Schöder Heiko, Erdi Yusuf E, Chao Kenneth, Gonen Mithat, Larson Steven M, Yeung Henry W D
Department of Radiology/Nuclear Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York, USA.
J Nucl Med. 2004 Apr;45(4):559-66.
The standardized uptake value (SUV) is the most commonly used parameter to quantify the intensity of radiotracer uptake in tumors. Previous studies suggested that measurements of (18)F-FDG accumulation in tissue might be affected by the image reconstruction method, but the clinical relevance of these findings has not been assessed.
Phantom studies were performed and clinical whole-body (18)F-FDG PET images of 85 cancer patients were analyzed. All images were reconstructed using either filtered backprojection (FBP) with measured attenuation correction (MAC) or iterative reconstruction (IR) with segmented attenuation correction (SAC). In a subset of 15 patients, images were reconstructed using all 4 combinations of IR+SAC, IR+MAC, FBP+SAC, and FBP+MAC. For phantom studies, a sphere containing (18)F-FDG was placed in a water-filled cylinder and the activity concentration of that sphere was measured in FBP and IR reconstructed images using all 4 combinations. Clinical studies were displayed simultaneously and identical regions of interest (ROIs, 50 pixels) were placed in liver, urinary bladder, and tumor tissue in both image sets. SUV max (maximal counts per pixel in ROI) and SUV avg (average counts per pixel) were measured.
In phantom studies, measurements from FBP images underestimated the true activity concentration to a greater degree than those from IR images (20% vs. 5% underestimation). In patient studies, SUV derived from FBP images were consistently lower than those from IR images in both normal and tumor tissue: Tumor SUV max with IR+SAC was 9.6 +/- 4.5, with IR+MAC it was 7.7 +/- 3.5, with FBP+MAC it was 6.9 +/- 3.0, and with FBP+SAC it was 8.6 +/- 4.1 (all P < 0.01 vs. IR+SAC). Compared with IR+SAC, SUV from FBP+MAC images were 25%-30% lower. Similar discrepancies were noted for liver and bladder. Discrepancies between measurements became more apparent with increasing (18)F-FDG concentration in tissue.
SUV measurements in whole-body PET studies are affected by the applied methods for both image reconstruction and attenuation correction. This should be considered when serial PET studies are done in cancer patients. Moreover, if SUV is used for tissue characterization, different cutoff values should be applied, depending on the chosen method for image reconstruction and attenuation correction.
标准化摄取值（SUV）是用于量化肿瘤中放射性示踪剂摄取强度的最常用参数。先前的研究表明，组织中（18）F-FDG 积聚的测量可能受图像重建方法的影响，但这些发现的临床相关性尚未得到评估。
进行了体模研究，并分析了 85 例癌症患者的临床全身（18）F-FDG PET 图像。所有图像均使用带测量衰减校正（MAC）的滤波反投影（FBP）或带分段衰减校正（SAC）的迭代重建（IR）进行重建。在 15 例患者的子集中，使用 IR+SAC、IR+MAC、FBP+SAC 和 FBP+MAC 的所有 4 种组合重建图像。对于体模研究，将一个含有（18）F-FDG 的球体置于充满水的圆柱体中，并使用所有 4 种组合在 FBP 和 IR 重建图像中测量该球体的活度浓度。同时展示临床研究图像，并在两组图像的肝脏、膀胱和肿瘤组织中放置相同的感兴趣区（ROI，50 像素）。测量 SUV max（ROI 中每像素的最大计数）和 SUV avg（每像素的平均计数）。
在体模研究中，FBP 图像的测量值比 IR 图像更严重地低估了真实活度浓度（低估 20%对 5%）。在患者研究中，FBP 图像得出的 SUV 在正常组织和肿瘤组织中均始终低于 IR 图像得出的 SUV：IR+SAC 时肿瘤 SUV max 为 9.6±4.5，IR+MAC 时为
