Abstract 13493: Optimized Ruptured Plaque Detection with Ytterbium Nanocolloids and Spectral CT

Abstract

Background: CT angiography and related techniques can rule out significant coronary disease, but localized detection of nonocclusive ruptured plaque is unreliable. Emerging development of x-ray K-edge molecular imaging (i.e., Spectral CT) can augment CTA by eliminating coronary calcium interference and identifying microthrombus within plaque microfissures.

Objective: In this research, Yb was synthesized into a novel Spectral CT nanoparticle and evaluated for SNR in suspension and targeted to fibrin.

Methods and Results: Organically soluble Yb(III) complexes were encapsulated at high density (>500K/nanoparticle) into a soft nanocolloid (YbNC) that is vascularly constrained within the imaging time frame. (~150nm). As proof of concept for K-edge detection, YbNC was imaged with a prototype Spectral CT scanner for blood pool contrast in rats. A strong ytterbium signal in the heart (false-colored red) was observed and is overlaid on a simultaneously-acquired conventional CT image (Fig. 1b). A polyacrylic phantom with CaCl₂ to mimic bones and clots with fibrin-antibody-targeted YbNC or control particles were imaged simultaneously with CT and Spectral CT. Clear signal for the bone mimics and targeted clots were observed with conventional CT, but only YBNC-targeted clots were detected with spectral CT (red overlay; p<0.05). Simulation modeling of expected K-edge contrast in humans using iodine, gold, ytterbium, and bismuth revealed the superiority of YB, even beyond gold, which is frequently reported by others.

Conclusions: A novel fibrin-specific YbNC offers optimal K-edge contrast potential for sensitive detection of microthrombus on ruptured plaque in humans.