Introduction
flowchart TD
Pet["Pet"] -->|"biomarker for"| Parkinson_s_Disease["Parkinsons Disease"]
PET["PET"] -->|"regulates"| MOLECULAR_IMAGING["MOLECULAR_IMAGING"]
style PET fill:#4fc3f7,stroke:#333,color:#000
Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is a molecular imaging technique that measures cerebral glucose metabolism, providing critical information about neuronal function and health in neurodegenerative diseases. FDG-PET is essential for differential diagnosis of [dementias](/diseases/dementia-lewy-bodies), [Parkinsonism](/diseases/parkinsons-disease), and [atypical parkinsonian syndromes](/diseases/atypical-parkinsonism)[@minsheny2011][@foster2007].
Principles of FDG-PET
How FDG-PET Works
Radiotracer administration : [18F]FDG (fluorodeoxyglucose) is injected intravenouslyGlucose uptake : FDG is taken up by cells via glucose transporters (GLUT)Phosphorylation : Hexokinase phosphorylates FDG, trapping it in cellsPositron emission : 18F decays, releasing positronsDetection : PET scanner detects annihilation photon pairsReconstruction : Images showing regional glucose metabolism are created
Neuronal activity indicator : Glucose is the primary energy source for neuronsSynaptic function : Metabolism reflects synaptic activityEarly detection : Metabolic changes precede structural atrophyDisease-specific patterns : Different disorders show distinct hypometabolism patternsClinical Applications ...
Introduction
Mermaid diagram (expand to render)
Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is a molecular imaging technique that measures cerebral glucose metabolism, providing critical information about neuronal function and health in neurodegenerative diseases. FDG-PET is essential for differential diagnosis of [dementias](/diseases/dementia-lewy-bodies), [Parkinsonism](/diseases/parkinsons-disease), and [atypical parkinsonian syndromes](/diseases/atypical-parkinsonism)[@minsheny2011][@foster2007].
Principles of FDG-PET
How FDG-PET Works
Radiotracer administration : [18F]FDG (fluorodeoxyglucose) is injected intravenouslyGlucose uptake : FDG is taken up by cells via glucose transporters (GLUT)Phosphorylation : Hexokinase phosphorylates FDG, trapping it in cellsPositron emission : 18F decays, releasing positronsDetection : PET scanner detects annihilation photon pairsReconstruction : Images showing regional glucose metabolism are created
Neuronal activity indicator : Glucose is the primary energy source for neuronsSynaptic function : Metabolism reflects synaptic activityEarly detection : Metabolic changes precede structural atrophyDisease-specific patterns : Different disorders show distinct hypometabolism patternsClinical Applications
Alzheimer's Disease
Characteristic FDG-PET Pattern
Posterior cingulate hypometabolism : Early and prominent findingPrecuneus hypometabolism : Central to AD pathophysiologyTemporoparietal hypometabolism : Especially posterior temporalFrontal metabolism : Variable, often preserved earlyClinical Utility
Early detection : Can identify AD years before symptomsDifferential diagnosis : Distinguishes AD from other dementiasPrognostication : Hypometabolism predicts progressionTreatment monitoring : Metabolic changes with therapyFrontotemporal Dementia FTD subtypes show distinct patterns[@foster2007]:
| FTD Variant | Hypometabolism Pattern |
Dementia with Lewy Bodies
Occipital hypometabolism : Posterior cingulate often sparedPrimary visual cortex : Reduced metabolismPattern distinguishes from AD : Less posterior cingulate involvementUseful for DLB vs. AD differentiation Parkinson's Disease and Atypical Parkinsonism
Parkinson's Disease
Presynaptic dopaminergic imaging : More commonly used than FDGMetabolic patterns : Less characteristic than in atypical parkinsonismCognitive impairment : Posterior cortical hypometabolismMultiple System Atrophy
Brainstem/cerebellar hypometabolism : CharacteristicStriatal hypometabolism : Putamen more than caudateCerebellar atrophy pattern : In MSA-C variantProgressive Supranuclear Palsy
