Timing properties of phosphor-coated polished LSO crystals
Timing properties of phosphor-coated polished LSO crystals
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DOI：
10.1088/0031-9155/59/15/n139
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发表时间：
2014-08-07
影响因子：
3.5
通讯作者：
Cherry, Simon R.
中科院分区：
文献类型：
--
作者：
Schmall, Jeffrey P.;Roncali, Emilie;Cherry, Simon R.
本研究研究了一种用于正电子发射断层扫描（PET）的飞行时间(TOF)-相互作用深度（DOI）探测器设计，该探测器基于磷涂层氧化硅酸镥（LSO）闪烁体晶体与快速单通道光电倍增管耦合。闪烁光与荧光粉涂层的相互作用以与深度相关的方式改变脉冲形状。对表面抛光的3 × 3 × 10 mm(3) LSO闪烁晶体进行了表征，并对有无磷光体涂层进行了表征，以评估DOI能力和定时性能。研究了两种不同的荧光粉涂层几何形状：晶体顶部表面的涂层，以及晶体顶部加一半侧面的涂层。当仅涂覆顶部表面时，衰减时间的深度依赖性可以忽略不计，然而，当涂覆顶部和一半晶体侧面时，端到端衰减时间有类似的10 ns差异，足以支持使用三个DOI箱（3.3 mm DOI箱宽度）。与未包覆的晶体相比，半包覆的晶体在各深度的上升时间略快，但信号幅度较小。在1 mm深度处，磷光体涂层的能量分辨率为13.7%，在9 mm深度处，半涂层晶体的能量分辨率为15.3%。未包覆的LSO晶体的光峰位置随深度变化不大，能量分辨率为10.4%。两个未涂覆的LSO晶体的正反重合时间分辨率（CTR）为287 ps。采用荧光粉涂层后，顶部涂层晶体的CTR为314 ps，而半涂层晶体的CTR为384 ps。我们证明了时间分辨率和DOI分辨率之间的权衡可以由荧光粉涂层几何形状控制。在这里，我们提出的初步结果表明，良好的DOI分辨率可以实现只有适度的26%的降低CTR。
This study investigates a time-of-flight (TOF)-depth-of-interaction (DOI) detector design for positron emission tomography (PET), based on phosphor-coated lutetium oxyorthosilicate (LSO) scintillator crystals coupled to fast single channel photomultiplier tubes. Interaction of the scintillation light with the phosphor coating changes the pulse shape in a depth-dependent manner. 3 x 3 x 10 mm(3) LSO scintillation crystals with polished surfaces were characterized, with and without phosphor coating, to assess DOI capability and timing properties. Two different phosphor coating geometries were studied: coating of the top surface of the crystal, and the top plus half of the crystal sides. There was negligible depth dependency in the decay time when coating only the top surface, however there was a similar to 10 ns difference in end-to-end decay time when coating the top plus half of the crystal sides, sufficient to support the use of three DOI bins (3.3 mm DOI bin width). The rise time of the half-coated phosphor crystal was slightly faster at all depths, compared to uncoated crystals, however the signal amplitude was lower. Phosphor coating resulted in depth-dependent photopeak positions with an energy resolution of 13.7%, at a depth of 1 mm, and 15.3%, at a depth of 9 mm, for the half-coated crystal. Uncoated LSO crystals showed no change in photopeak position as a function of depth, with an energy resolution of 10.4%. The head-on coincidence timing resolution (CTR) of two uncoated LSO crystals was 287 ps using constant fraction discrimination for time pick-off. With phosphor coating, the CTR of the top-coated crystal was 314 ps, compared to 384 ps for the half-coated crystal. We demonstrate that the trade-off between timing resolution and DOI resolution can be controlled by the phosphor coating geometry. Here we present preliminary results demonstrating that good DOI resolution can be achieved with only a modest 26% degradation in CTR.