Various Positron Emission Tomography (PET) studies using radiotracers that measure these proteins in the brain, including [11C]-Pittsburgh Compound B (PiB), [18F]-Florbetaben (FBB), or [18F]-florbetapir ([18F]-AV-45), revealed significant increased retention and standardized uptake value ratios (SUVR) in PD APOE4 carriers than non-carriers (See Table 1 for more details) (Maetzler et al., 2009; Gomperts et al., 2012; Vijayaraghavan et al., 2014; Akhtar et al., 2017; Jung et al., 2021). This evidence concerns the gene APOE and Parkinson disease.