标题： 用于正电子发射断层扫描中测量伽马射线偏振的探测器模块优化 显示英文标题

标题： Optimization of detector modules for measuring gamma-ray polarization in Positron Emission Tomography

摘要： 在正电子发射断层扫描（PET）中，检测$\gamma$射线偏振目前仍是一个未被开发的特性，可以作为额外的手段来提高这种成像模式的信噪比。 $\gamma$偏振与康普顿散射过程中的方位角有关，因此湮灭量子的初始偏振相关性转化为在两个湮灭光子都发生康普顿散射的事件中方位角的相关性。 这导致真实事件的方位角差呈现调制分布，而背景事件则没有这种调制。 我们对基于闪烁体矩阵和硅光电倍增管的五种探测器配置进行了全面的实验研究，这些配置适用于测量方位角调制。 模块由GaGG:Ce或LYSO:Ce像素组成，尺寸从1.9x1.9x20$\mathrm{mm^3}$到3x3x20$\mathrm{mm^3}$不等。 这些模块的独特之处在于它们可以通过检测反冲电子和散射伽马射线在单个探测器层中重建康普顿散射，这简化了扩展到更大系统的进程。 方位角差的幅度调制在所有配置中都清晰可见，从$0.26\pm0.01$到$0.34\pm 0.02$不等，具体取决于事件选择标准。 结果表明，更精细的探测器分割在实现更高的调制因子中起着主导作用。 显示英文摘要

摘要： Detection of $\gamma$-ray polarization in Positron Emission Tomography (PET) is as yet an unexploited feature that could be used as an additional handle to improve signal-to-background ratio in this imaging modality. The $\gamma$ polarization is related to the azimuthal angle in the Compton scattering process, so the initial correlation of polarizations of the annihilation quanta translates to the correlation of the azimuthal angles in events where both annihilation photons undergo Compton scattering. This results in a modulated distribution of the azimuthal angle difference for true events, while this modulation is lacking for the background events. We present a comprehensive experimental study of five detector configurations based on scintillator matrices and silicon photomultipliers, suitable for measuring the azimuthal modulation. The modules consist of either GaGG:Ce or LYSO:Ce pixels with sizes varying from 1.9x1.9x20 $\mathrm{mm^3}$ to 3x3x20 $\mathrm{mm^3}$. The distinctive feature of the modules is that they can reconstruct the Compton scattering by detecting the recoil electron and the scattered gamma in a single detector layer, which simplifies extension to larger systems. The amplitude modulation of the azimuthal angles' difference is clearly observable in all configurations ranging from $0.26\pm0.01$ to $0.34\pm 0.02$ depending on the event selection criteria. The results suggest that finer detector segmentation plays a leading role in achieving higher modulation factors.