Clinical significance of suspicious incidental FDG uptake: a comparison between digital PET/CT and conventional PET/CT.

Contribution of Focal 1 8F-FDG Uptake on Positron Emission Tomography/Computed Tomography to Ultrasonography-Based Malignancy Risk Assessment in Incidentally Detected Thyroid Nodules.

AIM The present study sought to evaluate the incremental contribution of the presence of focal FDG uptake and SUVmax on PET/CT in predicting malignancy in incidentally detected thyroid nodules when assessed in conjunction with ultrasonography-based risk features. METHODS In this retrospective study, 304 incidentally detected thyroid nodules identified on PET/CT and confirmed by cytology and/or histopathology were analyzed. The clinical, ultrasonographic, and PET/CT findings were meticulously documented. The presence or absence of focal FDG uptake was subsequently visually assessed on PET/CT images, and SUVmax values were also calculated for FDG-avid nodules. The factors associated with malignancy were evaluated using univariate and multivariate logistic regression analyses. RESULTS The overall malignancy rate was 12.2%. The analysis revealed that focal FDG uptake was observed in 97.3% of malignant nodules and in 65.9% of benign nodules (p < 0.001). Among FDG-avid nodules, SUVmax values were significantly higher in malignant lesions (p < 0.001). However, in multivariate models incorporating ultrasonography-based risk features, focal FDG uptake demonstrated only borderline statistical significance (p = 0.055), while SUVmax was not independently associated with malignancy (p = 0.360). CONCLUSION The absence of focal FDG uptake on PET/CT was associated with a very low likelihood of malignancy in incidentally detected thyroid nodules. However, focal FDG uptake should be interpreted in conjunction with ultrasonography-based risk features rather than as an independent decision-making criterion. Although SUVmax values were higher in malignant FDG-avid nodules, SUVmax did not provide independent or additional diagnostic value beyond ultrasonography-based risk assessment.

Comparative Performance of 18F-FDG PET/CT and 68Ga-FAPI PET/CT in TENIS Syndrome in Treated Differentiated Thyroid Carcinoma.

Objectives Thyroglobulin-elevated negative iodine scintigraphy (TENIS) syndrome presents a significant diagnostic challenge in the management of differentiated thyroid carcinoma (DTC). Although 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is the established imaging modality for detecting presence of structural disease, Gallium-68 (68Ga)-fibroblast activation protein inhibitor (FAPI) PET/CT, which targets the tumor stroma, represents a promising new alternative. This study directly compared the lesion detection capabilities of both tracers in patients with TENIS. Methods In this prospective single-center study (2021-2024), 22 patients with TENIS syndrome underwent both 18F-FDG and 68Ga-FAPI PET/CT scans within a 7-day interval of each other. Lesion detectability and maximum standardized uptake values (SUVmax) were compared between the two modalities. Lesions were validated using histopathology or cytopathology, biochemical response to empirical 131I therapy, imaging correlation or progression, and clinical progression methods. Results Among 22 patients (median age 43.5 years, 90% with papillary carcinoma), 18F-FDG was positive in 23/33 cervical lymph nodes, whereas 68Ga-FAPI was positive in 14/33 lymph nodes. Fourteen lymphnodes were positive on both modalities with comparable SUVmax (median 18F-FDG 3.3 vs. 68Ga-FAPI 3.6, p=0.689). All local recurrences in thyroid bed (n=4) were 18F-FDG-positive, whereas only 3 of the local recurrences were 68Ga-FAPI-positive. Distant metastases (lung and bone) showed similar detection rates. Conclusion 18F-FDG PET/CT demonstrates superior lesion detectability, particularly for cervical lymph nodes, in TENIS syndrome. 68Ga-FAPI PET/CT provides complementary information with comparable semiquantitative uptake in detected lesions but with lower overall detection. 18F-FDG PET/CT remains the preferred imaging modality for comprehensive disease evaluation in patients with radioactive iodine-refractory DTC.

