Injecting drug use (IDU) is a major risk factor for contracting HIV-1 infection. Both HIV and IDU are neurotoxic, and their coexistence may lead to increased dysfunction of brain metabolic processes. The objective of this research was to investigate the effects of HIV-1 infection and IDU on 18 F-FDG PET brain metabolism. Methods: 18 F-FDG PET brain imaging, with a standard clinical protocol, was performed on 59 subjects who belonged to 3 groups: HIV-positive/IDU-positive (n 5 17), HIV-negative/ IDU-positive (n 5 13), and HIV-negative/IDU-negative controls (n 5 29). A voxel-based analysis of the 18 F-FDG PET brain images was performed using statistical parametric mapping. The images were spatially normalized to a standard 18 F-FDG template, proportionally scaled to compensate for count differences, and then appropriately smoothed. Statistical 2-sample t tests were performed to determine regional metabolic distribution differences in the 3 groups. Results: Diffuse hypermetabolism in the subcortical and deep white matter, the basal ganglia, and the thalami was observed in HIV-1 infection. IDU resulted in increased brainstem metabolism and decreased activity in cortical structures including bilateral medial frontal lobes and the right inferior frontal and temporal cortices. The cortical hypometabolism was more extensive in HIV-1-infected subjects, involving the left temporoparietal and right parietal cortices and bilateral medial frontal lobes. Conclusion: Voxel-based analysis of 18 F-FDG PET brain images demonstrated statistically significant differences in regional metabolism for the 3 studied groups. It also showed that HIV-1 infection may have a synergistic effect with IDU, resulting in more extensive cortical hypometabolism. Correlation of these findings with other quantitative approaches and neurocognitive functioning is warranted.

Radionuclide imaging has proven to be very useful when dealing with neuroendocrine tumors and several radiotracers are currently available. One of the most commonly used and widely accepted methods to image pheochromocytomas is I-131 metaiodobenzylguanidine (MIBG) scintigraphy. However, recent studies with positron emission tomography (PET) using 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) in pheochromocytomas have shown that FDG PET imaging can be useful in those pheochromocytomas (usually malignant) that fail to accumulate MIBG. The therapeutic plan of malignant pheochromocytoma can include chemotherapy and/or a high dose of I-131 MIBG, so precise staging and characterization is mandatory for correct management and treatment.

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