Background-Molecular imaging of thrombus within fissures of vulnerable atherosclerotic plaques requires sensitive detection of a robust thrombus-specific contrast agent. In this study, we report the development and characterization of a novel ligand-targeted paramagnetic molecular imaging agent with high avidity for fibrin and the potential to sensitively detect active vulnerable plaques. Methods and Results-The nanoparticles were formulated with 2.5 to 50 mol% Gd-DTPA-BOA, which corresponds to Ͼ50 000 Gd 3ϩ atoms/particle. Paramagnetic nanoparticles were characterized in vitro and evaluated in vivo. In contradistinction to traditional blood-pool agents, T1 relaxation rate as a function of paramagnetic nanoparticle number was increased monotonically with Gd-DTPA concentration from 0.18 mL ⅐ s Ϫ1 · pmol Ϫ1 (10% Gd-DTPA nanoparticles) to 0.54 mL ⅐ s Ϫ1 · pmol Ϫ1 for the 40 mol% Gd-DTPA formulations. Fibrin clots targeted in vitro with paramagnetic nanoparticles presented a highly detectable, homogeneous T1-weighted contrast enhancement that improved with increasing gadolinium level (0, 2.5, and 20 mol% Gd). Higher-resolution scans and scanning electron microscopy revealed that the nanoparticles were present as a thin layer over the clot surface. In vivo contrast enhancement under open-circulation conditions was assessed in dogs. The contrast-to-noise ratio between the targeted clot (20 mol% Gd-DTPA nanoparticles) and blood was Ϸ118Ϯ21, and that between the targeted clot and the control clot was 131Ϯ37. Conclusions-These

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Magnetic resonance (MR) diffusion measurements of the abdomen were performed in 12 healthy volunteers by using a diffusion-weighted single-shot sequence both without and with pulse triggering for different trigger delays. Pulse triggering to the diastolic heart phase led to reduced motion artifacts on the diffusion-weighted MR images and to significantly improved accuracy and reproducibility of measurements of the apparent diffusion coefficients, or ADCs, of abdominal organs.

Quantification of the lambda in vivo allows differentiation between normal and acutely or chronically infarcted myocardium, with high sensitivity and specificity.

In addition to the information traditionally provided with reconstructed perfusion parameter maps, 3D susceptibility-based perfusion MR images allow the identification of acute MCA thromboembolism with a sensitivity higher than that of CT.