The hippocampus is one of the earliest sites involved in the pathology of Alzheimer's disease (AD). Therefore, we specifically investigated the sensitivity and specificity of hippocampal volume and glucose metabolism in patients being evaluated for AD, using automated quantitative tools (NeuroQuant – magnetic resonance imaging [MRI] and Scenium – positron emission tomography [PET]) and clinical evaluation.This retrospective study included adult patients over the age of 45 years with suspected AD, who had undergone fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET-CT) and MRI. FDG-PET-CT images were analyzed both qualitatively and quantitatively. In quantitative volumetric MRI analysis, the percentage of the total intracranial volume of each brain region, as well as the total hippocampal volume, were considered in comparison to an age-adjusted percentile. The remaining brain regions were compared between groups according to the final diagnosis.Thirty-eight patients were included in this study. After a mean follow-up period of 23 ± 11 months, the final diagnosis for 16 patients was AD or high-risk mild cognitive impairment (MCI). Out of the 16 patients, 8 patients were women, and the average age of all patients was 69.38 ± 10.98 years. Among the remaining 22 patients enrolled in the study, 14 were women, and the average age was 67.50 ± 11.60 years; a diagnosis of AD was initially excluded, but the patients may have low-risk MCI. Qualitative FDG-PET-CT analysis showed greater accuracy (0.87), sensitivity (0.76), and negative predictive value (0.77), when compared to quantitative PET analysis, hippocampal MRI volumetry, and specificity. The positive predictive value of FDG-PET-CT was similar to the MRI value.The performance of FDG-PET-CT qualitative analysis was significantly more effective compared to MRI volumetry. At least in part, this observation could corroborate the sequential hypothesis of AD pathophysiology, which posits that functional changes (synaptic dysfunction) precede structural changes (atrophy).

Objective: To evaluate whether there is a significant difference in somatostatin analog uptake in meningiomas treated or not with radiation therapy. Methods: A cross-sectional study was performed comparing measurements of somatostatin analog ( 68 Ga-DOTATATE) uptake in two independent groups of ten patients each -one consisting of patients with meningiomas previously treated with radiation therapy and another comprising patients who had never been submitted to radiation therapy. All patients underwent PET/CT and MRI scans in an interval shorter than 24 hours between exams. Results: A total of 32 meningiomas from 20 patients were analyzed, all presenting significant somatostatin analog uptake in different degrees. The uptake levels of somatostatin analog were similar between the lesions treated or not with radiation therapy, and the mean values of SUV max were 27.62 and 24.82, respectively (p=0.722). For SUV mean , the values were 16.20 and 14.82, respectively (p=0.822). Conclusion: Comparative analysis between the groups showed no significant differences in degree of somatostatin analog uptake in successfully irradiated and non-irradiated meningiomas.

Background: Autoimmune encephalitis (AIE) is the main differential diagnosis of infectious encephalitis. Brain MRI is normal in up to 50% of cases and studies indicate that changes in FDG-PET/CT are more frequent and early. Objectives: To describe FDG-PET/CT findings in patients with AIE of Hospital Israelita Albert Einstein (HIAE) from 2015-2020. Design and setting: Retrospective cross-sectional study at HIAE. Methods: Medical records of patients with suspected AIE were reviewed. Laboratory results were compiled, and images were reassessed. Results: Amongst 250 records, we found 7.6% (n=19) of AIE, being 8 seropositive (5 anti-NMDA, 1 anti-CASPR2, 1 anti-MOG, 1 anti-VGKC and 1 anti-LGI1), 5 seronegative and 4 limbic encephalitis. The mean age was 48-22 years, 52% male. In encephalitic patients, the most common manifestations were epilepsy (78%), cognitive changes (63%), and behavioral changes (63%). Only 57% had abnormal MRI. We evaluated 23 PET/CTs at different stages of treatment; of the 9 FDG-PET/CTs performed at initial presentation, 88% were abnormal and 30% had normal MRI. Most frequent patterns found were hypometabolism in frontal (59.1%), temporal (39.1%) and left parietal (39.1%) regions. In follow-up, only 2 patients normalized FDG-PET/CT, with clinical improvement. Conclusions:FDG-PET/CT was altered in 88% of patients. In this series, no typical PET/CT pattern was demonstrated for AIE; the most frequent findings were hypometabolism in cortical areas, which also occur in degenerative diseases. We did not find hypermetabolism, or mixed areas of hypo- and hypermetabolism. The specificity of PET/CT for AIE diagnosis should be evaluated in future studies.