CT phantom images of (A) Hf-UiO, (B) Zr-UiO, and (C) Iodixanol dispersed in water. From the top, counterclockwise, the slots have [Hf/Zr/I] = 0, 0.05, 0.10, 0.15, and 0.20 M. (D) X-ray attenuation as a function of [Hf/Zr/I] for Hf-UiO, Zr-UiO, and Iodixanol at 50 kVp. (E) Attenuation coefficient vs. photon energy for Hf, Zr, and I.