Objective: To evaluate a fully automated image analysis pipeline to process vesicular monoamine transporters type 2 (VMAT2) [18F]AV-133 tracer positron emission tomography (PET) images, by comparison with a methodology requiring manual intervention.

Background: VMAT2 is a presynaptic protein that regulates package and release of dopamine and other monoamines into the synaptic vesicles. Nigrostriatal pathway integrity, measured with  [18F]AV-133 PET binding, is a useful diagnostic biomarker in Parkinson’s Disease (PD), where VMAT2 and [18F]AV-133 signal reduces with disease progression. Quantification of [18F]AV-133 PET typically requires manual placement of volumes of interest (VOIs), which is both subjective and time consuming. We present a fully automated methodology.

Method: 41 PET images (2 x 5min frames, mean 76.8 +/- 2.2min post injection) from 21 ‘idiopathic PD’ subjects, with associated T1-weighted (T1w) structural magnetic resonance images (MRI) were downloaded from the Parkinson’s Progression Markers initiative (PPMI) database (http://www.ppmi-info.org/data). PET frames were co-registered and aligned to the subject’s T1w-MRI. Six striatal regions of interest (ROIs) (left and right caudate, anterior putamen, and posterior putamen) were segmented from the T1w-MRI using multi-atlas- and convolution neural network (CNN)-based approaches. SUVRs were calculated using the occipital grey matter as the reference region, and compared via Pearson‘s coefficient to the PPMI’s published results.

Results: There were significant positive linear correlations between SUVR results for all six ROIs (r= 0.85 to 0.94, p<0.0001). Mean regression slope was 0.71 +/- 0.15, and mean intercept was 0.31 +/- 0.21. Exemplar segmentations [figure1] and correlation plots [figure2] are provided.

Conclusion: Our fully automated pipeline to quantify VMAT2 [18F]AV-133 PET images produced comparable results to that of a pipeline requiring manual intervention. This was despite the differences in the definition of reference region (inclusion of white matter versus grey-matter only) and target regions (spherical VOI versus whole region ROI) between our approach and that of PPMI. The proposed pipeline is robust and reproducible, therefore allowing for application in PD studies or other studies using nigrostriatal pathway integrity as a biomarker.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/automated-vmat2-18fav-133-pet-analysis-in-parkinsons-disease/