Introduction
Cerebral glucose metabolism is closely linked to neuronal and synaptic function in health and disease. Several brain pathologies result in neuronal and synaptic changes, consequently leading to altered glucose metabolism. 2-[18F] fluoro-2-deoxy-D-glucose (18F-FDG) PET/CT imaging is used to assess metabolic brain function. The spatial resolution of current digital total-body PET/CT machines, without the need for specific brain PET devices, provides fast images of brain metabolism with outstanding, previously unattainable image resolution. This impressive image resolution has, in recent years, given momentum to further integrate 18-F FDG PET/CT into the clinical management of several neurological conditions, particularly in the differential diagnosis of dementia or other neurodegenerative disorders.
Scan Technique
Brain 18 F-FDG PET/CT images were obtained using a Siemens Healthineers Biograph Vision digital PET/CT machine. The images were acquired 60 minutes after intravenous administration of 10 mCi of 18F-FDG in a quiet room with dim lighting and closed eyes. The images were acquired using a 440-matrix, zoom 2, and raw data were reconstructed using iterative reconstruction with TOF (time of flight). The images were displayed in axial, coronal, and sagittal views using the French rainbow color scale. Scenium neuroanalysis software was applied to processed data to generate statistical parametric mapping of brain glucose metabolism.
Case study 1
A 73-year-old female patient, a known case of diabetes mellitus and hypertension, presented with headache, dizziness, and a deterioration in cognitive function with retrograde and antegrade amnesia over a few months. 18 F-FDG PET/CT (Row A) demonstrated markedly reduced metabolic activity involving the frontal lobes, posterior parietal areas, in particular at the precuneus, posterior cingulate gyrus, and temporal lobes, being most evident on the left side. The pattern is consistent mostly with Alzheimer’s disease. (Row B) is the statistical parametric mapping of 18 F-FDG PET/CT demonstrating markedly reduced metabolic activity involving parietal and temporal lobes displayed as dark blue, with mildly reduced metabolic activity involving frontal lobes evident as light green or yellow.
Case study 2
A 66-year-old male patient presented with recent loss of memory, visuospatial disorientation, and personality changes. MRI revealed age-related cerebral involutional changes manifested as mild dilatation of the ventricular system and extraxial CSF spaces. 18 F-FDG PET/CT (Row A) demonstrated moderately and almost symmetrically reduced cortical metabolic activity involving the frontal and temporal lobes bilaterally, whereas metabolic activity of the parietal lobes is preserved, particularly at the precuneus. The pattern is mostly consistent with frontotemporal dementia. (Row B) is the statistical parametric mapping of 18 F-FDG PET/CT, confirming moderately reduced metabolic activity involving frontal and temporal lobes bilaterally, displayed in yellow and green colors, whereas parietal lobes demonstrate excellent activity displayed in red color.
Case study 3
A 66-year-old male patient presented with recent loss of memory, visuospatial disorientation, and personality changes. MRI revealed age-related cerebral involutional changes manifested as mild dilatation of the ventricular system and extraxial CSF spaces. 18 F-FDG PET/CT (Row A) demonstrated moderately and almost symmetrically reduced cortical metabolic activity involving the frontal and temporal lobes bilaterally, whereas metabolic activity of the parietal lobes is preserved, particularly at the precuneus. The pattern is mostly consistent with frontotemporal dementia. (Row B) is the statistical parametric mapping of 18 F-FDG PET/CT, confirming moderately reduced metabolic activity involving frontal and temporal lobes bilaterally, displayed in yellow and green colors, whereas parietal lobes demonstrate excellent activity displayed in red color.
Case study 3
A 71-year-old male patient with renal failure on hemodialysis presented with loss of upward gaze and double vision for a few months. No abnormality was detected on ophthalmology and ENT examination. On neurological examination, he had loss of eye convergence and a positive incoordination test. MRI revealed a prominent ventricular system and extra-axial spaces with generalized loss of brain volume. No significant white matter disease was seen, and no acute territorial infarction was present. 18 F-FDG PET/CT (Column A) demonstrated markedly abnormal reduced metabolic activity involving the prefrontal cortex bilaterally, more evident on the left side, both caudate nuclei, midbrain, and cerebellum. 18 F-FDG PET/CT findings are consistent with Progressive Supranuclear Palsy with the Hummingbird sign. (Column B)
Case study 4
A 13-year-old boy presented with intractable generalized tonic-clonic epilepsy since the age of 5 years. EEG revealed abundant discharges over the temporal-central head region, whereas MRI was normal on several occasions (Column A). 18 F-FDG PET/CT demonstrated an area of abnormally reduced metabolic activity involving the anterior pole of the right middle temporal lobe, suggestive of an epileptic focus (Column B).