[Influence of visual and auditory masking on the brain glucose metabolism in an idiopathic tinnitus patient].

OBJECTIVE: To study the influence of the audio-visual block (AB) on the brain glucose metabolism of idiopathic tinnitus patients. METHODS: The brain positron emission tomography (PET) test was performed on one chronic idiopathic tinnitus patient under audio-visual block and non-block (NB) conditions respectively. The visual analysis and statistical parameter mapping (SPM) analysis were both used to detect the brain glucose metabolism difference under AB and NB conditions. RESULTS: Under NB conditions, significant hyperactivity was detected at auditory and visual cortex on both sides of the brain. However, this phenomenon was not shown under AB conditions. Instead, a hyperactivity of brain was presented in the left Wernicke's area. CONCLUSIONS: The generation of chronic idiopathic tinnitus probably has no relationship with the auditory cortex abnormity. Wernicke's area might be involved in the central perception of tinnitus.

Efficacy of conventional whole-body ¹8F-FDG PET/CT in the incidental findings of parotid masses.

OBJECTIVE: The objective of this study was to evaluate the incidence of incidental parotid masses with conventional whole-body ¹8F-deoxyglucose (FDG) PET/CT and assess the ability of PET/CT to characterize these unexpected parotid lesions. METHODS: Fifty eight incidental findings of parotid masses with routine FDG PET/CT whole-body scan were reviewed in this retrospective analysis, which were selected from the patients without any known or suspected parotid disease in our PET center, from June 2005 to May 2009. 51 cases were operated or underwent a biopsy after a short-term PET/CT study; the remaining 7 cases had a follow-up. Parotid mass that showed both noncontrast CT (irregular shape and blurry border) and PET malignant features (high FDG uptake, SUV(max) > 3.0) was considered as positive for malignancy. Correlation of FDG PET/CT with histology or follow-up outcome was performed. RESULTS: Fifty eight unexpected findings of parotid masses accounted for 0.3% of the total cases in 4 years, including 11 (19.0%) malignant tumors and 47 (81.0%) benign lesions. 13 lesions manifested single nodule with malignant CT features and intense FDG activity, of which 6 were proved to be malignant; thus, sensitivity and positive predictive values were 54.5% (6 of 11) and 46.2% (6 of 13), respectively. 45 lesions showed either single nodule with benign CT features, or a low FDG uptake (SUV(max) ≤ 3.0), of which 40 were true negatives; therefore, specificity and negative predictive values were 85.1% (40 of 47) and 88.9% (40 of 45), respectively. All parotid masses except 9 benign and 1 malignant showed a high FDG uptake. Compared with SUV only, combined interpretation of PET and CT results displayed a lower sensitivity (90.9-54.5%), but a higher specificity (19.1-85.1%) and a higher overall accuracy. CONCLUSIONS: Whole-body FDG-PET/CT at the time of surveying the entire body condition is helpful for detecting the asymptomatic parotid masses. Combined noncontrast CT is an essential evidence for improving the diagnostic accuracy of FDG-PET/CT for parotid masses.