Objective: To evaluate the diagnostic performance of combined multiparametric ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸FDG PET) with clinical characteristics in differentiating thymic epithelial tumors (TETs) from thymic lymphomas. Patients and methods: A total of 173 patients with 80 TETs and 93 thymic lymphomas who underwent ¹⁸F-FDG PET/CT before treatment were enrolled in this retrospective study. All patients were confirmed by pathology, and baseline characteristics and clinical data were also collected. The semi-parameters of ¹⁸F-FDG PET/CT, including lesion size, SUVmax (maximum standard uptake value), SUVmean (mean standard uptake value), TLG (total lesion glycolysis), MTV (metabolic tumor volume) and SUVR (tumor-to-normal liver standard uptake value ratio) were evaluated. The differential diagnostic efficacy was evaluated using the receiver operating characteristic (ROC) curve. Integrated discriminatory improvement (IDI) and net reclassification improvement (NRI), and Delong test were used to evaluate the improvement in diagnostic efficacy. The clinical efficacy was evaluated by decision curve analysis (DCA). Results: Age, clinical symptoms, and metabolic parameters differed significantly between patients with TETs and thymic lymphomas. The ROC curve analysis of SUVR showed the highest differentiating diagnostic value (sensitivity = 0.763; specificity = 0.888; area under the curve [AUC] = 0.881). The combined diagnostics model of age, clinical symptoms and SUVR resulted in the highest AUC of 0.964 (sensitivity = 0.882, specificity = 0.963). Compared with SUVR, the diagnostic efficiency of the model was improved significantly. The DCA also confirmed the clinical efficacy of the model. Conclusions: The multiparameter diagnosis model based on ¹⁸F-FDG PET and clinical characteristics had excellent value in the differential diagnosis of TETs and thymic lymphomas.

To examine the prognostic value of fluorodeoxyglucose (FDG) and fluorothymidine (FLT) interim positron emission tomography/computed tomography (PET/CT) for diffuse large B cell lymphoma (DLBCL). Forty-four patients with newly diagnosed DLBCL underwent both 18F-FDG and 18F-FLT PET/CT scans at baseline and after two cycles of a rituximab-containing chemotherapy regimen. Maximum standard uptake values (SUVmax) and changes in SUV (ΔSUV) were calculated for both tracers for the predominant lesion of each patient, for prediction of progression free survival (PFS) and overall survival (OS). The median follow-up period was 71 months. Receiver operating characteristic analysis indicated that the best ΔSUV cut-off values for FDG (ΔSUVFDG) and FLT (ΔSUVFLT) were 79% and 76%, respectively. A ΔSUVFLT cut-off of 76% had the highest significance for prediction of PFS (p=0.003) and OS (p=0009), with sensitivity, specificity, and accuracy of 80.0%, 85.7%, and 81.8% respectively in response assessment. Interim FLT PET/CT had higher specificity and accuracy than standard FDG PET/CT-based interpretation. This study demonstrated that interim FLT PET/CT had higher accuracy than standardized FDG-based interpretation for therapeutic response assessment in DLBCL. FLT had the advantage of potentially reducing false positive of interim FDG PET/CT.

Background: This retrospective study was performed to estimate the clinical role of whole-body positron emission tomography/computed tomography (PET/CT) using 2-[¹⁸F] fluoro-2-deoxy-D-glucose (FDG) in the differential diagnosis of primary benign and malignant unilateral adrenal tumors. Methods: A total of 64 patients (31 male, 33 female; age range: 3–76 years, mean: 48.5) with a confirmed unilateral adrenal tumor underwent ¹⁸F-FDG PET/CT examination for diagnosis and staging. The whole-body ¹⁸F-FDG PET/CT examination excluded metastasis, and all patients were confirmed by operation and biopsy pathology. Their clinical data and pathological results were collected. On visual analysis of PET/CT imaging, adrenal uptake was based on a three-scale grading system. The region of interest (ROI) was delineated in the liver and the renal lesion site. Standardized uptake value (SUV) measurements were determined on a standardized reconstruction, and the maximum values (SUV_max) of the lesion and liver were measured. The ratio of tumor to the liver was defined as T/L. Visual interpretation, SUV_max-receiver operating characteristics (ROC) method, and T/L-ROC method were used to analyze the diagnostic accuracy. Results: A total of 64 lesions (48 benign, 16 malignant lesions) were detected. The visual analysis found that 100% of Grade I cases were benign, 90.9% of Grade II cases were benign, and 65.1% of Grade III cases were benign. The SUV_max of malignant lesions (10.0±5.8) was higher than that of benign lesions (5.4±5.3, P<0.05). The T/L was 3.39±1.79 for malignant lesions and 1.99±2.09 for benign lesions (P<0.05). In the differentiation of primary benign and malignant unilateral adrenal tumors, the sensitivity, specificity, and accuracy of the SUV_max-ROC method (cut-off value =5.65) were 81.25%, 72.91%, 75.00%, and the positive and negative predictive values were 50.00% and 92.11%, respectively. The sensitivity, specificity, and accuracy of the T/L-ROC method (cut-off value =1.52) were 93.73%, 62.50%, 70.31%, and the positive and negative predictive values were 46.88% and 96.77%, respectively. Conclusions: ¹⁸F-FDG PET/CT improved diagnostic accuracy in differentiating primary benign and malignant unilateral adrenal tumors. There was a high negative predictive value, and for positive prediction, other tracer imaging is needed for differential diagnosis.

Objective. To evaluate ¹⁸F‐fluorodeoxyglucose positron emission tomography (¹⁸FDG PET) and clinical parameters to differentiate rheumatoid arthritis (RA) and polymyalgia rheumatic (PMR). Patients and Methods. This retrospective study evaluated 54 patients with suspected RA (n = 23) and PMR (n = 31) who underwent ¹⁸F‐FDG PET/CT before treatment. The complete diagnosis was based on each classification criterion and at least followed up for 6 months. Demographic and clinical data were also collected. Semiquantitative analysis (maximum standardized uptake value, SUVmax) of abnormal ¹⁸F‐FDG uptake was undertaken at 17 musculoskeletal sites, and two scoring systems (mean reference (liver/control) scores) were evaluated. The differential diagnostic efficacy of each independent parameter was evaluated using the receiver operating characteristic (ROC) curve. Integrated discriminatory improvement (IDI) and bootstrap tests were used to evaluate the improvement in diagnostic efficacy using a combination of multiple parameters. Results. The ROC curve analysis of SUVmax indicated that the interspinous ligament showed the highest discriminative diagnostic value (sensitivity, 64.5%; specificity, 78.3%; area under the curve (AUC), 0.764; positive predictive value, 0.800; negative predictive value, 0.621). The combined model with the rheumatoid factor (RF) and metabolic parameters of ¹⁸F‐FDG PET resulted in the highest AUC of 0.892 and showed significant reclassification by IDI (IDI, 9.51%; 95% confidence interval: 0.021–0.175; P = 0.013). According to the bootstrap test, compared with RF alone, the combination of RF and metabolic parameters showed an improvement in ROC and was statistically significant (P = 0.017). Conclusions. The combination of ¹⁸F‐FDG PET metabolic and clinical parameters can further improve the differential diagnosis of RA and PMR.

Quantitative analysis of ⁶⁸Ga-DOTA(0)-Tyr(3)-octreotate positron emission tomography/computed tomography imaging for the differential diagnosis of primary pheochromocytoma and paraganglioma Guangyu Ma, Jin Du, Xiaojun Zhang, Jiajin Liu, Xiaodan Xu, Baixuan Xu, Zhiwei Guan

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