Background reduction in PET by double Compton scattering of quantum entangled annihilation photons

Abstract

Abstract The reduction of background events, such as random and scatter events, can improve positron emission tomography (PET) images quantitatively. The quantum entanglement property of annihilation photons has been theoretically studied and experimentally validated. Recently, simulation studies on PET image reconstruction using the quantum entanglement property of annihilation photons and studies on the measurement of entanglement and polarization properties with scintillation crystal arrays demonstrated that PET images with less background can be achieved. This study utilized the quantum entanglement property of annihilation photons in a typical PET system with block detectors. A data acquisition method for quantum entanglement PET (QEPET) and system response modelling for QEPET image reconstruction were proposed and implemented. An experimental study was conducted using a small animal PET system composed of Ce:GAGG scintillation crystals whose dimensions are 2.5 × 2.5 × 4mm3. The diameter of the system was 79.3 mm. Signals from all individual crystals were processed parallelly and independently; thus, Compton scatter and absorption crystals within a module were obtained directly. The 28 MBq experiment result revealed the random background ratio of QEPET was approximately 20% lower than that of PET and the count rate of QEPET was approximately 0.1% that of PET. Evaluation on reconstructed images from the 28 MBq experiment revealed that the signal-to-background ratio of QEPET was approximately two times better than that of PET while the signal-to-noise ratio of QEPET was about 77% of that of PET. The method proposed in this study is expected to improve PET images with high background, such as those with a high activity and high background gamma rays and improve range verification in proton therapy.