Yuan Li

Objectives: Respiratory motion degrades the quantitative accuracy and test–retest (TRT) reliability of fluorine-18 fluorodeoxyglucose ([¹⁸F] FDG) positron emission tomography (PET)/computed tomography (CT) in lung cancer. This study investigated whether a deep-learning-based respiratory motion correction (RMC) method improves the TRT reliability and image quality of [¹⁸F] FDG PET tumor quantification compared with non-motion-corrected (NMC) reconstructions. Methods: Thirty-one patients with primary lung cancer underwent three PET acquisitions: whole body free breathing (Scan1), thoracic free breathing (Scan2), and thoracic controlled breathing (ScanCB). Each dataset was reconstructed with and without RMC. Visual assessments of liver motion artifacts, lesion clarity, and PET-CT co-registration were scored. Lung tumors were segmented to derive standardized uptake value max (SUVmax), SUVmean, metabolic tumor volume (MTV), PET-derived lesion length (PLL), and total lesion glycolysis (TLG). Visual image scores and TRT reliability of tumor quantification were compared using Kruskal–Wallis one-way analysis of variance and intraclass correlation coefficients (ICCs). Results: RMC reconstructions achieved higher visual scores of lesion clarity and PET-CT co-registration across all lung lobes and significantly reduced liver motion artifacts compared with NMC reconstructions. Differences in SUVmax, SUVmean, PLL, MTV, and TLG between Scan2 and ScanCB were significantly smaller with RMC than with NMC. ICCs for SUVmax, SUVmean, MTV, and TLG were higher between scans with RMC than NMC reconstructions, indicating improved TRT reliability. Conclusions: The deep-learning-based RMC method improved the image quality and TRT reproducibility of [¹⁸F] FDG PET/CT quantification in lung cancer, supporting its potential for routine adoption in therapy-response assessments.

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.

Objective The aim of this study was to compare the recent Positron emission tomography (PET) Response Criteria in Solid Tumors (PERCIST) and Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria for evaluating the response of osteosarcoma to neoadjuvant chemotherapy of the extremities. Methods We retrospectively reviewed patients with osteosarcoma of the extremities who received neoadjuvant chemotherapy and then surgical resection at Peking University People’s Hospital. Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) and magnetic resonance imaging (MRI) were performed prior to chemotherapy and before surgical resection. Therapeutic response was assessed separately by the PERCIST and RECIST 1.1 criteria. The association between the data acquired by the PERCIST and RECIST 1.1 criteria was then analyzed by Wilcoxon’s signed-rank test. The association between the PERCIST criteria and the pathological necrosis rate was analyzed by Fisher’s exact test. Finally, the impact of a range of clinicopathological factors on overall survival (OS) and event-free survival (EFS) was analyzed by Cox proportional hazards regression. Results We recruited 68 patients with a median follow-up of 74 months (range 45–102 months). The evaluations resulting from the RECIST 1.1 and PERCIST criteria were significantly different (p = 0.000). Only two responders were identified according to the RECIST 1.1 criteria. However, 34 responders were identified by the PERCIST criteria. Data arising from the PERCIST criteria were in accordance with the pathological necrosis rate. Survival analysis showed that metastasis at diagnosis, poor pathological response, and disease progression (according to the RECIST 1.1 or PERCIST criteria) were all associated with a poor prognosis (p < 0.05). Conclusion Our data indicate that the PERCIST criteria are significantly more sensitive than RECIST 1.1 criteria to identify more responders when evaluating the response of osteosarcoma to neoadjuvant chemotherapy.

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.

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.

The aim of the present study was to evaluate the sensitivity of positron emission tomography/computed tomography (PET/CT) in the diagnosis of giant cell tumor of the bone (GCTB) using the maximum standard uptake value (SUVmax), which indicates the metabolic rate of tissue. Patients diagnosed with pathologically confirmed GCTB between January 2006 and July 2015 were included in the study. Data from PET/CT scans and pathological and clinical reports for all patients were retrospectively reviewed. The SUVmax value from the PET/CT scan of each patient was retrieved and analyzed. A total of 20 patients [12 male and 8 female; age range, 12–45 years; mean age ± standard deviation (SD), 33.5±15.7] with complete PET/CT data and a pathologically and clinically confirmed diagnosis were examined. The SUVmax of GCTB was between 1.8 and 18.6, with a mean ± SD of 9.2±3.8. Although GCTB is not considered to be a malignant lesion, PET/CT scans of the tumors reveal high-grade malignant osseous sarcomas. It is, therefore, important not to mistake such lesions for osteosarcomas or metastatic malignancies of the bone.