Correlation of sequential nuclear imaging with interval histological changes in a porcine abdominal aortic aneurysm model

Abstract

The mechanism of abdominal aortic aneurysm (AAA) formation remains incompletely described. AAA were created in the infrarenal aortas of 14 Yorkshire swine (25–35kg) using balloon dilation and luminal collagenase (8000u) and elastase (500u) perfusion. Positron emission tomography computed tomography (PET CT) was performed on post-operative days 1, 3, 7, 14, and 28 in 5 swine. Cellular uptake of 18-fluorodeoxyglucose (FDG) was quantified within AAA and sham segments of aorta using radioactive decay density within an ellipsoid volume of interest (VOI). Nine swine were euthanized at 1(n=3), 3(n=1), 7(n=1), 14(n=1), 21(n=2) and 28(n=1) days for histological analysis (H&E, Masson’s trichrome, and Verhoeff-van Giesen stain). AAA activity on day 7 (32.7%±22.3%) was significantly higher (p=0.01) than day one (−2.8±17.9%) and day 28 (1.2±22.9%). Inflammatory response, smooth muscle cell regeneration, and the appearance of hyaline matrix deposition correlate to interval FDG activity of the AAA. Extensive elastin fiber disruption was evident at all time points. FDG uptake demonstrates increased local metabolic demand following mechanical and enzyme-induced AAA formation. Regression of relative FDG uptake at 28 days suggests that elastase induced injury may not be perpetual. PET CT may provide a useful method for longitudinal noninvasive measurements within a single animal for endovascular research. Change in Relative Activity Within Ellipsoid VOIs Enclosing Porcine AAA and Sham Aorta