The aim of this study is to conduct physical performance evaluation on the uMI550 whole-body PET/CT system according to the NEMA NU2-2018 standard. According to the NEMA NU2-2018, spatial resolution, sensitivity, scatter fraction, count-rate performance, accuracy of count losses and random corrections, image quality, and timing resolution were evaluated. Spatial resolution was measured by using a 22Na point source. System sensitivity was measured by inserting an 18F line-source in six concentric aluminum sleeves with varying diameters. Scatter fraction, count-rate performance, accuracy of count loss, and timing resolution were all calculated by analyzing dynamically acquired data of an 18F line-source inside a polyethylene cylinder in 20 cm diameter and 70 cm length. Image quality was assessed using a NEMA IEC body phantom with a 4:1 ratio of activity concentration of spheres to the warm background. Additionally, three patient studies were performed, with one brain scan and two whole-body scans, separately. The patient images were evaluated to get a visual first impression of uMI550. The tangential, radial, and axial spatial resolutions were measured as 2.91 mm, 2.98 mm, and 2.97 mm FWHM, respectively, at 1 cm radial offset. The total system sensitivity to line source at center was 10.24 cps/kBq. A NECR peak was measured as 124.4 kcps at 18.85 kBq/mL. The scatter fraction at NECR peak was 36.65%, and the maximum count-rate error at and below NEC peak was 1.55%. Contrast recovery coefficients were from 46.5 (10 mm) to 83.9% (37 mm). The timing resolution was measured as 372 ps at low count rate. NEMA NU-2 2018 testing was performed on the new SiPM-based uMI550 PET/CT system. The uMI550 shows a high-spatial resolution of less than 3 mm and a good timing resolution of 372 ps. It shows clinical significances on improving potentially diagnostic ability on small lesions.

中文翻译：

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符合NEMA NU2-2018标准的数字uMI550 PET / CT系统的性能特征。

这项研究的目的是根据NEMA NU2-2018标准对uMI550全身PET / CT系统进行物理性能评估。根据NEMA NU2-2018，评估了空间分辨率，灵敏度，散射分数，计数率性能，计数损失和随机校正的准确性，图像质量和时序分辨率。空间分辨率是通过使用22Na点源测量的。通过将18F线源插入六个直径不同的同心铝套管中来测量系统灵敏度。通过动态分析直径为20 cm，长度为70 cm的聚乙烯圆柱体内的18F线源的数据，可以计算出散射分数，计数率性能，计数损失的准确性和时序分辨率。使用NEMA IEC人体模型以4评估图像质量：球体活动浓度与温暖背景的比率为1。此外，还进行了三项患者研究，分别进行了一次脑部扫描和两次全身扫描。对患者图像进行评估以获得uMI550的视觉第一印象。径向偏移为1 cm时，切向，径向和轴向空间分辨率分别为2.91 mm，2.98 mm和2.97 mm FWHM。系统对中心线源的总灵敏度为10.24 cps / kBq。在18.85 kBq / mL下测得的NECR峰为124.4 kcps。NECR峰值处的散射分数为36.65％，NEC峰值以下的最大计数率误差为1.55％。对比度恢复系数为46.5（10毫米）至83.9％（37毫米）。在低计数率下，计时分辨率为372 ps。在新的基于SiPM的uMI550 PET / CT系统上进行了NEMA NU-2 2018测试。uMI550具有小于3 mm的高空间分辨率和372 ps的良好时序分辨率。它显示出改善潜在的小病变诊断能力的临床意义。