The Role of F-18 FDG PET/CT in the Evaluation of Solitary Pulmonary Nodules

Summary Objective: Fluorine-18 fluorodeoxyglucose positronemissiontomography/computedtomography (F-18 FDG PET/CT) is commonly used in the evaluation of solitary pulmonary nodules (SPNs). This study aimed to investigate the predictive value of maximum standardized uptake value (SUVmax) and its ratios to liver and mediastinal blood pool SUVmax values for malignancy in SPNs, using histopathological findings as the reference standard. Methods: The study included 130 patients who underwent F-18 FDG PET/CT and had either histopathological confirmation or at least two years of radiological follow-up. Demographic data (age and sex), nodule size, location, contour characteristics, nodule SUVmax, nodule-to-liver SUVmax ratio (NLR), and nodule-to-mediastinal blood pool SUVmax ratio (NBR) were recorded. Nodules were classified as benign or malignant based on histopathological results. Results: Among the 83 patients with histopathological diagnosis, 54% (n = 44) had malignant lesions and 46% (n = 39) had benign lesions. The mean size of malignant nodules was approximately 20 mm. Receiver operating characteristic (ROC) analysis demonstrated that an SUVmax cutoff value of 4.02 provided the highest diagnostic accuracy for predicting malignancy. Both NLR and NBR showed significant diagnostic value in malignancy prediction. These parameters demonstrated high sensitivity (84–91%) and negative predictive value (76–84%), indicating their usefulness in excluding benign nodules. Conclusion: The F-18 FDG PET/CT is a valuable imaging modality in the evaluation of solitary pulmonary nodules. In addition to SUVmax, the use of NLR and NBR may improve diagnostic accuracy and contribute to clinical decision-making.

Evaluation of Cavitary Lung Lesions with 18F-FDG PET/CT: Differentiating Benign from Malignant Lesions.

Objectives This study aimed to analyze 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) features to differentiate benign from malignant pulmonary cavitary lesions. Methods A total of 76 patients with cavitary lung lesions who underwent 18F-FDG PET/CT imaging were retrospectively analyzed. Patient demographics, histopathological findings, cavitary lesion morphology, CT characteristics, and maximum standard uptake value (SUVmax) of lesions were recorded. Cavitary lesions were classified as benign or malignant and further subdivided by maximum wall thickness into two groups: ≤15 mm and >15 mm. Histopathological results, clinical follow-up, or both were used as the reference standard for lesion classification. Results Among 76 patients (mean age, 63.4 years), 31 (40.8%) had benign disease and 45 (59.2%) had malignant disease. Malignant lesions were observed at older ages and exhibited significantly greater lesion size, wall thickness, and SUVmax than those in benign lesions (p<0.05 for all). There were no significant differences between the malignant and benign groups regarding sex, lesion localization, air-fluid levels, or pleural effusion (p>0.05 for all). Peripheral consolidation, multiple cavitary lesions, and tree-in-bud pattern were significantly more prevalent in benign lesions than in malignant lesions (p<0.05 for all). In lesions with a maximum wall thickness ≤15 mm, SUVmax was significantly higher in malignant lesions than in benign lesions (mean values, 9.81 vs. 5.28; p<0.05). Malignant lesions with a maximum wall thickness >15 mm demonstrated higher SUVmax values (mean 18.37 vs. 10.45; p<0.05). SUVmax was independently associated with malignancy (odds ratio: 1.237, p=0.017) and showed the best diagnostic performance (area under the curve=0.866; cut-off 8.58, sensitivity 80%, specificity 77%). Conclusion The morphological characteristics of pulmonary cavitary lesions, associated parenchymal findings, and 18F-FDG uptake patterns on PET/CT provide valuable information for distinguishing between benign and malignant lesions. In this study, SUVmax demonstrated the highest diagnostic performance. The combined evaluation of metabolic and morphological parameters can enhance diagnostic accuracy and support the clinical decision-making process, thereby contributing to the optimal management of patients.

18F-FDG PET/MRI for non-invasive risk stratification of Intraductal Papillary Neoplasms of the Bile Duct (IPNB).

Diagnostic Accuracy of Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Differentiating Tumor and Bland Thrombus in Patients With Cancer: A Systematic Review and Meta-Analysis.

INTRODUCTION Differentiating tumor thrombus from bland thrombus can be challenging. This study assessed the diagnostic performance of positron emission tomography-computed tomography (PET/CT) scans in differentiating bland versus tumor thrombi in patients with cancer. METHODS We systematically searched for observational studies evaluating the diagnostic accuracy of PET/CT scans in differentiating tumor from bland thrombi in adult cancer patients. We included patients with suspected tumor or bland thrombus on PET/CT who underwent histopathological evaluation and/or confirmatory imaging or clinical follow-up. Sensitivity and specificity were estimated using a random-effects model. Positive and negative likelihood ratios (LR+ and LR-) and diagnostic odds ratio (DOR) were derived from the pooled estimates. RESULTS Five studies were included (217 patients; mean age 55.9 years). Hepatobiliary malignancies (49%) and renal tumors (24%) were the most frequent, with the renal vein, portal vein, and inferior vena cava most frequently involved. Maximum standardized uptake value (SUVmax) was significantly higher in malignant compared to bland thrombi, with reported diagnostic cutoffs ranging from 2.25 to 3.63. PET/CT scan showed diagnostic accuracy with pooled sensitivity 92.2%, specificity 94.2%, LR- 0.121, LR+ 10.919, and DOR of 91.770. CONCLUSION PET/CT scan may be beneficial in distinguishing tumor from bland thrombus in cancer patients.