A prototype axial shield for use in 3D whole-body PET
A prototype axial shield for use in 3D whole-body PET
复制标题
用于 3D 全身 PET 的原型轴向护罩
DOI：
10.1109/23.910823
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发表时间：
2001
影响因子：
1.8
通讯作者：
R. Laforest
中科院分区：
文献类型：
--
作者：
P. Cutler;R. Laforest
在 3D PET 测量中，已知直接视场 (FOV) 之外的活动会降低直接 FOV 内的信噪比，主要是通过增加随机重合的总体率。在 3D 大脑研究中，在患者周围使用额外的屏蔽来解决这个问题。额外的屏蔽限制了对直接视场（单视场）上方和下方区域产生的单光子的接受，从而减少了断层扫描仪测量的随机性。在这项工作中，作者将这一想法扩展到躯干，采用屏蔽配置，该屏蔽配置由两个“蛤壳”铅屏蔽组成，围绕患者的轴向视场上方和下方。导线厚度为 6 毫米，轴向长度为 10 或 20 厘米，并弯曲成 C 形，以贴合模型或患者的躯干。蛤壳式的上半部分放置在塑料轮上，这些轮子在安装在患者托盘边缘的轨道上行驶，每个防护罩的单独下半部分放置在床下的聚苯乙烯泡沫塑料支架上。防护罩放置在直接视野的上方和下方，并尽可能靠近患者。噪声当量计数 (NEC) 曲线是在轴向长圆柱形模型周围有或没有屏蔽的情况下测量的。计算 2D 和 3D 患者研究的 NEC 率，并与模型导出的 NEC 曲线进行比较，以确定轴向屏蔽的有效性。作者发现，在全身 FDG 研究的标称活动范围的高端，额外的屏蔽对体模 NEC 提供了小幅改善。两名患者的 3D 采集产生大约两倍的 NEC 优势。通过添加轴向屏蔽，在此活动范围的高端可能会有小的额外改进。
In 3D PET measurements, activity outside of the direct field of-view (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, additional shielding around the patient has been used to address this issue. The additional shielding limits the acceptance of single-photons arising from regions just above and below the direct FOV, the singles FOV, and thereby reduces the randoms measured by the tomograph. In this work, the authors 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 clam-shell rests on plastic wheels which travel on rails mounted to the edge of the patient pallet, and the separate lower half of each shield rests on a Styrofoam support beneath the bed. The shields are placed just above and below 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 calculated and compared with the phantom-derived NEC curves to determine the effectiveness of the axial shields. The authors find that the additional shielding offers a small improvement in phantom NEC at the high end of the nominal activity range for whole body FDG studies. 3D acquisition in two patients produces an NEC advantage of approximately a factor of two. With the addition of an axial shield, there may be a small additional improvement at the high end of this activity range.