68 Ga-conjugated fibroblast activation protein inhibitor ( 68 Ga-FAPI) has become an attractive agent for positron emission tomography (PET). This study aimed to compare 68 Ga-FAPI-46 PET/computed tomography (CT) with 18 F-fluorodeoxy-D-glucose ( 18 F-FDG) PET/CT for detecting primary cancer and metastatic lesions in patients with head and neck squamous cell carcinoma (HNSCC).Methods: Twelve patients and twenty-eight patients with HNSCC underwent 68 Ga-FAPI-46 and 18 F-FDG PET/CT for initial staging and recurrence detection, respectively. Concordance and diagnostic accuracy of both tracers were analyzed. Semiquantitative parameters, including the maximum and mean of standardized uptake value (SUVmax and SUVmean) and tumor-tobackground ratio (T/B) were compared. FAP expression tumor volume (FTV) and total lesion FAP expression (TLF) of 68 Ga-FAPI-46 were compared with metabolic tumor volume (MTV) and total lesion glycolysis (TLG) of 18 F-FDG, respectively. Differences between semiquantitative parameters were analyzed using paired t-tests.Results: 68 Ga-FAPI -46 PET/CT was 83.3% and 96.4% concordant with 18 F-FDG PET/CT for initial staging and recurrence detection, respectively. Eighteen lesions had histopathological validation and both tracers displayed 100% sensitivity, 50% specificity, and 94.4% accuracy for lesion-based analysis. FTV was greater than MTV (P < 0.05), but no significant differences were observed for the other parameters. Conclusion:68 Ga-FAPI-46 PET/CT showed good concordance and comparable diagnostic performance compared with 18 F-FDG PET/CT for initial staging and recurrence detection in patients with HNSCC.

Purpose To compare quantitative parameters and tumour detection rates of [ 68 Ga]Ga-FAPI PET/CT with those of dedicated liver PET/MRI and 18 F-FDG PET in patients with liver malignancies. Procedures Twenty-seven patients (29 imaging studies) with diagnosed or suspected liver malignancies who underwent [ 68 Ga]Ga-FAPI-46 PET/CT, liver PET/MRI, and [ 18 F]FDG PET/CT between September 2020 and June 2021 were retrospectively analysed. MRI findings were used as the reference standard for diagnosis. Results The 27 patients had a median age of 68 years (interquartile range: 60–74 years; 21 men). Primary intrahepatic tumours were reported in 13 patients (15 imaging studies) with cholangiocarcinoma (CCA) and in 14 patients with hepatocellular carcinoma (HCC). All intrahepatic lesions detectable on MRI were also detected on [ 68 Ga]Ga-FAPI-46 PET/CT giving a sensitivity of 100% (19/19), whereas the sensitivity of [ 18 F]FDG PET/CT was 58% (11/19). All intrahepatic lesions were detected on [ 68 Ga]Ga-FAPI-46 PET/CT, on which they showed higher activity (median SUVmax: 15.61 vs. 5.17; P < .001) and higher target-to-background ratio (TBR; median, 15.90 vs. 1.69, P < .001) than on [ 18 F]FDG, especially in patients with CCA (median TBR, 21.08 vs. 1.47, respectively; P < .001). The uptake positivity rate in regional node metastasis was 100% (12/12) on [ 68 Ga]Ga-FAPI-46 PET/CT compared with 58% (7/12) on [ 18 F]FDG PET/CT. All patients with distant metastasis (100%, 14/14) were detected on both [ 18 F]FDG and [ 68 Ga]Ga-FAPI-46 PET/CT imaging, although more distant metastatic lesions were detected on [ 68 Ga]Ga-FAPI-46 PET/CT than on [ 18 F]FDG (96% (42/44) vs. 89% (39/44), respectively). Conclusion [ 68 Ga]Ga-FAPI PET/CT with dedicated liver PET/MRI shows potential for superior detection of hepatic malignancy compared with [ 18 F]FDG PET/CT or MRI alone. Supplementary Information The online version contains supplementary material available at 10.1007/s11307-022-01732-2.

