Predicting Abdominal Aortic Aneurysm Progression: The Role of 18F-Fluorodeoxyglucose Aortic Wall Uptake and Flow Dynamics

Abstract

As abdominal aortic aneurysms (AAA) rupture results in a high mortality rate, early detection and risk stratification are critical for timely elective intervention. Although the maximum diameter is the sole imaging metric used to assess risk, other factors may provide complementary information. This study investigated the role of inflammation and hemodynamics in AAA progression. Methods: Patients with AAA underwent hybrid 18F-fluorodeoxyglucose ([18F]FDG) PET/CMR imaging, including a four-dimensional flow sequence and contrast-enhanced magnetic resonance angiography, and were followed to assess AAA diameter growth rate. Abdominal aorta hemodynamics and [18F]FDG PET target-to-background (TBR) were quantified at 28 standardized regions. Correlations between AAA diameter, hemodynamics, PET and growth rate were assessed. Results: Thirty-two AAA patients (84.4% men) with a median age of 73 and an interquartile range of [68; 77] years were prospectively recruited. The AAA maximum diameter was 48.1 [44.8; 55.0] mm, and the growth rate was 2.7 [1.3; 4.0] mm/year during a follow-up of 2 [1.1; 3.5] years. The AAA maximum diameter (R = 0.443, p = 0.011) and flow vorticity (R = 0.453, p = 0.009) showed significant bivariate correlation with the growth rate. When correcting for the aneurysm diameter, the helicity density was significantly correlated with the growth rate (p = 0.045), while the AAA thrombus volume was inversely associated with it (p = 0.042). Aneurysms with negative helicity density (counterclockwise rotation) grew significantly faster (p = 0.042) than those with positive helicity. In multivariable analysis, beyond the AAA diameter, the thrombus volume, helicity density and TBR were inversely related to the growth rate. Conclusions: Integrating flow, inflammatory and thrombus information may improve AAA growth rate prediction beyond the maximum aneurysm diameter.