Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Med Phys. 2011 May;38(5):2629-38. doi: 10.1118/1.3578604.
The standardized uptake value (SUV) is a quantitative measure of FDG tumor uptake frequently used as a tool to monitor therapeutic response. This study aims to (i) assess the reproducibility and uncertainty of SUV max and SUV mean, due to purely statistical, i.e., nonbiological, effects and (ii) to establish the minimum uncertainty below which changes in SUV cannot be expected to be an indicator of physiological changes.
Three sets of measurements were made using a GE Discovery STE PET/CT Scanner in 3D mode: (1) A uniform 68Ge 20 cm diameter cylindrical phantom was imaged. Thirty serial frames were acquired for durations of 3, 6, 10, 15, and 30 min. (2) Esser flangeless phantom (Data Spectrum, approximately 6.1 L) with fillable thin-walled cylinders inserts (diameters: 8, 12, 16, and 25 mm; height: approximately 3.8 mm) was scanned for five consecutive 3 min runs. The cylinders were filled with 18FDG with a 37 kBq/cc concentration, and with a target-to-background ratio (T/BKG) of 3/1. (3) Eight cancer patients with healthy livers were scanned approximately 1.5 h post injection. Three sequential 3 min scans were performed for one bed position covering the liver, with the patient and bed remaining at the same position for the entire length of the scan. Volumes of interest were drawn on all images using the corresponding CT and then transferred to the PET images. For each study (1-3), the average percent change in SUV mean and SUV max were determined for each run pair. Moreover, the repeatability coefficient was calculated for both the SUV mean and SUV max for each pair of runs. Finally, the overall ROI repeatability coefficient was determined for each pair of runs.
For the 68Ge phantom the average percent change in SUV max and SUV mean decrease as a function of increasing acquisition time from 4.7 +/- 3.1 to 1.1 +/- 0.6%, and from 0.14 +/- 0.09 to 0.04 +/- 0.03%, respectively. Similarly, the coefficients of repeatability also decrease between the 3 and 30 min acquisition scans, in the range of 10.9 +/- 3.9% - 2.6 +/- 0.9%, and 0.3 +/- 0.1% - 0.10 +/- 0.04%, for the SUV max and SUV mean, respectively. The overall ROI repeatability decreased from 18.9 +/- 0.2 to 6.0 +/- 0.1% between the 3 and 30 min acquisition scans. For the l8FDG phantom, the average percent change in SUV max and SUV mean decreases with target diameter from 3.6 +/- 2.0 to 1.5 +/- 0.8% and 1.5 +/- 1.3 to 0.26 +/- 0.15%, respectively, for targets from 8-25 mm in diameter and for a region in the background (BKG). The coefficients of repeatability for SUV max and SUV mean also decrease as a function of target diameter from 7.1 +/- 2.5 to 2.4 +/- 0.9 and 4.2 +/- 1.5 to 0.6 +/- 0.2, respectively, for targets from 8 mm to BKG in diameter. Finally, overall ROI repeatability decreased from 12.0 +/- 4.1 to 13.4 +/- 0.5 targets from 8 mm to BKG in diameter. Finally, for the measurements in healthy livers the average percent change in SUVmax and SUV mean were in the range of 0.5 +/- 0.2% - 6.2 +/- 3.9% and 0.4 +/- 0.1 and 1.6 +/- 1%, respectively. The coefficients of repeatability for SUV max and SUV men are in the range of 0.6 +/- 0.7% - 9.5 +/- 12% and 0.6 +/- 0.7% - 2.9 +/- 3.6%, respectively. The overall target repeatability varied between 27.9 +/- 0.5% and 41.1 +/- 1.0%.
The statistical fluctuations of the SUV mean are half as large as those of the SUV max in the absence of biological or physiological effects. In addition, for clinically applicable scan durations (i.e., approximately 3 min) and FDG concentrations, the SUV max and SUV mean have similar amounts of statistical fluctuation for small regions. However, the statistical fluctuations of the SUVmean rapidly decrease with respect tothe SUVmax as the statistical power of the data grows either due to longer scanning times or as the target regions encompass a larger volume.
