MMP9 and atherosclerosis: In 2009, Rudd et al. found that in atherosclerosis patients and high-risk subjects, serum MMP-3 levels were associated with 18F-FDG uptake, measured by the TBR of 18F-FDG PET, in the descending aorta, while MMP-9 levels were associated with carotid TBR [144].