Department of Biomedical Engineering, University of California-Davis, Davis, California
Department of Radiology, University of California-Davis, Davis, California.
J Nucl Med. 2021 Jun 1;62(6):861-870. doi: 10.2967/jnumed.120.250597. Epub 2020 Oct 2.
The world's first total-body PET scanner with an axial field of view (AFOV) of 194 cm is now in clinical and research use at our institution. The uEXPLORER PET/CT system is the first commercially available total-body PET scanner. Here we present a detailed physical characterization of this scanner based on National Electrical Manufacturers Association (NEMA) NU 2-2018 along with a new set of measurements devised to appropriately characterize the total-body AFOV. Sensitivity, count-rate performance, time-of-flight resolution, spatial resolution, and image quality were evaluated following the NEMA NU 2-2018 protocol. Additional measurements of sensitivity and count-rate capabilities more representative of total-body imaging were performed using extended-geometry phantoms based on the world-average human height (∼165 cm). Lastly, image quality throughout the long AFOV was assessed with the NEMA image quality (IQ) phantom imaged at 5 axial positions and over a range of expected total-body PET imaging conditions (low dose, delayed imaging, short scan duration). Our performance evaluation demonstrated that the scanner provides a very high sensitivity of 174 kcps/MBq, a count-rate performance with a peak noise-equivalent count rate of approximately 2 Mcps for total-body imaging, and good spatial resolution capabilities for human imaging (≤3.0 mm in full width at half maximum near the center of the AFOV). Excellent IQ, excellent contrast recovery, and low noise properties were illustrated across the AFOV in both NEMA IQ phantom evaluations and human imaging examples. In addition to standard NEMA NU 2-2018 characterization, a new set of measurements based on extending NEMA NU 2-2018 phantoms and experiments was devised to characterize the physical performance of the first total-body PET system. The rationale for these extended measurements was evident from differences in sensitivity, count-rate-activity relationships, and noise-equivalent count-rate limits imposed by differences in dead time and randoms fraction between the NEMA NU 2 70-cm phantoms and the more representative total-body imaging phantoms. Overall, the uEXPLORER PET system provides ultra-high sensitivity that supports excellent spatial resolution and IQ throughout the field of view in both phantom and human imaging.
世界上首款轴向视野（AFOV）为 194cm 的全身 PET 扫描仪现已在本机构投入临床和科研使用。uEXPLORER PET/CT 系统是首款商业化的全身 PET 扫描仪。在此，我们根据美国电器制造商协会（NEMA）NU 2-2018 标准对该扫描仪进行了详细的物理特性描述，并设计了一组新的测量方法，以适当描述全身 AFOV。根据 NEMA NU 2-2018 协议，我们对灵敏度、计数率性能、飞行时间分辨率、空间分辨率和图像质量进行了评估。使用基于世界平均人体高度（约 165cm）的扩展几何形状的体模，对灵敏度和更能代表全身成像的计数率性能进行了额外的测量。最后，使用 NEMA 图像质量（IQ）体模在 5 个轴向位置和一系列预期的全身 PET 成像条件（低剂量、延迟成像、短扫描时间）下对整个长 AFOV 的图像质量进行了评估。我们的性能评估表明，该扫描仪提供了非常高的灵敏度（174kcps/MBq）、用于全身成像的峰值噪声等效计数率（约 2Mcps）的计数率性能以及用于人体成像的良好空间分辨率能力（在 AFOV 中心附近≤3.0mm 的全宽半最大值）。在 NEMA IQ 体模评估和人体成像实例中，整个 AFOV 均展示了出色的 IQ、出色的对比度恢复和低噪声特性。除了标准的 NEMA NU 2-2018 特性描述外，还设计了一组基于扩展 NEMA NU 2-2018 体模和实验的新测量方法，以对首款全身 PET 系统的物理性能进行描述。这些扩展测量的基本原理是基于 NEMA NU 2 70cm 体模与更具代表性的全身成像体模之间的死时间和随机分数差异导致的灵敏度、计数率-活性关系和噪声等效计数率限制的差异。总的来说，uEXPLORER PET 系统提供了超高的灵敏度，可在体模和人体成像中在整个视场中提供出色的空间分辨率和 IQ。
