Department of Radiology, University of California Davis, Sacramento, California;
Department of Nuclear Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
J Nucl Med. 2024 Jul 1;65(7):1101-1106. doi: 10.2967/jnumed.124.267521.
Our aim was to define a lower limit of reduced injected activity in delayed [F]FDG total-body (TB) PET/CT in pediatric oncology patients. In this single-center prospective study, children were scanned for 20 min with TB PET/CT, 120 min after intravenous administration of a 4.07 ± 0.49 MBq/kg dose of [F]FDG. Five randomly subsampled low-count reconstructions were generated using ¼, ⅛, [Formula: see text], and [Formula: see text] of the counts in the full-dose list-mode reference standard acquisition (20 min), to simulate dose reduction. For the 2 lowest-count reconstructions, smoothing was applied. Background uptake was measured with volumes of interest placed on the ascending aorta, right liver lobe, and third lumbar vertebra body (L3). Tumor lesions were segmented using a 40% isocontour volume-of-interest approach. Signal-to-noise ratio, tumor-to-background ratio, and contrast-to-noise ratio were calculated. Three physicians identified malignant lesions independently and assessed the image quality using a 5-point Likert scale. In total, 113 malignant lesions were identified in 18 patients, who met the inclusion criteria. Of these lesions, 87.6% were quantifiable. Liver SUV did not change significantly, whereas a lower signal-to-noise ratio was observed in all low-count reconstructions compared with the reference standard ( < 0.0001) because of higher noise rates. Tumor uptake (SUV), tumor-to-background ratio, and total lesion count were significantly lower in the reconstructions with [Formula: see text] and [Formula: see text] of the counts of the reference standard ( < 0.001). Contrast-to-noise ratio and clinical image quality were significantly lower in all low-count reconstructions than with the reference standard. Dose reduction for delayed [F]FDG TB PET/CT imaging in children is possible without loss of image quality or lesion conspicuity. However, our results indicate that to maintain comparable tumor uptake and lesion conspicuity, PET centers should not reduce the injected [F]FDG activity below 0.5 MBq/kg when using TB PET/CT in pediatric imaging at 120 min after injection.
我们的目的是定义儿科肿瘤患者延迟[F]FDG 全身（TB）PET/CT 中降低注射活性的下限。在这项单中心前瞻性研究中，儿童在静脉注射 4.07±0.49 MBq/kg[F]FDG 后 120 分钟，进行 TB PET/CT 扫描。使用四分之一、八分之一、[公式：见正文]和[公式：见正文]的全剂量列表模式参考标准采集（20 分钟）中的计数，生成五个随机子采样低计数重建，以模拟剂量减少。对于最低的两个计数重建，应用了平滑处理。用感兴趣体积测量背景摄取，感兴趣体积放置在升主动脉、右肝叶和第三腰椎体（L3）上。使用 40%等体积感兴趣区方法对肿瘤病变进行分割。计算信噪比、肿瘤与背景比和对比噪声比。三位医生独立识别恶性病变，并使用 5 分李克特量表评估图像质量。总共在 18 名符合纳入标准的患者中识别出 113 个恶性病变。这些病变中，87.6%是可量化的。肝 SUV 没有显著变化，而所有低计数重建的信噪比均低于参考标准（<0.0001），因为噪声率更高。与参考标准相比，所有计数的[公式：见正文]和[公式：见正文]重建中，肿瘤摄取（SUV）、肿瘤与背景比和总病变计数均显著降低（<0.001）。与参考标准相比，所有低计数重建的对比噪声比和临床图像质量均显著降低。在不降低图像质量或病变可见度的情况下，延迟[F]FDG TB PET/CT 成像在儿童中可以进行剂量减少。然而，我们的结果表明，为了保持可比的肿瘤摄取和病变可见度，当在注射后 120 分钟使用 TB PET/CT 进行儿科成像时，PET 中心不应将注射的[F]FDG 活性减少到 0.5 MBq/kg 以下。
