Image Reconstruction Analysis for Positron Emission Tomography with Heterostructured Scintillators

The concept of structure engineering has been proposed for the exploration of the next generation of radiation detectors with improved performance. A Time Of Flight Positron Emission Tomography (TOF-PET) scanner with heterostructured scintillators with a pixel size of 3.0×3.1×15 mm³ was simulated. The heterostructures consisted of alternating layers of BGO as a dense material with high stopping power and plastic as a fast light emitter. Using the GATE simulation toolkit, a detector time resolution was calculated as a function of the deposited and shared energy in both materials on an event-by-event basis. We saw that while sensitivity was reduced to 32% for 100 µm thick plastic layers and 52% for 50 µm, the CTR distribution improved to 204±49 ps and 220±41 ps respectively, compared to 276±9 ps for bulk BGO. We divided the events into three groups based on their CTR and modeled them with different Gaussian TOF kernels. On a NEMA IQ phantom, the heterostructures had better contrast recovery in early iterations, while on the other hand, BGO achieved a better Contrast-to-Noise Ratio (CNR) after the 10th - 15th iteration due to the higher sensitivity. The developed simulation and reconstruction methods constitute new tools for evaluating different detector designs with complex time responses.