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Objectives: The aim of this study was to determine the performance of radionuclide-labeled fibroblast activation protein inhibitors (Al18F-NOTA-FAPI-04) PET/CT in patients with autoimmune rheumatic diseases (ARDs) and compare it with fluorine-18 (18F) labeled fluorodeoxyglucose (FDG) imaging. Methods: Fifty-eight participants with ARDs were prospectively enrolled from April 2022 to February 2024 and underwent dual-tracer PET/CT imaging. For both 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT, imaging findings were interpreted and compared. The clinical significance was compared between18F-FDG PET/CT and Al18F-NOTA-FAPI-04 PET/CT imaging. Results: 18F-FDG imaging was positive in 53 out of 58 cases (91.4%) while Al18F-NOTA-FAPI-04 imaging was positive in 55 out of 58 cases (94.8%). Overall positive rate of Al18F-NOTA-FAPI-04 imaging was as high as 18F-FDG imaging (P = 0.625). 18F-FDG imaging detected more lesions in lymph node, spleen, and bone marrow. Al18F-NOTA-FAPI-04 imaging detected more lesions in the lung, muscle, and tendon/ligament. There was no statistical difference of composing ratio of grades of clinical significance between two imaging modalities (χ2 = 2.875, P = 0.238). The superior rate of Al18F-NOTA-FAPI-04 PET/CT imaging was higher than 18F-FDG imaging (P = 0.020). In subgroup of adult-onset Still's disease, 18F-FDG imaging showed better performance than Al18F-NOTA-FAPI-04 imaging. In most of the other subgroup of ARDs, Al18F-NOTA-FAPI-04 PET/CT imaging overperformed 18F-FDG imaging. Conclusion: Both 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT imaging have excellent sensitivity in ARDs. The detection capabilities of two tracers varied according to the involving organs of ARDs. In most of ARDs except adult-onset Still's disease, Al18F-NOTA-FAPI-04 PET/CT imaging overperformed 18F-FDG imaging. Key Points • 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT imaging have excellent sensitivity in diagnosing of ARDs. • 18F-FDG PET/CT imaging detected more lesions in lymph node, spleen, and bone marrow. • 18F-NOTA-FAPI-04 PET/CT imaging detected more lesions in the lung, muscle, and tendon/ligament. • 18F-NOTA-FAPI-04 PET/CT imaging overperformed18F-FDG in most subgroups of ARDs. [ABSTRACT FROM AUTHOR]

Objective: To analyze 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) image features in different types of systemic vasculitis and explore its classification and diagnostic significance for systemic vasculitis. Methods: Clinical and 18F-FDG PET/CT imaging data of 71 consecutive patients (34 males, 37 females, mean age 53.4 ± 20.5 years) who were examined at Peking University People's Hospital and diagnosed with active systemic vasculitis were analyzed retrospectively, and 18F-FDG PET/CT imaging features of different types of systemic vasculitis were analyzed in patients with positive 18F-FDG PET/CT findings. Results: The proportions of large-, medium-, small-, and variable-vessel vasculitis were 36.6%, 15.5%, 29.6%, and 18.3%, respectively, and 93.0% of patients had positive findings on PET/CT, of which 63.6% had vascular involvement and 53.0% had extravascular involvement. Different types of vasculitis had different lesion sites, distribution patterns, and morphological changes. Large-vessel vasculitis mainly affected the aorta and its branches to the head and neck. Takayasu arteritis showed segmental involvement of the vascular and morphological changes of the vessel wall. Giant cell arteritis manifested as diffuse vascular involvement, which usually involved the temporal artery and the abdominal aorta and its branches. Medium-vessel vasculitis polyarteritis nodosa manifested as diffuse vascular involvement of both lower extremities. Small-vessel vasculitis anti-neutrophil cytoplasmic antibody-associated vasculitis manifested as granulomatous inflammation of extravascular regions. Variable-vessel vasculitis Behcet's disease involved both blood vessels and extravascular regions. Conclusion: Different types of systemic vasculitis show characteristic manifestations in 18F-FDG PET/CT images, which may be useful for the diagnosis and classification of systemic vasculitis. Key points: • Determining an early diagnosis of systemic vasculitis may be challenging. • Different types of systemic vasculitis show characteristic manifestations in 18F-FDG PET/CT images. • 18F-FDG PET/CT may be useful for the diagnosis and classification of systemic vasculitis. [ABSTRACT FROM AUTHOR]