Midbrain hypometabolism : Most characteristic findingFrontal cortex : Reduced metabolismSuperior cerebellar peduncle : Decreased activityDifferential from PD : Midbrain vs. striatal patternsCorticobasal Syndrome
Asymmetric cortical hypometabolism : Contralateral to more affected sideFrontal and parietal : Most affectedBasal ganglia : Often involvedCorpus callosum : Reduced metabolism[@kawasaki2016]Comparative Patterns
Differential Diagnosis Matrix | Disease | Posterior Cingulate | Occipital | Frontal | Temporal | Striatum | Brainstem |
Legend: ↓↓ = severely reduced, ↓ = reduced, ↔ = preserved
Technical Considerations
Acquisition Protocol
Fasting : 4-6 hours before injectionRadiotracer dose : 185-370 MBq (5-10 mCi)Uptake period : 30-45 minutesScan duration : 15-30 minutesReconstruction : OSEM or filtered backprojection
Quantification Methods
Standardized Uptake Value (SUV) : Normalized to body weightSUVr (SUV ratio) : Relative to reference regionStatistical parametric mapping (SPM) : Voxel-wise comparisonsPCA (principal component analysis) : Pattern recognitionReference Regions
Cerebellum : Often used for normalizationPons : Common reference for cortical ratiosWhole brain : For global metabolismSpecific regions : Disease-dependent choiceClinical Implementation
Diagnostic Algorithm
Clinical assessment : Initial neurological evaluationFDG-PET ordered : For uncertain diagnosisPattern interpretation : Disease-specific hypometabolismIntegration with other findings : Imaging, CSF, genetics
Advantages Over Other Imaging
Metabolic information : Functional vs. structuralEarly detection : Before atrophy on MRIPattern specificity : Different diseases show different patternsQuantitative : Objective measuresLimitations
Radiation exposure : Though lower than CTCost : Higher than SPECTAccessibility : Fewer PET scanners than MRINon-specificity : Some pattern overlap between diseasesResearch Applications
Biomarker Development
AD progression : Metabolic decline tracks clinical declinePreclinical AD : Hypometabolism in normal-appearing brainTreatment trials : Endpoint measure for disease-modifying therapiesGenetic forms : Metabolic patterns in familial AD, FTDFDG-PET in Clinical Trials
Enrollment criteria : Ensuring correct diagnosisOutcome measures : Change in metabolismMechanistic insights : Drug effects on brain metabolismBiomarker validation : Against other markersEmerging Developments
Hybrid Imaging
PET/MRI : Combined functional and structuralPET/CT : Anatomical localizationSimultaneous acquisition : Better registrationAutomated Analysis
Machine learning : Pattern classificationDeep learning : Automated diagnosisRadiomics : Feature extractionPredictive modeling : Individual prognosisNew Tracers
Amyloid PET : Pittsburgh compound B (PiB)Tau PET : FLTAU, AV-1451Dopamine tracers : More specific targetingSynaptic density : SV2A ligandsReferences
[Minshen et al., FDG PET in neurodegenerative brain diseases (2011)](https://doi.org/10.2967/jnumed.110.085175)
[Foster et al., FDG-PET and dementia (2007)](https://doi.org/10.1007/s00259-007-0477-3)
[Niethammer et al., Neuroimaging in Parkinson's disease (2010)](https://doi.org/10.1016/j.nicl.2010.04.004)
[Kawasaki et al., FDG-PET in atypical parkinsonism (2016)](https://doi.org/10.1016/j.jns.2016.02.046)
[Silverman, Defining the clinical syndrome of Alzheimer's disease (2002)](https://doi.org/10.1016/S0197-4582(02)00037-4)
Related Pages
[PET Imaging](/technologies/pet-imaging)](/technologies)
[SPECT Imaging](/technologies/spect)](/technologies)
[MRI for Neurodegenerative Diseases](/technologies/magnetic-resonance-imaging)](/technologies)
[FDG-PET in CBS](/diagnostics/metabolic-imaging-pet-cbs-psp)](/diagnostics)
[Alzheimer's Disease Diagnosis](/diseases/alzheimers-disease)
[Parkinson's Disease Diagnosis](/diseases/parkinsons-disease)](/proteins/parkin)
[Corticobasal Syndrome](/diseases/corticobasal-syndrome)
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