOI resolution. The proposed detector leverages the ratio of photons passing through the internal light-sharing window at different interaction depths to determine the DOI. The proposed design is validated using a Lu<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2(1-x)}$ </tex-math></inline-formula>Y2xSiO5 (LYSO) scintillation crystal detector, with a single crystal of size <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2\times 20$ </tex-math></inline-formula> mm, and a feedforward neural network. The results show that the DOI resolution achieves a full-width at half-maximum of 3.0 mm and a mean absolute error (MAE) of 2.1 mm, which significantly improves the PET image quality. Moreover, the results also indicate a direct correlation between the energy and time resolution of the detector and the DOI. Furthermore, the results show that the proposed detector calibrates energy and time measurements through DOI, thus improving its performance and providing better PET image quality. The methods and results presented in this study can help in further improving the performance of PET detectors and PET scanners.