Division of Nuclear Medicine, Department of Radiology, C. S. Mott Children's Hospital, University of Michigan Health System, B1G505 University Hospital SPC 5028, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109-5028, USA.
Division of Hematology, Oncology and Bone Marrow Transplant, Department of Pediatrics, C. S. Mott Children's Hospital, University of Michigan Health System, Ann Arbor, MI, USA.
Pediatr Radiol. 2020 Apr;50(4):524-533. doi: 10.1007/s00247-019-04574-3. Epub 2019 Nov 27.
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.
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.
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 (SUV) and mean standard uptake value (SUV) 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.
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.
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.
在接受淋巴瘤诱导后正电子发射断层扫描（PET）成像的儿科患者中，有时会遇到 [F-18]2-氟-2-脱氧葡萄糖（FDG）的生物分布改变。可以看到白色脂肪组织中 FDG 摄取增加的特征性模式，特别是在颊部、体壁和臀区，示踪剂从血池和肝脏转移。这种生物分布改变归因于儿科和成人患者中皮质类固醇的作用，这一点很重要，因为它可能会限制 PET 扫描的诊断质量，并干扰治疗反应评估。
与多达三分之一儿科 PET 扫描中可见的代谢活跃的棕色脂肪不同，白色脂肪通常是非代谢活跃的。我们旨在确定在接受 PET 成像的儿科患者中，皮下白色脂肪组织中 FDG 分布改变的发生率，并评估其与皮质类固醇使用的关系。
我们在常规临床实践中发现了 4 名儿童的白色脂肪组织中 FDG 生物分布改变，回顾了他们的病历和影像学资料。这 4 名儿童均接受皮质类固醇治疗作为其化疗的一部分。然后，我们回顾性地分析了 2 年内的肿瘤学 FDG PET/CT 扫描（689 名患者的 1361 次扫描），通过定性视觉评估确定白色脂肪的摄取情况。在发现生物分布改变的儿童中，我们测量了皮下白色脂肪、颊部、体壁或臀区软组织、肝脏和血池的最大标准摄取值（SUV）和平均标准摄取值（SUV）。我们回顾了所有病历，包括药物清单。我们总结了 13 名儿科患者（包括 4 名指数患者）的相关临床和影像学发现。
我们确定 FDG 在白色脂肪中的摄取罕见，在 1361 次儿科癌症评估的 PET 扫描中仅发现 9 次（0.6%）。FDG 在皮下脂肪中摄取增加，特别是在颊部、体壁和臀区，示踪剂从血池和肝脏转移。外周白色脂肪摄取增加的程度从明显到轻度不等，其生物分布与棕色脂肪不同。接受这种生物分布改变的儿童均接受皮质类固醇诱导治疗癌症，并且仅在诱导后 PET/CT 上发现这些发现。皮质类固醇治疗停止后，随访 PET/CT 记录到这种作用的消退。
我们的研究结果支持目前的认识，即 FDG 在白色脂肪中的特征性摄取是由皮质类固醇作用介导的。尽管这种生物分布改变很少见（<1%的 PET 扫描），但它可能会影响扫描的诊断质量，影响图像解释，并且在存在时应予以识别。
