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Updated: Nov 10, 2025
Full- versus Sub-Regional Quantification of Amyloid-Beta Load on Mouse Brain Sections
Published on: May 19, 2022
AMYQ: An index to standardize quantitative amyloid load across PET tracers
Jordi Pegueroles1,2, Victor Montal1,2, Alexandre Bejanin1,2
1Sant Pau Memory Unit, Department of Neurology, Hospital de la Santa Creu i Sant Pau, Biomedical Research Institute Sant Pau, Universitat Autònoma de Barcelona, Barcelona, Spain.
Introduction:
Positron emission tomography (PET) amyloid quantification methods require magnetic resonance imaging (MRI) for spatial registration and a priori reference region to scale the images. Furthermore, different tracers have distinct thresholds for positivity. We propose the AMYQ index, a new measure of amyloid burden, to overcome these limitations.
Methods:
We selected 18F-amyloid scans from ADNI and Australian Imaging, Biomarker & Lifestyle Flagship Study of Ageing (AIBL) with the corresponding T1-MRI. A subset also had neuropathological data. PET images were normalized, and the AMYQ was calculated based on an adaptive template. We compared AMYQ with the Centiloid scale on clinical and neuropathological diagnostic performance.
Results:
AMYQ was related with amyloid neuropathological burden and had excellent diagnostic performance to discriminate controls from patients with Alzheimer's disease (AD) (area under the curve [AUC] = 0.86). AMYQ had a high agreement with the Centiloid scale (intraclass correlation coefficient [ICC] = 0.88) and AUC between 0.94 and 0.99 to discriminate PET positivity when using different Centiloid cutoffs.
Discussion:
AMYQ is a new MRI-independent index for standardizing and quantifying amyloid load across tracers.
Insights
The new AMYQ index quantifies amyloid burden using PET scans without MRI, showing high accuracy in diagnosing Alzheimer's disease and strong agreement with existing scales.
Area of Science:
- Neuroimaging
- Biomarkers
- Alzheimer's Disease Research
Background:
- Current positron emission tomography (PET) amyloid quantification relies on magnetic resonance imaging (MRI) and reference regions.
- Different amyloid tracers have varying positivity thresholds, complicating standardized measurements.
Purpose of the Study:
- To introduce the AMYQ index, a novel measure for amyloid burden.
- To overcome limitations of existing PET amyloid quantification methods, including MRI independence and tracer variability.
Main Methods:
- Utilized 18F-amyloid PET scans and T1-MRI from ADNI and AIBL cohorts.
- Calculated the AMYQ index using normalized PET images and an adaptive template.
- Compared AMYQ performance against the Centiloid scale using clinical and neuropathological data.
Main Results:
- AMYQ demonstrated excellent diagnostic performance for Alzheimer's disease (AD) detection (AUC = 0.86).
- AMYQ showed high agreement with the Centiloid scale (ICC = 0.88).
- AMYQ achieved high AUCs (0.94-0.99) for discriminating PET positivity across different Centiloid cutoffs.
Conclusions:
- The AMYQ index provides an MRI-independent method for standardizing amyloid load quantification.
- AMYQ offers a reliable and accurate measure of amyloid burden across different PET tracers.
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