BACKGROUND Altered biodistribution of [F-18]2-fluoro-2-deoxyglucose (FDG) is sometimes encountered in pediatric patients undergoing chemotherapy for lymphoma on post-induction positron emission tomography (PET) imaging. A characteristic pattern of increased FDG uptake in white adipose tissue can be seen, particularly in the buccal regions, body wall and gluteal regions, with a shift of radiotracer away from the blood pool and liver. This altered biodistribution has been attributed to effects of corticosteroids in pediatric and adult patients and is important to recognize because of its potential for limiting the diagnostic quality of the PET scan and interfering with therapeutic response assessment. OBJECTIVE In contrast to the well-known metabolically active brown fat seen on up to one-third of pediatric PET scans, white fat is usually non-metabolically active. We sought to determine the incidence of altered distribution of FDG in subcutaneous white adipose tissue in pediatric patients undergoing PET imaging and to assess the association with corticosteroid use. MATERIALS AND METHODS We reviewed the medical records and imaging for four children in whom altered biodistribution in white adipose tissue was present on post-induction FDG PET/CT, identified during routine clinical practice. All four were receiving corticosteroids as part of their chemotherapy. We then retrospectively reviewed oncology FDG PET/CT scans over a 2-year period (1,361 scans in 689 patients) to determine the incidence of uptake in white fat by qualitative visual assessment. In the children identified with altered biodistribution, we measured maximum standard uptake value (SUVmax) and mean standard uptake value (SUVmean) in areas of subcutaneous white fat, the buccal regions, body wall or gluteal soft-tissue regions, liver and blood pool. We reviewed all medical records, including medication lists. We summarize the relevant clinical and imaging findings of 13 pediatric patients, including the 4 index patients. RESULTS We determined the incidence of FDG uptake in white fat to be rare, found in 9 of 1,361 (0.6%) PET scans performed for pediatric cancer evaluation. FDG uptake was increased in subcutaneous adipose tissue, particularly in the buccal regions, body wall and gluteal regions, with a shift of radiotracer away from the blood pool and liver. The degree of increased uptake in peripheral white fat varied from marked to mild, and the biodistribution was distinct from that of brown adipose tissue. Children with this altered biodistribution were uniformly receiving corticosteroids as part of induction treatment for their cancer, and these findings were only identified on post-induction PET/CT. Follow-up PET/CT documented resolution of this effect after treatment with corticosteroids ceased. CONCLUSION Our findings support the current understanding that characteristic uptake of FDG in white adipose tissue is mediated by corticosteroid effect. Although this altered biodistribution is rare (<1% of PET scans) it could impair the diagnostic quality of the scan, affecting image interpretation, and should be recognized when present.

中文翻译：

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小儿肿瘤正电子发射断层扫描（PET）/计算机断层扫描（CT）上的白色脂肪组织中18F-2-氟-2-脱氧葡萄糖的摄取。

背景技术[F-18] 2-氟-2-脱氧葡萄糖（FDG）的生物分布有时会在接受正电子发射断层扫描（PET）成像的淋巴瘤化疗的小儿患者中遇到。可以看到白色脂肪组织中FDG吸收增加的特征性模式，尤其是在颊区域，体壁和臀区域，放射性示踪剂从血池和肝脏移开。这种改变的生物分布已归因于皮质类固醇对小儿和成年患者的作用，由于其有可能限制PET扫描的诊断质量并干扰治疗反应评估，因此认识到这一点很重要。目的与在多达三分之一的儿科PET扫描中发现的众所周知的具有代谢活性的棕色脂肪不同，白色脂肪通常不具有代谢活性。我们力求确定正在接受PET成像的儿科患者皮下白色脂肪组织中FDG分布改变的发生率，并评估与皮质类固醇使用的关联。材料和方法我们回顾了在常规临床实践中确定的诱导后FDG PET / CT上出现白色脂肪组织生物分布改变的四个孩子的病历和影像学检查。这四个人都在接受皮质类固醇化疗。然后，我们回顾性地回顾了为期2年的肿瘤学FDG PET / CT扫描（689例患者进行了1,361例扫描），以通过定性视觉评估确定白色脂肪摄取的发生率。在发现生物分布发生变化的儿童中，我们测量了皮下白色脂肪，颊区域，体壁或臀软组织区域，肝脏和血池区域的最大标准摄取值（SUVmax）和平均标准摄取值（SUVmean）。我们审查了所有医疗记录，包括药物清单。我们总结了13例儿科患者的相关临床和影像学表现，包括4例索引患者。结果我们确定了白色脂肪中FDG摄取的发生率是罕见的，在进行的1,361例（0.6％）PET扫描中有9例用于儿科癌症评估。在皮下脂肪组织中，尤其是在颊区域，体壁和臀区域中，FDG的摄取增加，同时放射性示踪剂从血池和肝脏移开。周围白色脂肪摄取的增加程度从明显到轻度不等，其生物分布与棕色脂肪组织不同。具有这种生物分布改变的儿童均接受皮质类固醇激素作为其癌症诱导治疗的一部分，而这些发现仅在诱导后PET / CT上才能确定。后续的PET / CT记录了停用皮质类固醇激素后这种作用的缓解。结论我们的发现支持了目前的认识，即白色脂肪组织中FDG的特征性摄取是由糖皮质激素作用介导的。尽管这种改变的生物分布很少见（不到PET扫描的1％），但它可能会损害扫描的诊断质量，影响图像的解释，当出现时应予以识别。具有这种生物分布改变的儿童均接受皮质类固醇激素作为其癌症诱导治疗的一部分，而这些发现仅在诱导后PET / CT上才能确定。后续的PET / CT记录了皮质类固醇治疗停止后这种作用的缓解。结论我们的发现支持了目前的认识，即白色脂肪组织中FDG的特征性摄取是由糖皮质激素作用介导的。尽管这种改变的生物分布很少见（不到PET扫描的1％），但它可能会损害扫描的诊断质量，影响图像的解释，因此在出现时应予以识别。具有这种生物分布改变的儿童均接受皮质类固醇激素作为其癌症诱导治疗的一部分，而这些发现仅在诱导后PET / CT上才能确定。后续的PET / CT记录了停用皮质类固醇激素后这种作用的缓解。结论我们的发现支持了目前的认识，即白色脂肪组织中FDG的特征性摄取是由糖皮质激素作用介导的。尽管这种改变的生物分布很少见（不到PET扫描的1％），但它可能会损害扫描的诊断质量，影响图像的解释，因此在出现时应予以识别。结论我们的发现支持了目前的认识，即白色脂肪组织中FDG的特征性摄取是由糖皮质激素作用介导的。尽管这种改变的生物分布很少见（不到PET扫描的1％），但它可能会损害扫描的诊断质量，影响图像的解释，因此在出现时应予以识别。结论我们的发现支持了目前的认识，即白色脂肪组织中FDG的特征性摄取是由糖皮质激素作用介导的。尽管这种改变的生物分布很少见（不到PET扫描的1％），但它可能会损害扫描的诊断质量，影响图像的解释，因此在出现时应予以识别。