In Vivo quantitative imaging of angiogenesis-targeted PFOB nanoparticles in a hypercholesterol rabbit model using 19F-MRI with ultra-short echo time balanced SSFP
Background aνb3-integrin targeted nanoparticle (NP) emulsions have been shown to detect and quantify angiogenesis and anti-angiogenic therapy in small animal models of atherosclerosis. While these NP were visualized in high resolution preand post-injection H-MRI via a Gadolinium (Gd) chelate, we seek to image the perfluoro-octyl bromide (PFOB) core directly via F MR. Early in vivo successes of F MR molecular imaging exploited the single resonance peak of perfluoro-crown-ether. However, PFOB, which is the more clinically-relevant NP with a better-understood human safety profile, has a more complex spectrum with seven F resonance peaks and multiple relaxation conditions, leading to chemical shift artifact and intra-voxel destructive interference. We hypothesize that a new technique—simultaneous dualfrequency F/H ultra-short echo time (UTE) balanced steady state free precession (b-SSFP) sequence with 3D radial readout—will allow efficient, sensitive imaging of the complex PFOB signal without the need for Gd and in sufficient resolution to discern the anatomy even in the presence of cardiac and respiratory motion.