Purpose The study aimed to investigate imaging abnormalities associated with post-acute COVID-19 using F-18 FDG PET/CT and PET/ rsfMRI brain. Methods We retrospectively recruited 13 patients with post-acute COVID-19. The post-acute COVID-19 symptoms and neuropsychiatric tests were performed before F-18 FDG PET/CT whole body with PET/rsfMRI brain. Qualitative and semiquantitative analyses were also conducted in both whole body and brain images. Results Among the 13 patients, 8 (61.5%) had myositis, followed by 8 (61.5%) with vasculitis (mainly in the thoracic aorta), and 7 (53.8%) with lung abnormalities.. Interestingly, one patient with a very high serum RBD IgG antibody demonstrated diffuse myositis throughout the body which potentially associated with immune-mediated myositis. One patient experienced psoriasis exacerbation with autoimmune-mediated after COVID-19. Most patients had multiple areas of abnormal brain connectivity involving the frontal and parieto-temporo-occipital lobes, as well as the thalamus. Conclusion The whole body F-18 FDG PET can be a potential tool to assess inflammatory process and support the hyperinflammatory etiology, mainly for lesions in skeletal muscle, vascular wall, and lung, as well as, multiple brain abnormalities in post-acute COVID-19. Nonetheless, further studies are recommended to confirm the results.

Purpose This study aimed to investigate functional abnormalities in the brain of patients with neurological adverse effects following COVID-19 (coronavirus disease 2019) vaccination using 18 F-FDG PET/MRI and 15 O-water PET. Methods Eight patients (1 man and 7 women, aged 26–47 years [median age, 36.5 years]) who experienced neurological symptoms after the first COVID-19 vaccination underwent CT, MRI, 18 F-FDG PET/MRI, and 15 O-water PET of the brain. After 7 days, each patient underwent a follow-up 18 F-FDG PET/MRI and 15 O-water PET of the brain. Imaging data were analyzed using visual and semiquantitative analyses, which included a cluster subtraction workflow ( P = 0.05). Results There was no evidence of vascular abnormalities, acute infarction, or hemorrhage on the CT or MRI scans. On the 15 O-water PET images, 1 patient had mildly significant decreases in perfusion in the bilateral thalamus and bilateral cerebellum, and another patient showed a diffuse increase in perfusion in the cerebral white matter. The visual and semiquantitative analyses showed hypometabolism in the bilateral parietal lobes in all 8 patients on both the first and follow-up 18 F-FDG PET/MRI scans. Metabolic changes in the bilateral cuneus were also observed during the first visit; all patients exhibited neurological symptoms. Moreover, 6 patients showed hypometabolism, and 2 patients showed hypermetabolism. Conclusion All regions of metabolic abnormality were part of the fear network model that has been implicated in anxiety. Our study findings support the concepts of and provide evidence for the immunization stress-related response and the biopsychosocial model.

Background: The study aimed to evaluate the appropriate uptake-timing in cognitively normal individuals, mild cognitive impairment (MCI), and Alzheimer’s disease (AD) patients, using 18F-PI 2620 dynamic PET acquisition. Methods: Thirty-four MCI patients, 6 AD patients, and 24 cognitively normal individuals were enrolled in this study. A dynamic 18F-PI 2620 PET study was conducted at 30-75 minutes post-injection in these groups. Co-registration was applied between the dynamic acquisition PET and T1-weighted MRI to delineate various cortical regions. The standardized uptake value ratio (SUVR) was used for quantitative analysis. P-mod software with the Automated Anatomical Labeling (AAL)-merged atlas was employed to generate automatic volumes of interest for 11 brain regions. Results: The curves in most brain regions presented an average SUVR stability at 30-40 minutes post-injection in each group. The appropriate uptake-timing interval of 18F-PI 2620 was 30-75 minutes post injection for AD group and 30-40 minutes post injection for both cognitively normal individuals and MCI groups. Conclusion: Short uptake time around 30-40 minutes post-injection would be more comfortable and convenient for all patients, especially in those with dementia who were unable to stay motionless for long periods of scanning time in the scanner.