Comparing to the conventional PET/CT, the advantage of total-body PET/CT lies in the long axial field-of-view (LAFOV) which improves the system sensitivity by 40 times, allowing rapid scan, low-dosing imaging and total-body dynamic imaging. Total-body PET/CT can increase the throughput of patients, reduce the radiation dose, and observe the drug metabolism in vivo both real-time and dynamically. Its high sensitivity makes long-time delay scan possible in clinic research. Besides, it also has potential advantages in drugs development and in the field of pharmacokinetic researches.

Objective:To investigate the value of total-body PET/CT 2 h imaging with half-dose 18F-FDG in the detection of active lesions of Takayasu arteritis (TA). Methods:Fifty-five patients with TA(13 males, 42 females, age: (34.3±13.9) years), who accepted 2 h total-body 18F-FDG PET/CT scan with half-dose activity in Zhongshan Hospital, Fudan University between January 2020 and June 2021, were retrospectively enrolled. TA was diagnosed according to the American College of Rheumatology (ACR) criteria. Patients were categorized into active TA group and inactive TA group based on the National Institutes of Health (NIH) criteria. Lesions with SUV max≥(liver SUV max- 0.1) were defined as active lesions. If multiple lesions occurred in one artery segment, only the lesion with the highest SUV max was chosen. Lesion-to-blood SUV max ratio was calculated. The independent-sample t test or Mann-Whitney U test was used to analyze the liver SUV max, blood pool SUV max and lesion-to-blood ratio between those 2 groups. Results:A total of 363 active lesions were found in 39 patients with active TA and 137 lesions were found in 16 patients with inactive TA. The liver SUV max (1.93±0.45 vs 1.95±0.35; t=0.20, P=0.846) and blood pool SUV max (0.75(0.63, 0.98) vs 0.90(0.77, 1.01); z=-1.45, P=0.148) of patients with active and those with inactive TA were not significantly different. The lesion-to-blood ratio in active TA group was higher than that in inactive TA group (3.09(2.36, 4.24) vs 2.57(2.24, 3.25); z=4.05, P<0.001). Conclusions:Total-body PET/CT 2 h imaging has qualified lesion-to-blood ratio in TA imaging. Inflammatory lesions of vascular wall can be detected sensitively in both patients with active TA and those with inactive TA.

Objective:To explore the added value of time-activity curve (TAC) and target-to-background ratio (TBR) obtained by 18F-FDG total-body PET/CT dynamic imaging in the diagnosis of liver malignant tumors. Methods:From December 2019 to October 2021, 109 patients (65 males, 44 females; age (59.3±9.3) years) with hepatocellular carcinoma (HCC; n=27), intrahepatic cholangiocarcinoma (ICC; n=61) and colorectal cancer with liver metastasis (CRLM; n=21) who underwent 60 min 18F-FDG total-body PET/CT dynamic imaging in Zhongshan Hospital, Fudan University were retrospectively enrolled. Dynamic PET/CT images were divided into perfusion-weighted (PW) phase and metabolism-weighted (MW) phase. The arterial phase was defined as the 15 s after the abdominal aorta peak frame at PW. TACs at MW were divided into three types as Graph A, Graph B and Graph C. One-way analysis of variance was used to compare difference of TBR 30/60 among groups. ROC curve analysis was used to evaluate diagnostic effectiveness. Results:With hypervascularity as the diagnostic standard of HCC, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 66.7%(18/27), 75.6%(59/78), 48.6%(18/37) and 86.8%(59/68), respectively. With Graph B as the diagnostic standard of HCC, the sensitivity, specificity, PPV and NPV were 44.4%(12/27), 85.4%(70/82), 50.0%(12/24) and 82.4%(70/85), respectively. The TBR 30/60 of HCC, ICC and CRLM was 0.38±0.19, 0.49±0.18 and 0.64±0.20 respectively ( F=10.89, P<0.001). When the cut-off value of TBR 30/60 was 0.43, the AUC of distinguishing HCC from ICC and CRLM was 0.72, with the sensitivity and specificity of 70.5%(55/78) and 65.2%(15/23). When the cut-off value of TBR 30/60 was 0.64, the AUC of distinguishing ICC from CRLM was 0.71, with the sensitivity and specificity of 61.9%(13/21) and 82.5%(47/57). Conclusion:TAC graph types and TBR 30/60 obtained by total-body PET/CT dynamic imaging display potential value for differentiation between hepatic tumor types.