Imaging aspirin effect on macrophages in the wall of human cerebral aneurysms using ferumoxytol-enhanced MRI: preliminary results

Abstract

Background and purpose: Daily intake of aspirin was shown to decrease human cerebral aneurysm rupture by 60%. The feasibility of imaging macrophages in human cerebral aneurysm walls using ferumoxytol-enhanced MRI has been demonstrated. The goal of the present study is to image aspirin effect on macrophages in the wall of human cerebral aneurysm using ferumoxytol-enhanced MRI.

Material and methods: Five patients with known intracranial aneurysms underwent baseline imaging using T2(*) gradient-echo and T1 MRI sequences using ferumoxytol-enhanced MRI 72-hour post-ferumoxytol infusion. Patients then received 81 mg aspirin per os daily. After 3 months, imaging studies were repeated and analyzed by co-registration using a histogram and subtraction of follow-up images from baseline.

Results: In all five patients, after 3 months of treatment with aspirin, the signal intensity corresponding to the uptake of ferumoxytol by macrophages in the aneurysm wall was less intense than in the baseline images. This was confirmed by co-registration of images using histogram and subtraction of follow-up images from baseline.

Conclusion: These preliminary results suggest the feasibility of imaging aspirin effect on macrophages localized in the wall of human cerebral aneurysm using ferumoxytol-enhanced MRI. The findings provide radiographic evidence of decreased inflammation in human cerebral aneurysms with daily intake of aspirin using macrophages as a surrogate marker for inflammation.

Keywords: Aneurysm; Aspirin; COX-2; Cyclooxygenase-2; Ferumoxytol; Inflammation; MRI; Macrophages; Magnetic resonance imaging; Microsomal prostaglandin E(2) Synthase-1; USPIO; Ultra-supra-magnetic iron oxide nanoparticles; mPGES-1.