Combined PET/DCE-MRI in a Rabbit Model of Atherosclerosis: Integrated Quantification of Plaque Inflammation, Permeability, and Burden During Treatment With a Leukotriene A4 Hydrolase Inhibitor

OBJECTIVES

The authors sought to develop combined positron emission tomography (PET) dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) to quantify plaque inflammation, permeability, and burden to evaluate the efficacy of a leukotriene A4 hydrolase (LTA4H) inhibitor in a rabbit model of atherosclerosis.

BACKGROUND

Multimodality PET/MRI allows combining the quantification of atherosclerotic plaque inflammation, neovascularization, permeability, and burden by combined ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET, DCE-MRI, and morphological MRI. The authors describe a novel, integrated PET-DCE/MRI protocol to noninvasively quantify these parameters in aortic plaques of a rabbit model of atherosclerosis. As proof-of-concept, the authors apply this protocol to assess the efficacy of the novel LTA4H inhibitor BI691751.

METHODS

New Zealand White male rabbits (N = 49) were imaged with integrated PET-DCE/MRI after atherosclerosis induction and 1 and 3 months after randomization into 3 groups: 1) placebo; 2) high-dose BI691751; and 3) low-dose BI691751. All animals were euthanized at the end of the study.

RESULTS

Among the several metrics that were quantified, only maximum standardized uptake value and target-to-background ratio by ¹⁸F-FDG PET showed a modest, but significant, reduction in plaque inflammation in rabbits treated with low-dose BI691751 (p = 0.03), whereas no difference was detected in the high-fat diet and in the high-dose BI691751 groups. No differences in vessel wall area by MRI and area under the curve by DCE-MRI were detected in any of the groups. No differences in neovessel and macrophage density were found at the end of study among groups.

CONCLUSIONS

The authors present a comprehensive, integrated ¹⁸F-FDG PET and DCE-MRI imaging protocol to noninvasively quantify plaque inflammation, neovasculature, permeability, and burden in a rabbit model of atherosclerosis on a simultaneous PET/MRI scanner. A modest reduction was found in plaque inflammation by ¹⁸F-FDG PET in the group treated with a low dose of the LTA4H inhibitor BI691751.