Early-Frame PET Acquisition May Provide Mechanism for Determining Alzheimer’s Disease Progression

alt text goes hereImaging with positron emission tomography (PET) has become an important part of diagnosing neurodegenerative diseases.  PET scans provide important information about specific regions of the brain or about robustness of perfusion – how well blood is being circulated to where it should go. Several biomarkers exist that act to specifically target potential neuronal dysfunction such as amyloid β (Aββ plaques, tau tangle accumulation, or measurements of glucose metabolism in the brain. The tracers used are radioligands – radioactive analogs of compounds – that are injected, monitored for retention, and detected over time as they perfuse throughout the brain. Individuals with Alzheimer’s Disease (AD) typically show an increase in Aβ and tau accumulation, and a decrease in glucose metabolism as the disease progresses. Because neuronal dysfunction of AD can originate decades before clinical symptoms appear, researchers are focusing on early detection; however, multiple PET scans using various radioligands are expensive and invasive. 

Duygu Tosun-Turgut and Alison Myoraku, along with their co-authors from Roche and UC Berkeley, investigated whether the information collected from early frames of an Aβ PET scan using 18F-Florbetapir (which measures Aβ) is comparable to that of an FDG PET scan using 18F-FDG (which measures glucose metabolism). FDG-PET scans act as a ground truth measurement for AD pathology. They also tested whether the A radioligand might provide the same information as the FDG PET scan data. Early-frame 18F-Florbetapir scans were compared with 18F-FDG PET scans from 100 cognitively diverse individuals with varying levels of AD cognitive impairment states: cognitively unimpaired (CU), mild cognitive impairment (MCI), and Dementia. By focusing on 84 different regions of cerebral interest, they analyzed whether early-frame images could capture the same information as an FDG scan, and the answer was “yes”.

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They found moderate to strong correlations across all regions of interest and disease states, showing that these regional standardized uptake value ratios (SUVRs) do not significantly differ. In a separate analysis, they compared SUVRs from early-frame scans using 18F-Florbetapir with 18F-FDG PET and found strong correlation as well. This study is clinically significant because 18F-Florbetapir and 18F-fluorbetaben tracers can be used interchangeably for PET scans and early frames can act as an early diagnostic measure in patients that span the AD continuum without affecting clinical options.

This paper was published in The European Journal of Hybrid Imaging. Additional authors include Gregory Klein (Roche) and Susan Landau (UC Berkeley).