标准化摄取值（SUV）是一种常用于监测治疗反应的 FDG 肿瘤摄取的定量测量方法。本研究旨在：（i）评估由于纯粹的统计，即非生物学效应引起的 SUVmax 和 SUVmean 的可重复性和不确定性；（ii）确定 SUV 变化不可能指示生理变化的最小不确定性。
使用 GE Discovery STE PET/CT 扫描仪在 3D 模式下进行了三组测量：（1）均匀的 68Ge 20cm 直径圆柱状体模，采集 3、6、10、15 和 30min 的 30 个连续帧。（2）Esser 无边缘体模（Data Spectrum，约 6.1L），可填充薄壁圆柱插入物（直径：8、12、16 和 25mm；高度：约 3.8mm），连续进行五次 3min 扫描。圆柱体用 18FDG 填充，浓度为 37kBq/cc，目标与背景的比值（T/BKG）为 3/1。（3）八名健康肝脏的癌症患者，注射后约 1.5 小时进行扫描。对一个肝区的三个连续 3min 扫描进行了 3 次扫描，患者和床在整个扫描过程中保持在同一位置。使用相应的 CT 在所有图像上绘制感兴趣区域（ROI），然后将其转移到 PET 图像上。对于每个研究（1-3），确定了每个运行对的 SUVmean 和 SUVmax 的平均百分比变化。此外，还计算了每个运行对的 SUVmean 和 SUVmax 的重复性系数。最后，确定了每个运行对的整体 ROI 重复性系数。
对于 68Ge 体模，SUVmax 和 SUVmean 的平均百分比变化随着采集时间的增加而降低，从 4.7%±3.1%降低至 1.1%±0.6%，从 0.14%±0.09%降低至 0.04%±0.03%。同样，在 3 和 30min 采集扫描之间，SUVmax 和 SUVmean 的重复性系数也分别在 10.9%±3.9%-2.6%±0.9%和 0.3%±0.1%-0.10%±0.04%的范围内降低。在 3 和 30min 采集扫描之间，整体 ROI 重复性从 18.9%±0.2%降低至 6.0%±0.1%。对于 18FDG 体模，SUVmax 和 SUVmean 的平均百分比变化随着目标直径的减小而降低，从 8-25mm 直径的目标的 3.6%±2.0%降低至 1.5%±0.8%，从 1.5%±1.3%降低至 0.26%±0.15%，对于背景（BKG）区域。SUVmax 和 SUVmean 的重复性系数也随着目标直径的减小而降低，从 8mm 目标的 7.1%±2.5%降低至 2.4%±0.9%和 4.2%±1.5%降低至 0.6%±0.2%，对于 BKG 区域。最后，整体 ROI 重复性从 12.0%±4.1%降低至 13.4%±0.5%，从 8mm 目标到 BKG 区域。最后，在健康肝脏的测量中，SUVmax 和 SUVmean 的平均百分比变化在 0.5%±0.2%-6.2%±3.9%和 0.4%±0.1%和 1.6%±1%的范围内。SUVmax 和 SUVmean 的重复性系数在 0.6%±0.7%-9.5%±12%和 0.6%±0.7%-2.9%±3.6%的范围内。整体目标重复性在 27.9%±0.5%和 41.1%±1.0%之间变化。
在不存在生物学或生理学效应的情况下，SUVmean 的统计波动是 SUVmax 的一半。此外，对于临床可应用的扫描时间（即大约 3min）和 FDG 浓度，对于小区域，SUVmax 和 SUVmean 具有相似数量的统计波动。然而，随着数据统计能力的提高，即由于扫描时间的延长或目标区域的体积增大，SUVmean 的统计波动相对于 SUVmax 迅速减小。
