Division of Nuclear Medicine, Geneva University Hospital, Geneva, Switzerland.
J Nucl Med. 2010 Oct;51(10):1608-15. doi: 10.2967/jnumed.110.076125. Epub 2010 Sep 16.
The purpose of this work was to evaluate the performance characteristics of the preclinical X-PET subsystem of the FLEX Triumph PET/CT scanner based on the NU 4-2008 standards of the National Electrical Manufacturers Association (NEMA).
The performance parameters evaluated include the spatial resolution, scatter fraction, count losses and random coincidences, sensitivity, and image-quality characteristics. The PET detector array consisted of 11,520 individual bismuth germanate crystals arranged in 48 rings and 180 blocks, with an axial field of view (FOV) of 11.6 cm and a inner ring diameter of 16.5 cm. The spatial resolution was measured with a small (22)Na point source (diameter, 0.25 mm) at different radial offsets from the center. Sensitivity was calculated using the same source by stepping the source axially through the axial FOV of the scanner. Scatter fraction and counting-rate performances were determined using a mouse- and rat-sized phantom with an (18)F line source insert. The NEMA image-quality phantom and rodent imaging were also performed to access the overall imaging capabilities of the scanner.
Tangential spatial resolution in terms of full width at half maximum varied between 2.2 mm at the center of the FOV and 2.3 mm at a radial offset of 2.5 cm. The radial spatial resolution varied between 2.0 at the center and 4.4 mm at a radial offset of 2.3 cm. The peak system absolute sensitivity was 5.9% at the center of the FOV. The absolute system sensitivity was 0.67 counts/s/Bq, and the relative total system sensitivity was 73.9%. The scatter fraction for the mouse-sized phantom was 7.9%, with a peak true counting rate of 168 kilocounts per second (kcps) at 0.3 MBq/mL and a peak noise-equivalent counting rate of 106 kcps at 0.17 MBq/mL. The rat-sized phantom had a scatter fraction of 21%, with a peak true counting rate of 93 kcps at 0.034 MBq/mL and a peak noise-equivalent counting rate of 49 kcps at 0.02 MBq/mL. Recovery coefficients for the image-quality phantom ranged from 0.13 to 0.88.
The performance of the X-PET scanner based on the NEMA NU 4-2008 standards was fully characterized. The overall performance demonstrates that the X-PET system is suitable for preclinical research.
本研究旨在根据美国电器制造商协会（NEMA）的 NU 4-2008 标准，评估 FLEX Triumph PET/CT 扫描仪的 X-PET 子系统的临床前性能特征。
评估的性能参数包括空间分辨率、散射分数、计数损失和随机符合、灵敏度以及图像质量特征。PET 探测器阵列由 11520 个单独的锗酸铋晶体组成，排列在 48 个环和 180 个块中，轴向视野（FOV）为 11.6 cm，内圈直径为 16.5 cm。空间分辨率通过在不同的径向偏移处从中心测量一个小的（22）Na 点源（直径 0.25mm）来测量。通过沿轴向穿过扫描仪的轴向 FOV 移动源，使用相同的源计算灵敏度。使用带有（18）F 线源插入物的小鼠和大鼠大小的体模确定散射分数和计数率性能。还进行了 NEMA 图像质量体模和啮齿动物成像，以评估扫描仪的整体成像能力。
在 FOV 中心处，切线空间分辨率的半最大值全宽在 2.2mm 到 2.5cm 处的径向偏移处的 2.3mm 之间变化。径向空间分辨率在中心处为 2.0，在 2.3cm 处的径向偏移处为 4.4mm。系统的绝对灵敏度峰值为 FOV 中心处的 5.9%。系统的绝对灵敏度为 0.67 计数/s/Bq，相对总系统灵敏度为 73.9%。在小鼠大小的体模中，散射分数为 7.9%，在 0.3MBq/mL 时的峰值真实计数率为 168 千计数/秒（kcps），在 0.17MBq/mL 时的峰值噪声等效计数率为 106 kcps。大鼠大小的体模的散射分数为 21%，在 0.034MBq/mL 时的峰值真实计数率为 93 kcps，在 0.02MBq/mL 时的峰值噪声等效计数率为 49 kcps。图像质量体模的恢复系数范围为 0.13 到 0.88。
根据 NEMA NU 4-2008 标准，对 X-PET 扫描仪的性能进行了全面表征。整体性能表明，X-PET 系统适用于临床前研究。
