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首页> 外文会议>IEEE Nuclear Science Symposium >Extra shielding for improved signal-to-noise in 3D whole-body PET
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Extra shielding for improved signal-to-noise in 3D whole-body PET

机译：额外的屏蔽，用于改进3D全身宠物中的信号对噪声

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In 3D PET measurements, activity outside of the direct FOV is known to degrade signal-to-noise within the direct FOV, primarily by increasing the overall rate of random coincidences. In 3D brain studies, various configurations of additional shielding around the patient have already been successfully implemented to limit the singles field of view, and thereby reduce the randoms measured by the tomograph. In this work, we extend this idea for use in the torso with a shielding configuration consisting of two "clam-shell" shields of lead surrounding the patient both above and below the axial FOV. The lead is 6 mm thick by 10 or 20 cm in axial length, and curved into a C-shape to fit around the phantom or the patient's torso. The top half of the clamshell rests on plastic wheels which travel on two rails mounted to the edge of the patient pallet, and the lower half of each shield is fixed beneath. The shields are placed just outside the direct field of view and as close to the patient as possible. Noise Equivalent Count (NEC) curves were measured with and without shields in place around an axially long cylindrical phantom. The NEC rates from 2D and 3D patient studies were then compared with the phantom-derived NEC curves to predict the signal-to-noise gain possible by using the shields. Over the range of activity concentrations typical of whole body FDG studies, we estimate unshielded 3D offers an NEC advantage of approximately a factor of two. Our shield appears to provide only a small additional improvement at the high end of this activity range.
机译：在3D宠物测量中，已知在直接FOV之外的活动来降低直接FOV内的信号对噪声，主要通过增加随机巧合的总体速率。在3D脑研究中，已经成功地实现了患者周围的额外屏蔽的各种配置以限制单打的视野，从而减少由断层扫描测量的随机。在这项工作中，我们将这种想法扩展用于躯干的屏蔽配置，其中屏蔽配置包括两个“蛤壳”屏蔽围绕轴向FOV上方和下方的患者。铅在轴长10或20cm的引线厚，并弯曲成C形以适应幽灵或患者的躯干。蛤壳的上半部分依靠塑料轮，在安装在患者托盘边缘的两个轨道上行进，每个屏蔽的下半部分都固定在下方。屏蔽位于直接视野之外，尽可能靠近患者。用围绕轴向长的圆柱形虚拟体围绕轴向长的柱面测量噪声等价计数（NEC）曲线。然后将来自2D和3D患者研究的NEC率与幻像导出的NEC曲线进行比较，以通过使用屏蔽来预测可能的信号 - 噪声增益。在整个身体FDG研究的典型活动浓度范围内，我们估计非屏蔽3D提供了大约两倍的NEC优势。我们的盾牌似乎只提供在此活动范围的高端的额外改进。

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