Department of Radiology, Division of Nuclear Medicine, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115, USA.
Med Phys. 2010 Jul;37(7):3660-6. doi: 10.1118/1.3455705.
The purpose of this study was to evaluate the variability in quantitation of positron emission tomography (PET) data acquired within the context of a multicenter consortium.
PET quantitation phantoms designed by American Association of Physicists in Medicine/ Society of Nuclear Medicine Task Group 145 were sent to the ten member sites of the Pediatric Brain Tumor Consortium (PBTC), a NIH-funded research consortium investigating the biology and therapies for brain tumors in children. The phantoms were water-filled cylinders (18.6 cm inside height and 20.4 cm inside diameter) based on the standard ACR phantom with four small, "hot" cylinders of varying diameters (8, 12, 16, 25 mm, all with 38 mm height), consisting of an equilibrium mixture of 68Ge/68Ga in an epoxy matrix. At each site, the operator added the appropriate amount of 18F to the water in the background in order to attain a feature-to-background ratio of roughly 4:1. The phantom was imaged and reconstructed as if it were a brain PET scan for the PBTC. An approximately 12 mm circular region of interest (ROI) was placed over each feature and in a central area in the background. The mean and maximum pixel values for each ROI were requested from local sites in units of activity concentration (Bq/ml) and the standard uptake value (SUV) (g/mL) based on bodyweight. The activity concentration was normalized by the decay-corrected known activity concentration for the features, and reported as the absolute recovery coefficient (RC). In addition, central analyses were performed by two observers
The ten sites successfully imaged the phantom within 5 months and submitted the quantitative results and the phantom image data to the PBTC Operations and Biostatistics Center. The local site-based and central analyses yielded similar mean values for RC. Local site-based SUV measurements of the hot cylindrical features yielded greater variability than central analysis (COV range of 29.9%-42.8% compared to 7.7%-23.2%). Correcting for miscalculations in the local site reported SUVs substantially reduced the variation to levels similar to the central analysis (COV range of 8.8%-18.4%) and also led to the local sites providing a similar mean of the SUV values to those from the central analysis. In the central analysis, the use of mean SUV in place of maximum SUV for an ROI of fixed size substantially reduced the variation in the SUV values (COV ranges of 7.7%-11.3% vs. 9.3%-23.2%).
Based on this investigation, a SUV variability in the range of 10%-25% due solely to instrument and analysis factors can be expected in the context of a multicenter consortium if a central reading is used and quality assurance and quality control procedures are followed. The overall SUV variability can be expected to be larger than this due to biological and protocol factors.
本研究旨在评估在多中心研究联盟背景下进行正电子发射断层扫描（PET）数据定量的可变性。
由美国医学物理学家协会/核医学协会任务组 145 设计的 PET 定量体模被发送到儿科脑肿瘤联盟（PBTC）的十个成员站点，这是一个由美国国立卫生研究院资助的研究联盟，旨在研究儿童脑肿瘤的生物学和治疗方法。体模是基于标准 ACR 体模的充满水的圆柱体（内高 18.6 厘米，内径 20.4 厘米），有四个不同直径的小“热”圆柱体（8、12、16、25 毫米，均高 38 毫米），由环氧树脂基质中的 68Ge/68Ga 平衡混合物组成。在每个站点，操作员在背景水中添加适量的 18F，以使特征与背景的比率大致为 4:1。该体模被成像并重建为 PBTC 的脑 PET 扫描。在每个特征和背景中央的大约 12 毫米圆形感兴趣区（ROI）中放置一个 ROI。从当地站点以活性浓度（Bq/ml）和标准摄取值（SUV）（g/ml）为单位请求每个 ROI 的平均和最大像素值，基于体重。活性浓度通过对特征的衰减校正已知活性浓度进行归一化，并报告为绝对恢复系数（RC）。此外，由两名观察者进行中心分析。
十个站点在 5 个月内成功地对体模成像，并向 PBTC 运营和生物统计学中心提交了定量结果和体模图像数据。本地站点和中央分析的 RC 均值相似。本地站点基于 SUV 测量的热圆柱形特征的变异性大于中央分析（COV 范围为 29.9%-42.8%，而 7.7%-23.2%）。对本地站点报告的 SUV 中错误计算的校正大大降低了变化，使其与中央分析水平相似（COV 范围为 8.8%-18.4%），并使本地站点提供与中央分析相似的 SUV 值平均值。在中央分析中，对于固定大小的 ROI，使用平均 SUV 代替最大 SUV，可大大降低 SUV 值的变化（COV 范围为 7.7%-11.3%与 9.3%-23.2%）。
根据这项研究，如果使用中央读取并遵循质量保证和质量控制程序，则可以预期在多中心研究联盟背景下，由于仪器和分析因素引起的 SUV 变化在 10%-25%范围内。由于生物学和方案因素，整体 SUV 变化可能会更大。
