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Optimal scan time of F-fluorocholine (FCH) PET/CT for localization of hyperfunctioning parathyroid glands is poorly documented. We report a small series of 9 histologically proven hyperfunctioning parathyroid gland with heterogeneous temporal uptake profile. Thirty-minute dynamic acquisition starting just after F-fluorocholine administration and delayed acquisition were recorded. Three different uptake patterns are seen (early washout, stable uptake, late increase) indicating the importance of an early (5-10 minutes) acquisition. A late acquisition (60 minutes) could be useful when the early acquisition is negative. No correlations were noted between uptake profile and histological or genetic results.

Rationale: We aimed to predict the presence of vaccine-induced hypermetabolic lymph nodes (v-HLN) on 18 F-FDG PET/CT after Coronavirus disease 2019 (COVID-19) vaccination and determine their association with lymphocyte counts. Methods: In this retrospective single-center study, we included consecutive patients who underwent 18 F-FDG PET/CT imaging after mRNA-or viral vector-based COVID-19 vaccination between early March and late April 2021. Demographic, clinical parameters and absolute lymphocyte count (ALC) were collected and their association with the presence of v-HLN in the draining territory was studied by logistic regression.Results: Two hundred and sixty patients were eligible, including 209 (80%) women and 145 (56%) with breast cancer. The median age was 50 years (range, 23-96). Two hundred thirty-three patients (90%) received the mRNA vaccine. Ninety (35%) patients had v-HLN with a median SUVmax of 3.7 [range, 2.0-26.3] and 74 (44%) displayed lymphopenia with a median ALC of 1.4 G/L [range, 0.3-18.3]. Age ≤ 50 years (odds ratio [OR] 2.2, 95%CI 1.0-4.5), the absence of lymphopenia (OR 2.2, 95%CI 1.1-4.3) and the delay from the last vaccine injection to the date of 18 F-FDG PET/CT, if < 30 days (OR 2.6, 95%CI 1.3-5.6), were independent factors for v-HLN in multivariate analysis. In breast cancer patients, the absence of lymphopenia was the only independent factor significantly associated with v-HLN (OR 2.9, 95%CI 1.2-7.4).Conclusions: Patients with normal values of ALC after COVID-19 vaccine were more likely to have v-HLN on 18 F-FDG PET/CT, which might both be associated to a stronger immune response to vaccination. KEYWORDS 18 F-FDG PET/CT; COVID-19 vaccination; absolute lymphocyte count; hypermetabolic lymph nodes; immune response. KEY-POINTSQUESTION: Could we use lymphocyte count lymphocyte for predicting the presence of vaccineinduced hypermetabolic lymph node(s) in the drainage territory on 18 F-FDG PET/CT following COVID-19 vaccination?PERTINENT FINDINGS: This retrospective and monocentric study included 260 vaccinated patients who underwent 18 F-FDG PET/CT following mRNA based-or viral vector based-COVID-19 vaccination. Patients' absolute lymphocyte count (>lower limit of normal), along with patients' age (≤ 50 years) and the timing of last injection dose (< 30 days), significantly correlated with vaccine-induced hypermetabolic lymph node(s).IMPLICATIONS FOR PATIENT CARE: Patients displaying normal count of lymphocytes after COVID-19 vaccination are more likely to present vaccine-induced hypermetabolic lymph node(s) on 18 F-FDG PET/CT and could subsequently have higher seropositivity likelihood and antibody titers.

Hyperparathyroidism is a common endocrine disorder. The precise localization of causal parathyroid gland is crucial to guide surgical treatment. Several studies report the added value of 18F-fluorocholine (FCH) positron emission tomography-computed tomography (PET/CT) as second line imaging but rely on suboptimal first-line imaging using 99mTc-sestaMIBI dual phase scintigraphy. The aim of this study is to evaluate the percentage of successful parathyroid localization with FCH PET/CT after failure of a more sensitive first-line detection protocol associating neck ultrasonography and 99mTc-Pertechnetate/99mTc-sestaMIBI dual tracer subtraction scintigraphy. We included retrospectively 47 patients who underwent a FCH PET/CT as second line imaging for biologically proven primary hyperparathyroidism from November 2016 to October 2018 in Godinot Institute (Reims, France). 99mTc-Pertechnetate/99mTc-sestaMIBI dual tracer subtraction scintigraphy and neck ultrasonography were used as first-line imaging and failed to localize the causal parathyroid lesion in all cases. FCH PET/CT demonstrated at least 1 parathyroid target lesion in 29 patients (62%). 21/29 patients underwent surgery. Target lesions corresponded histologically to hyperfunctioning parathyroid glands for all 21 patients and surgery was followed by hyperparathyroidism biological resolution. Calcium serum levels were associated to FCH PET/CT positivity (P = .002) and a trend toward significance was seen for Parathyroid hormone (PTH) levels (P = .09). FCH PET/CT is a promising tool in second-line parathyroid imaging. Large prospective studies and cost-effectiveness analyses are needed to precise its role.

SUMMARY Osteoarticular amyloidosis occurred in a patient receiving long term haemodialysis. Histological examination showed that the amyloid deposit was surrounded by inflammatory cells and macrophages filled with haemosiderin. Electron microscopy showed that the amyloid fibrils were in close contact with cytoplasmic expansions, or located in intracytoplasmic pockets of the infiltrating cells. Immunohistological and immunoultrastructural observations confirmed that f2-microglobulin was a major constituent of amyloidosis associated with dialysis. Amyloid P component was also detected within the amyloid deposits.These findings suggest that amyloid P component, iron overload, or macrophage derived factors could have a role in the polymerisation of #2-microglobulin into amyloid deposit.