Purpose The aim of this case series is to illustrate the ¹⁸F-FDG PET/CT findings of patients with acute respiratory disease caused by COVID-19 in Wuhan, Hubei province of China. Methods We describe the ¹⁸F-FDG PET/CT results from four patients who were admitted to the hospital with respiratory symptoms and fever between January 13 and January 20, 2020, when the COVID-19 outbreak was still unrecognized and the virus infectivity was unknown. A retrospective review of the patients’ medical history, clinical and laboratory data, as well as imaging findings strongly suggested a diagnosis of COVID-19. Results All patients had peripheral ground-glass opacities and/or lung consolidations in more than two pulmonary lobes. Lung lesions were characterized by a high ¹⁸F-FDG uptake and there was evidence of lymph node involvement. Conversely, disseminated disease was absent, a finding suggesting that COVID-19 has pulmonary tropism. Conclusions Although ¹⁸F-FDG PET/CT cannot be routinely used in an emergency setting and is generally not recommended for infectious diseases, our pilot data shed light on the potential clinical utility of this imaging technique in the differential diagnosis of complex cases.

We sought to evaluate the performance of ⁶⁸Ga-DOTA-FAPI-04 (⁶⁸Ga-FAPI) PET/MR for the diagnosis of primary tumor and metastatic lesions in patients with gastric carcinomas and to compare the results with those of ¹⁸F-FDG PET/CT. Methods: Twenty patients with histologically proven gastric carcinomas were recruited, and each patient underwent both ¹⁸F-FDG PET/CT and ⁶⁸Ga-FAPI PET/MR. A visual scoring system was established to compare the detectability of primary tumors and metastases in different organs/regions (the peritoneum, abdominal lymph nodes, supradiaphragmatic lymph nodes, liver, ovary, bone, and other tissues). The original maximum standardized uptake value (SUV_max) and normalized SUV_max (calculated by dividing a lesion’s original SUV_max with the mean SUV of the descending aorta) of selected lesions on both ¹⁸F-FDG PET/CT and ⁶⁸Ga-FAPI PET/MR were measured. Original/normalized SUV_max-FAPI and SUV_max-FDG were compared for patient-based (including a single lesion with the highest activity uptake in each organ/region) and lesion-based (including all lesions [≤ 5] or the 5 lesions with highest activity [> 5]) analyses, respectively. Results: The 20 recruited patients (median age: 56.0 y; range: 29–70 y) included 9 men and 11 women, 14 patients for initial staging and 6 for recurrence detection. ⁶⁸Ga-FAPI PET was superior to ¹⁸F-FDG PET for primary tumor detection (100.00% [14/14] vs 71.43% [10/14], P = 0.034), and the former had higher tracer uptake levels (P < 0.05). ⁶⁸Ga-FAPI PET was superior to ¹⁸F-FDG PET in both patient-based and lesion-based evaluation except for the metastatic lesions in supradiaphragmatic lymph nodes and ovaries. Additionally, multiple sequences of MR images were beneficial for the interpretation of hepatic metastases in 3 patients, uterine and rectal metastases in 1 patient, ovarian lesions in 7 patients, and osseous metastases in 2 patients. Conclusion:⁶⁸Ga-FAPI PET/MR outperformed ¹⁸F-FDG PET/CT in visualizing the primary and most metastatic lesions of gastric cancer, and might be a promising method with the potential of replacing ¹⁸F-FDG PET/CT.

Upconversion nanoparticles (UCNPs) have been widely employed for tumor imaging using magnetic resonance imaging (MRI) and upconversion luminescence (UCL) imaging. The short blood clearance time and immunogenicity of UCNPs have limited their further application in vivo. We have designed UCNPs camouflaged with an exterior red blood cell (RBC) membrane coating (RBC-UCNPs) to solve these problems. Moreover, because of some intrinsic disadvantages of MRI and UCL imaging, we investigated the use of pretargeted RBC-UCNPs for positron-emission tomography (PET) imaging to obtain more comprehensive information. Our data showed that RBC-UCNPs retained the immunity feature from the source cells and the superior optical and chemical features from the pristine UCNP cores. The tumor-targeting ability of RBC-UCNPs was enhanced by binding 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[folate(polyethylene glycol)-2000] (DSPE-PEG-FA) molecules onto the cell membranes. PET imaging with short half-life radionuclides to visualize the RBC-UCNPs was successfully realized by a combination of pre-targeting and in vivo click chemistry. Blood chemistry, hematology, and histologic analysis suggested good in vivo biocompatibility of the RBC-UCNPs. Our method provides a new potential biomedical application of biomimetic nanoparticles.