Department of Radiology & Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands.
Faculty of Medical Sciences, Nuclear Medicine and Molecular Imaging, Hanzeplein 1, 9713 GZ, Groningen, The Netherlands.
Med Phys. 2017 Dec;44(12):6413-6424. doi: 10.1002/mp.12623. Epub 2017 Nov 19.
In longitudinal oncological and brain PET/CT studies, it is important to understand the repeatability of quantitative PET metrics in order to assess change in tracer uptake. The present studies were performed in order to assess precision as function of PET/CT system, reconstruction protocol, analysis method, scan duration (or image noise), and repositioning in the field of view.
Multiple (repeated) scans have been performed using a NEMA image quality (IQ) phantom and a 3D Hoffman brain phantom filled with F solutions on two systems. Studies were performed with and without randomly (< 2 cm) repositioning the phantom and all scans (12 replicates for IQ phantom and 10 replicates for Hoffman brain phantom) were performed at equal count statistics. For the NEMA IQ phantom, we studied the recovery coefficients (RC) of the maximum (SUV ), peak (SUV ), and mean (SUV ) uptake in each sphere as a function of experimental conditions (noise level, reconstruction settings, and phantom repositioning). For the 3D Hoffman phantom, the mean activity concentration was determined within several volumes of interest and activity recovery and its precision was studied as function of experimental conditions.
The impact of phantom repositioning on RC precision was mainly seen on the Philips Ingenuity PET/CT, especially in the case of smaller spheres (< 17 mm diameter, P < 0.05). This effect was much smaller for the Siemens Biograph system. When exploring SUV , SUV , or SUV of the spheres in the NEMA IQ phantom, it was observed that precision depended on phantom repositioning, reconstruction algorithm, and scan duration, with SUV being most and SUV least sensitive to phantom repositioning. For the brain phantom, regional averaged SUVs were only minimally affected by phantom repositioning (< 2 cm).
The precision of quantitative PET metrics depends on the combination of reconstruction protocol, data analysis methods and scan duration (scan statistics). Moreover, precision was also affected by phantom repositioning but its impact depended on the data analysis method in combination with the reconstructed voxel size (tissue fraction effect). This study suggests that for oncological PET studies the use of SUV may be preferred over SUV because SUV is less sensitive to patient repositioning/tumor sampling.
在纵向肿瘤学和脑部 PET/CT 研究中，了解定量 PET 指标的可重复性对于评估示踪剂摄取的变化非常重要。本研究旨在评估 PET/CT 系统、重建方案、分析方法、扫描时长（或图像噪声）以及在视野内重新定位对精度的影响。
在两个系统上，使用 NEMA 图像质量（IQ）体模和充满 F 溶液的 3D Hoffman 脑体模进行了多次（重复）扫描。研究在体模随机（<2cm）重新定位和不重新定位的情况下进行，所有扫描（IQ 体模 12 个重复，Hoffman 脑体模 10 个重复）均在相同的计数统计量下进行。对于 NEMA IQ 体模，我们研究了每个球体的最大（SUV ）、峰值（SUV ）和平均（SUV ）摄取的恢复系数（RC）作为实验条件（噪声水平、重建设置和体模重新定位）的函数。对于 3D Hoffman 体模，在几个感兴趣体积内确定了平均活性浓度，并研究了其作为实验条件函数的活性恢复及其精度。
体模重新定位对 RC 精度的影响主要见于飞利浦 Ingenuity PET/CT，尤其是在较小球体（<17mm 直径，P<0.05）的情况下。对于西门子 Biograph 系统，这种影响要小得多。在 NEMA IQ 体模中研究球体的 SUV 、SUV 或 SUV 时，观察到精度取决于体模重新定位、重建算法和扫描时长，其中 SUV 对体模重新定位最敏感，SUV 最不敏感。对于脑体模，区域平均 SUV 仅受体模重新定位的轻微影响（<2cm）。
定量 PET 指标的精度取决于重建方案、数据分析方法和扫描时长（扫描统计量）的组合。此外，精度还受体模重新定位的影响，但影响取决于数据分析方法与重建体素大小的组合（组织分数效应）。本研究表明，对于肿瘤学 PET 研究，使用 SUV 可能优于 SUV ，因为 SUV 对患者重新定位/肿瘤取样的敏感性较低。