Objective: To explore the significance of Fluorine-18 labeled fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in diagnosing connective tissue diseases (CTDs) in fever of unknown origin (FUO) or inflammation of unknown origin (IUO) patients. Methods: Clinical and image data of 242 consecutive FUO/IUO patients who underwent PET/CT examination and eventually diagnosed CTDs were retrospectively analyzed, including distribution of diseases, clinical characteristics, and PET/CT imaging findings. The role of FDG PET/CT in differential diagnosis of CTDs was evaluated through clinical questionnaire survey. Results: Patients diagnosed as CTDs accounted for 48.1% of FUO/IUO patients. Among them, adult-onset Still's disease was most frequently diagnosed. Other common diseases included systemic vasculitis, undifferentiated connective tissue disease, rheumatoid arthritis, idiopathic inflammatory myopathy, systemic lupus erythematosus, and polymyalgia rheumatica. On FDG PET/CT examination, 97.9% of the patients had positive findings. Inflammatory lesions were detected in 66.5% and non-specific abnormal uptakes were found in 31.4%. Detected lesions distributed consistently with corresponding susceptible organs and tissues in various diseases. Clinical questionnaire results shown that FDG PET/CT excluded malignant tumors, focal infections, or other typical CTDs in 45.5% of the patients; indicated important diagnostic clues or appropriate biopsy sites in 20.6% of patients; and directly suggested the diagnosis of a CTD in 33.1% of patients. Conclusion: FDG PET/CT could reveal inflammatory lesions in organs and tissues that reflect the clinical characteristics in different CTDs, thus providing an objective evidence for differential diagnosis, classification, and treatment decision of these diseases. Key Points • FDG PET/CT is a useful tool for differential diagnosing connective tissue diseases among patients with fever of unknown origin/inflammatory of unknown origin. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the multiple values of F-FDG PET/CT in detecting malignant tumors, evaluating myopathy, and determining interstitial lung disease in patients with idiopathic inflammatory myopathy (IIM). We retrospectively analyzed the data of 38 patients who were examined by F-FDG PET/CT and eventually diagnosed as IIM. We also collected the data of another 22 cases with negative PET/CT as the control. Pulmonary HRCT images were acquired simultaneously with regular F-FDG PET/CT imaging for each patient. Image analysis included the presence of malignant lesions, muscular FDG uptake, and interstitial lung disease and its imaging features. IIM was classified into polymyositis (PM), classic dermatomyositis (CDM), and clinical amyopathic dermatomyositis (CADM). All suspected malignant lesions were confirmed by histopathological examination. Interstitial lung disease was diagnosed by HRCT. Rapidly progressive interstitial lung disease (RP-ILD) was determined according to clinical follow-ups. The significance of F-FDG PET/CT in the detection of malignancy, observation of activity of myopathy, and determination of interstitial lung disease in IIM patients was explored based on the final clinical diagnosis. In the 38 patients with IIM, 3 cases were classified as PM, 18 as CDM, and 17 as CADM. PET/CT correctly detected 7 cases (18.4%) of malignant tumors, and all of which were found in CDM and PM patients. The muscular FDG uptake in IIM patients was higher than the control population, and it was higher in patients with myopathy (including PM and CDM) than in patients with CADM. The muscular FDG uptake in IIM patients was correlated with elevated serum creatine kinase level ( r = 0.332, P = 0.042) and impaired muscle strength ( r = −0.605, P < 0.001). Interstitial lung disease was detected by HRCT in 30 patients (78.9%), and 7 of them were eventually confirmed as RP-ILD, according to the clinical outcome. The FDG uptake in lung lesions of RP-ILD patients was higher than those with chronic interstitial lung diseases, even though no significant difference was found between the CT features of RP-ILD and chronic interstitial lung disease. When SUV ≥ 2.4 was employed as the threshold for RP-ILD prediction, the diagnostic efficiency was yield with a sensitivity of 100.0% (7/7), specificity of 87.0% (20/23), and accuracy of 90.0% (27/30), respectively. For IIM patients, F-FDG PET/CT has multiple values in identifying malignancies, observing the status of inflammatory myopathy, detecting interstitial lung disease, and predicting the occurrence of RP-ILD. Therefore, it is recommended to use PET/CT in the clinical course of diagnosis and management of IIM. [ABSTRACT FROM AUTHOR]