The incidence and duration of COVID-19 vaccine-related reactive lymphadenopathy on 18F-FDG PET-CT.

OBJECTIVES: Reactive axillary lymph nodes (ALN) may occur post-COVID-19 vaccination. This may be confused with malignant nodal metastases on oncological imaging. We aimed to determine the reactive ALN incidence and duration on 18F-fluorodeoxyglucose positron emission tomography - computed tomography (18F-FDG PET-CT), and its relationship with gender, age and vaccine type. METHODS: A retrospective study was performed. Two-hundred and four eligible patients had 18F-FDG PET-CT between 01 January 2021 and 31 March 2021, post-vaccination with Pfizer-BioNTech or Oxford-AstraZeneca vaccine. Image analysis was performed on dedicated workstations. SPSS was used for statistical analysis. RESULTS: Thirty-six per cent of patients had reactive ALN until 10 weeks post-vaccination; reducing in frequency and intensity with time. Women were more likely to have reactive ALN compared with men. The frequency and intensity were higher in patients aged <65 years compared with those aged ≥65 years. However, no difference was found between both vaccine types in our study cohort. CONCLUSIONS: Physicians' awareness of COVID-19 vaccine-related reactive ALN on 18F-FDG PET-CT is important to avoid inappropriate upstaging of cancers.

Identification of brown adipose tissue using MR imaging in a human adult with histological and immunohistochemical confirmation.

OBJECTIVE: Manipulation of human brown adipose tissue (BAT) represents a novel therapeutic option for diabesity. The aim of our study was to develop and test a novel magnetic resonance (MR) imaging-based method to identify human BAT, delineate it from white adipose tissue, and validate it through immunohistochemistry. DESIGN: A 25-year old Caucasian female with hyperparathyroidism-jaw tumor syndrome underwent parathyroidectomy. An (18)fluoro-2-deoxyglucose positron emission tomography (PET)-computed tomography (CT) scan performed after surgery ruled out malignancy but showed avid uptake within the mediastinum, neck, supraclavicular fossae, and axillae, consistent with BAT. Immunohistochemical staining using uncoupling protein-1 antibody was performed on one fat sample obtained from the suprasternal area during parathyroidectomy. Subsequently, serial MR scans were performed. Retrospectively, regions of interest (ROIs) were identified on MR corresponding to areas of high uptake on PET-CT. Prospectively, ROIs were identified on MR based on signal intensity and appearance and compared with PET-CT. RESULTS: Of 111 retrospectively identified ROIs from PET-CT, 93 (83.8%) showed corresponding low MR signal: 25 of 25 mediastinum (100%), 29 of 31 neck (93.5%), 31 of 41 supraclavicular (75.6%), and 8 of 14 axillae (57%). Prospectively, 47 of 54 ROIs identified on MR (87%) showed a corresponding increased uptake on PET-CT. Serendipitously, the sample obtained at surgery corresponded with high uptake and low signal on subsequent PET and MR, respectively, and immunohistochemistry confirmed BAT. CONCLUSION: We provide the first report for the reliable use of MR to identify BAT in a living human adult, with histological/immunohistochemical confirmation. Our data demonstrate proof of concept to support the development of MR as a safe, reproducible imaging modality for human BAT.

Orbital carcinoid metastasis: diverse presentations and value of indium-octreotide imaging.

PURPOSE: To report two cases of orbital carcinoid metastasis (OCM) with diverse presentations and the role of Indium-Octreotide scan in management of these patients. METHODS: Clinical, histological and radiological findings and management of the two patients are described. Results are presented. CONCLUSIONS: We wish to highlight the diversity of presentations in orbital carcinoid. One patient presented with headache, while the other presented with recurrent transient ptosis. To the best of our knowledge, there have been no previous reports of OCM presenting as transient ptosis. The value of Indium-Octreotide scan in detecting the true extent of systemic disease and reducing the need for biopsy in carcinoid tumour is discussed.