Zhongshan Hospital, Fudan University, 1609 Xietu Road, Shanghai, 200032, China.
Institute of Nuclear Medicine, Fudan University, Shanghai, China.
Eur J Nucl Med Mol Imaging. 2021 Jun;48(6):1726-1735. doi: 10.1007/s00259-020-05135-9. Epub 2021 Jan 3.
In this paper, we aimed to evaluate the positron emission tomography (PET) performance of, to the best of our knowledge, the third commercially available whole-body integrated PET/magnetic resonance (MR) system.
The PET system performance was measured following the NEMA standards with and without simultaneous MR operation. PET spatial resolution, sensitivity, scatter fraction, count-rate performance, accuracy of count losses and random corrections, image quality, and time-of-flight (TOF) resolution were quantitatively evaluated. Clinical scans were acquired at the PET/MR system and compared with images acquired at a PET/CT with the same digital detector technology.
Measurement results of essential PET performance were reported in the form of MR idle (MR pulsing). The axial, radial, and tangential spatial resolutions were measured as 2.72 mm (2.73 mm), 2.86 mm (2.85 mm), and 2.81 mm (2.82 mm) FWHM, respectively, at 1 cm radial offset. The NECR peak was measured as 129.2 kcps (129.5 kcps) at 14.7 kBq mL (14.2 kBq mL). The scatter fraction at NECR peak was 37.9% (36.5%), and the maximum slice error below NECR was 4.1% (4.5%). Contrast recovery coefficients ranged from 51.8% (52.3%) for 10 mm hot sphere to 87.3% (87.2%) for 37 mm cold sphere. TOF resolution at 5.3 kBq mL was measured at 535 ps (540 ps). With point source, TOF was measured to be 474 ps (485 ps). Clinical scans revealed similar image quality from the PET/MR and the comparative PET/CT system.
The PET performance of the newly introduced integrated PET/MR system is not significantly affected by the simultaneous operation of an MR sequence (2-point DIXON sequence). Measurement results demonstrate comparable performance with other state-of-the-art PET/MR systems. The clinical benefits of high spatial resolution and long axial coverage remain to be further evaluated in specific clinical imaging applications.
在本文中，我们旨在评估我们所知的第三款商用全身集成正电子发射断层扫描（PET）/磁共振（MR）系统的 PET 性能。
根据 NEMA 标准，在有和没有同时进行 MR 操作的情况下对 PET 系统性能进行了测量。定量评估了 PET 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、图像质量和飞行时间（TOF）分辨率。在 PET/MR 系统上采集临床扫描，并与具有相同数字探测器技术的 PET/CT 采集的图像进行比较。
以 MR 空闲（MR 脉冲）的形式报告了基本 PET 性能的测量结果。在 1 cm 径向偏移处，轴向、径向和切向空间分辨率分别测量为 2.72mm（2.73mm）、2.86mm（2.85mm）和 2.81mm（2.82mm）FWHM。在 14.7 kBq·mL（14.2 kBq·mL）时，NECR 峰值测量为 129.2 kcps（129.5 kcps）。NECR 峰值时的散射分数为 37.9%（36.5%），低于 NECR 的最大切片误差为 4.1%（4.5%）。对比恢复系数范围为 10mm 热球 51.8%（52.3%）至 37mm 冷球 87.3%（87.2%）。在 5.3 kBq·mL 时测量的 TOF 分辨率为 535 ps（540 ps）。使用点源时，TOF 测量值为 474 ps（485 ps）。临床扫描显示，来自新引入的集成 PET/MR 系统的 PET 图像质量与比较的 PET/CT 系统相似。
新引入的集成 PET/MR 系统的 PET 性能受同时进行的 MR 序列（2 点 Dixon 序列）的影响不大。测量结果表明，与其他最先进的 PET/MR 系统具有相当的性能。高空间分辨率和长轴向覆盖的临床优势有待在特定的临床成像应用中进一步评估。
