Positron Emission Tomography (PET) imaging is a powerful molecular imaging technique that enables visualization and quantification of pathological processes in the living brain. PET has become indispensable for diagnosing neurodegenerative diseases, tracking disease progression, and evaluating therapeutic efficacy in clinical trials["@pet2023"][@tau2022].
Specificity: Binding affinity for target of interest
Blood-brain barrier penetration: Essential for CNS applications
Signal-to-noise: Clear distinction between target and background
PET Tracers for Neurodegeneration
Amyloid Imaging
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PET Imaging for Neurodegenerative Diseases
Introduction
Mermaid diagram (expand to render)
Positron Emission Tomography (PET) imaging is a powerful molecular imaging technique that enables visualization and quantification of pathological processes in the living brain. PET has become indispensable for diagnosing neurodegenerative diseases, tracking disease progression, and evaluating therapeutic efficacy in clinical trials["@pet2023"][@tau2022].
Clinical: Differentiating [PD](/diseases/parkinsons-disease) from other parkinsonisms
FP-CIT (DaTscan)
Target: Dopamine transporter
Status: FDA approved
Clinical: Differentiating essential tremor from [PD](/diseases/parkinsons-disease)
Raclopride
Target: D2 dopamine receptors
Use: Dopamine release studies
Alpha-Synuclein PET Tracers
Alpha-synuclein PET imaging represents one of the most significant unmet needs in neurodegenerative disease diagnostics. Unlike amyloid and tau PET, which have FDA-approved tracers, alpha-synuclein PET has historically lagged behind. At AD/PD 2026 in Copenhagen (March 17-21, 2026), researchers announced that a new generation of alpha-synuclein PET tracers has entered human testing — marking a major milestone for Parkinson's disease and synucleinopathy diagnostics.
Key Developments from AD/PD 2026
Human testing milestone: Multiple alpha-synuclein PET tracers presented early PET imaging studies in people with different synucleinopathies (Parkinson's disease, Dementia with Lewy Bodies, Multiple System Atrophy)
Target validation: Tracers designed to bind to alpha-synuclein aggregates in vivo, enabling visualization of Lewy body pathology
Differentiation potential: Early data suggests tracers may help distinguish between different synucleinopathies based on regional binding patterns
Tracer Development Landscape
| Company/Developer | Tracer | Stage | Notes | |------------------|--------|-------|-------| | MODAG | Novel α-syn PET tracer | Phase I | Presented at AD/PD 2026 | | Various academic groups | Multiple candidates | Phase I/II | Early human imaging studies | | Industry consortia | Next-gen tracers | Preclinical | Optimizing specificity |
Challenges for Alpha-Synuclein PET
Developing alpha-synuclein PET tracers is particularly challenging because:
Alpha-synuclein aggregates exist in multiple morphologies (fibrils, oligomers, membranes)
Non-specific binding to other proteins can confound signal
Lower abundance compared to amyloid plaques requires higher sensitivity
Species differences in tracer validation
Clinical Applications (Future)
Once validated, alpha-synuclein PET will enable:
Differential diagnosis: Distinguishing PD from other parkinsonisms (MSA, PSP)
DLB confirmation: Visualizing cortical Lewy body burden
Disease staging: Tracking alpha-synuclein spread through Braak stages in vivo
Clinical trials: Enrollment criteria and target engagement for alpha-synuclein therapies
Progression monitoring: Measuring pathological spread over time
Other Targets
Monoamine Oxidase B (MAO-B)
Target: MAO-B in astrocytes
Example: PBR111
Use: Neuroinflammation assessment
5-HT1A Receptors
Example: WAY-100635
Use: Serotonergic dysfunction in AD
Advantages
Quantitative: Provides numerical measures of pathology
Molecular specificity: Visualizes specific proteins/processes
Longitudinal tracking: Can monitor disease progression
Clinical trials: Enables biomarker-driven studies
Early detection: Can identify pathology before symptoms
Challenges
Radiopharmaceutical production: Requires cyclotron and chemistry expertise
Cost: Equipment and tracer production expensive
Radiation exposure: Limited repeat imaging
Partial volume effects: Small structures underestimated
Non-specific binding: Background signal can confound results
Biomarker validation: Some tracers lack proven clinical utility
Clinical Applications
Diagnosis
Differential diagnosis: Distinguishing between [dementia](/diseases/alzheimers-disease) types
Parkinsonism: Differentiating [PD](/diseases/parkinsons-disease) from [PSP](/diseases/progressive-supranuclear-palsy), [MSA](/diseases/multiple-system-atrophy)
| Target | Tracers | Stage | |--------|---------|-------| | Tau | Multiple | Phase II/III | | Synaptic density | UCB-J | Clinical | | Alpha-synuclein | Multiple | Phase I (human testing) | | TDP-43 | Early development | Preclinical |
March 2026 update: At AD/PD 2026, researchers announced that a new generation of alpha-synuclein PET tracers has entered human testing, marking a major milestone for synucleinopathy diagnostics.
Companies and Institutions
Radiopharmaceutical Companies
Avid Radiopharmaceuticals (Eli Lilly): Florbetapir, Flortaucipir
GE Healthcare: Various tracers
Siemens: Tracer development
PerkinElmer: Research tracers
Academic Centers
Washington University: PET tracer development
UCLA: Amyloid and tau imaging
University of Pennsylvania: Neuroinflammation imaging
Karolinska Institute: Dopamine imaging
Research Initiatives
Alzheimer's Disease Neuroimaging Initiative (ADNI): PET imaging protocols
Michael J. Fox Foundation: Parkinson's imaging biomarkers
Centres for Tau Program: Tau tracer validation
PET/CT and PET/MRI
PET/CT
Standard: Most common hybrid system
Advantages: CT provides anatomical reference
Limitations: Radiation from CT
PET/MRI
Emerging: Growing clinical adoption
Advantages: No additional radiation, better soft tissue
| Modality | Spatial Resolution | Molecular Info | Cost | Radiation | |----------|-------------------|----------------|------|-----------| | PET | 4-5 mm | High | High | High | | MRI | 1 mm | Medium | Medium | None | | CT | 1 mm | Low | Medium | Medium | | SPECT | 8-10 mm | Medium | Low | Medium |