Abstract 2237: Rapid T1w Molecular Imaging of Atherosclerotic Angiogenesis with Colloidal Iron Oxide Nanoparticle

Introduction : MR molecular imaging and anti-angiogenic treatment with integrin-targeted nanoparticles offer an attractive nanomedicine tool against atherosclerosis. Objective: The objective was to synthesize targeted colloidal iron oxide nanoparticles (CION), which allow high-resolution T1 w images within 2hrs of injection without T2* artifacts or latent blood pool interference. Method: Oleate-coated magnetite nanoparticles were suspended in vegetable oil and emulsified with phospholipid surfactants. With MR (1.5T & 3T), CION (140 –160 nm) were characterized in solution, on fibrin clot phantoms and targeted to angiogenesis in vivo . Blood pool signal was measured over time following IV injection of CION. Result: CION r1 ionic and particulate relaxivities were 1.1±0.1 mmol[Fe] −1 s −1 and 18466±1739 mmol[CION] −1 s −1 at 1.5T and 0.7±0.06 mmol[Fe] −1 s −1 and 10966±1062 mmol[CION] −1 s −1 at 3T. CION targeted to fibrin clots produced marked T1w signal enhancement (SNR=26) versus control clots (SNR=10). T2-weighted images of the bound agent was notable for signal dropout. In atherosclerotic rabbits, the T1 & T2* effects on blood signal ( i.e. , background interference) were resolved in < 1hr. In vivo T1w molecular imaging of the atherosclerotic neovasculature 2h post-injection, was analyzed with a semiautomatic algorithm and demonstrated the potential of T1w neovascular imaging. Conclusion: Targeted CION are a new class of vascular constrained T1w molecular imaging agent with potential for detection and characterization of ruptured plaque and atherosclerotic neovasculature, which overcome the temporal and spatial imaging challenges of previous iron oxide agents.