Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211 Geneva, Switzerland.
Phys Med Biol. 2011 Oct 21;56(20):6649-64. doi: 10.1088/0031-9155/56/20/009. Epub 2011 Sep 23.
The objective of this study is to characterize the performance of the preclinical avalanche photodiode (APD)-based LabPET-8™ subsystem of the fully integrated trimodality PET/SPECT/CT Triumph™ scanner using the National Electrical Manufacturers Association (NEMA) NU 04-2008 protocol. The characterized performance parameters include the spatial resolution, sensitivity, scatter fraction, counts rate performance and image-quality characteristics. The PET system is fully digital using APD-based detector modules with highly integrated electronics. The detector assembly consists of phoswich pairs of Lu(1.9)Y(0.1)SiO(5) (LYSO) and Lu(0.4)Gd(1.6)SiO(5) (LGSO) crystals with dimensions of 2 × 2 × 14 mm(3) having 7.5 cm axial and 10 cm transverse field of view (FOV). The spatial resolution and sensitivity were measured using a small (22)Na point source at different positions in the scanner's FOV. The scatter fraction and count rate characteristics were measured using mouse- and rat-sized phantoms fitted with an (18)F line source. The overall imaging capabilities of the scanner were assessed using the NEMA image-quality phantom and laboratory animal studies. The NEMA-based radial and tangential spatial resolution ranged from 1.7 mm at the center of the FOV to 2.59 mm at a radial offset of 2.5 cm and from 1.85 mm at the center of the FOV to 1.76 mm at a radial offset of 2.5 cm, respectively. Iterative reconstruction improved the spatial resolution to 0.84 mm at the center of the FOV. The total absolute system sensitivity is 12.74% for an energy window of 250-650 keV. For the mouse-sized phantom, the peak noise equivalent count rate (NECR) is 183 kcps at 2.07 MBq cc(-1), whereas the peak true count rate is 320 kcps at 2.5 MBq cc(-1) with a scatter fraction of 19%. The rat-sized phantom had a scatter fraction of 31%, with a peak NECR of 67 kcps at 0.23 MBq cc(-1) and a peak true count rate of 186 kcps at 0.27 MBq cc(-1). The average activity concentration and percentage standard deviation were 126.97 kBq ml(-1) and 7%, respectively. The performance of the LabPET-8™ scanner was characterized based on the NEMA NU 04-2008 standards. The all in all performance demonstrates that the LabPET-8™ system is able to produce high-quality and highly contrasted images in a reasonable time, and as such it is well suited for preclinical molecular imaging-based research.
本研究旨在使用美国电器制造商协会（NEMA）NU 04-2008 协议，对完全集成的三模态 PET/SPECT/CT 胜利扫描仪的基于临床前雪崩光电二极管（APD）的 LabPET-8™子系统的性能进行特征描述。所描述的性能参数包括空间分辨率、灵敏度、散射分数、计数率性能和图像质量特性。该 PET 系统完全采用基于 APD 的探测器模块实现数字化，具有高度集成的电子设备。探测器组件由 Lu(1.9)Y(0.1)SiO(5)（LYSO）和 Lu(0.4)Gd(1.6)SiO(5)（LGSO）晶体的闪烁对组成，尺寸为 2×2×14mm(3)，具有 7.5cm 轴向和 10cm 横向视野（FOV）。通过在扫描仪的 FOV 中的不同位置使用小（22）Na 点源来测量空间分辨率和灵敏度。通过使用配备（18）F 线源的小鼠和大鼠大小的体模来测量散射分数和计数率特性。使用 NEMA 图像质量体模和实验室动物研究评估扫描仪的整体成像能力。基于 NEMA 的径向和切向空间分辨率范围从 FOV 中心的 1.7mm 到 2.5cm 径向偏移处的 2.59mm，以及从 FOV 中心的 1.85mm 到 2.5cm 径向偏移处的 1.76mm，分别。迭代重建将空间分辨率提高到 FOV 中心的 0.84mm。总绝对系统灵敏度为 250-650keV 能量窗口的 12.74%。对于小鼠大小的体模，在 2.07MBq cc(-1)时，峰值噪声等效计数率（NECR）为 183kcps，而在 2.5MBq cc(-1)时，真实计数率峰值为 320kcps，散射分数为 19%。大鼠大小的体模散射分数为 31%，在 0.23MBq cc(-1)时峰值 NECR 为 67kcps，在 0.27MBq cc(-1)时峰值真实计数率为 186kcps。平均活度浓度和百分比标准偏差分别为 126.97kBq ml(-1)和 7%。根据 NEMA NU 04-2008 标准对 LabPET-8™ 扫描仪的性能进行了特征描述。所有这些性能表明，LabPET-8™ 系统能够在合理的时间内生成高质量且对比度高的图像，因此非常适合基于临床前分子成像的研究。
