An Early Investigation of Ytterbium Nanocolloids for Selective and Quantitative 'Multicolor' Spectral CT Imaging

We report a novel molecular imaging agent based on Ytterbium (Yb) designed for use with Spectral “multi-color” Computed Tomogrphy (CT). Spectral CT or multi-ycolored CT provides all of the benefits of traditional CT, i.e., rapid tomographic X-ray imaging, but in addition, it simultaneously discriminates metal-rich contrast agents based on the elements unique x-ray K-edge energy signature. Our synthetic approach involved the use of organically soluble Yb(III)-complex to produce nanocolloids of Yb of noncrystalline nature incorporating high density of Yb (>500K/nanoparticle) into a stable metal particle. The resultant particles are constrained to vasculature (~200nm) and are highly selective for binding fibrin in the ruptured atherosclerotic plaque. Nanoparticles exhibited excellent signal sensitivity and the spectral CT technique uniquely discriminates the k-edge signal (60keV) of Yb from calcium (bones). Bio-elimination and preliminary bio-distribution studied reflected the overall safety and defined clearance of these particles in a rodent model.