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Objective To evaluate 18F-fluorodeoxyglucose (FDG) PET/CT in detecting occult malignancy in patients with suspected paraneoplastic neurological syndrome (PNS).Methods Twenty consecutive patients who underwent PET/CT scanning with the indication of suspected PNS were retrospectively reviewed.The gold standard of PNS was either cytology or clinical follow-up, and the final diagnosis was compared with PET/CT findings.Results Of the 20 patients, six were PNS.PET/CT detected nine cases.Six were true positive and three were false positive.The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of PET/CT were 100% (6/6), 78.57% (11/14), 85.00% (17/20),66.7% (6/9) and 100.00% ( 11/11 ) respectively.The treatment plan was modified based on the PET/CT results in 4 patients.Conclusions 18F-FDG PET/CT may play a role in detecting the underlying malignancy of PNS.It is also valuable in staging of the malignancy thus providing information for therapy decision making.
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<p><b>OBJECTIVE</b>To evaluate the value of (18)F-FDG and (11)C-MET PET-CT scan in differentiation of brain ringlike-enhanced lesions on MRI imaging.</p><p><b>METHODS</b>Forty-one brain ringlike-enhanced lesions on MRI imaging including 30 brain tumors and 11 non-neoplastic lesions confirmed pathologically or clinically underwent (18)F-FDG and (11)C-MET PET-CT brain scan. Among them, 15 patients who were suspected to have brain metastasis received body scan by (18)F-FDG PET-CT. Both images were analyzed visually and semi-quantitatively.</p><p><b>RESULTS</b>Visual analysis: for brain tumors the diagnostic sensitivity, specificity and accuracy of (18)F-FDG PET-CT was 53.3%, 72.7%, 58.5%, versus 96.7%, 90.9%, 95.1% of (11)C-MET PET-CT, respectively. All the primary foci in 9 patients with brain metastases were detected by body (18)F-FDG PET-CT scan. Semiquantitative analysis: There was a significant difference in the uptake between highly differentiated malignant and poorly differentiated tumors as well as non-neoplastic lesions for both tracers (P < 0.01), while between low-grade malignant tumors and non-neoplasm lesions, there was a difference in uptake only by (11)C-MET (P < 0.01). No significant difference between the uptakes in brain metastasis and glioblastomas was found by both tracers (P > 0.05).</p><p><b>CONCLUSION</b>Both (18)F-FDG and (11)C-MET PET-CT are useful in differentiation of brain ringlike-enhanced lesions on MRI imaging. (11)C-MET PET-CT is more helpful than (18)F-FDG PET-CT in differential diagnosis of low-grade neoplastic from non-neoplastic lesions. Combination of (18)F-FDG and (11)C-MET PET-CT scans can improve the accuracy of differential diagnosis for brain ringlike-enhanced lesions on MRI imaging.</p>