X‐ray computed tomography (CT) imaging is one of the most widely used diagnostic imaging techniques in the clinic, and has raised significant interest in recent years both in research and practice owing to its many advantages such as deep penetration depth, high resolution and facile image processing. Developing heavy metal‐based CT contrast agents, especially heavy metal‐containing nanoparticulate CT contrast agents, has become a key focus in research fields to address issues of clinical iodinated agents involving short circulation time, low contrast efficiency and potential renal toxicity. In this review, we summarize the development of ytterbium (Yb)‐based CT contrast agents and highlight the design and applications of Yb‐based nanoparticulate CT contrast agents. Yb has high atomic number and higher abundance in the earth's crust relative to Au, Ta and Bi, which have received much attention as a CT contrast agents. In particular, in contrast to these metal elements, as well as I, Yb has K‐edge energy that is located just within the higher‐intensity region of X‐ray spectra, which can induce significant enhancement in the contrast efficiency. When encapsulated in nanoparticles, Yb can remain in the circulation for a long time. This long in vivo circulation time, combined with the proper K‐edge energy and a large absorption cross‐section of Yb in the near‐infrared region, makes Yb‐based nanoparticles particularly promising in angiography, ‘multicolor’ spectral CT imaging, and multimodal imaging. Finally, we also discuss the prospects and the challenges in the development of Yb‐based CT contrast agents. Copyright © 2014 John Wiley & Sons, Ltd.

In vivo upconversion luminescence (UCL) imaging, exhibiting favorable characteristics such as high photostability, no blinking, sharp emission lines, and long lifetimes, is recognized as the excellent and significant photoluminescence imaging for the future. To develop the imaging system with high visual sensitivity and tissue penetration, the functional molecules with X-ray computed tomography (CT) contrast were grafted onto upconversion nanoparticles to obtain β-NaYF₄:18% Yb³⁺,2%Er³⁺@SiO₂-I/PEG (UCNPs@SiO₂-I/PEG) nanoprobes. These nanoprobes are water-soluble, have low cytotoxicity, and possess excellent UCL and remarkable CT contrast. Of particular note is that, besides the element iodine, rare earth elements (Y, Yb, and Er) present in the nanoprobes also show CT contrast. Moreover, no background autofluorescence signal is found in in vivoUCL images. We believe that these nanoprobes with dual modal in vivo imaging of UCL and CT can serve as a promising platform for clinical diagnosis or biomedical studies.

We demonstrate a novel noncovalent method for producing Gd^III-functionalized gold nanorods as multimodal contrast agents for MRI and CT imaging. The ligand is connected to the surface of the gold nanorods by a noncovalent bond making the Gd^III ions directly accessible to water molecules, and resulting in a longitudinal relaxivity as high as 21.3 mM⁻¹ s⁻¹. In addition, compared with spherical gold nanoparticles, gold nanorods have more binding sites for Gd^III ions due to their large surface-to-volume ratio. Benefiting from the advantages of the new type of carry material and the novel fabrication approach, the multimodal imaging probes exhibit a high longitudinal relaxivity r₁ on the order of 1.1 × 10⁷ mM⁻¹ s⁻¹ on a per-particle basis, which is 24 times higher than that of Gd^III-ion-functionalized spherical gold nanoparticles. Furthermore, CT imaging shows that such nanoprobes could induce an efficient contrast enhancement when the gold concentration is at least equal to 1.31 mg ml⁻¹. These results demonstrate that the as-prepared Gd functinalized gold nanorods could provide a new and versatile platform for the development of multimodal imaging probes.

Primary pericardial malignant mesothelioma is an extremely rare neoplasm that arises from the pericardial mesothelial cell layers. Clinical symptoms and signs are frequently nonspecific, and the diagnosis is usually made after surgery or at autopsy. There is no standard treatment for pericardial mesothelioma; nonetheless, radical surgery is the mainstay of therapy for localized disease. The neoplasm is highly aggressive and carries a dismal prognosis with an overall survival of less than six months. This paper presents a case study of a 68-year-old patient with a primary pericardial malignant mesothelioma. Radiologic evaluation revealed a small nodule in the posterior pericardium with pericardial and bilateral pleural effusions. The diagnosis was established after surgery by histological and immunohistochemical studies. The patient remained alive and free of disease for about 24 months; however, due to rapid local recurrence, the patient died 27 months after the surgical treatment.

We report the facile and scalable synthesis of a highly monodispersed inorganic nanostructure based on well-designed Gd(OH)₃ nanorods. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as energy-dispersive spectroscopy (EDS) were applied to characterize the samples, indicating that the nanomaterials with an average length of 100 nm and an average diameter of 15 nm showed a typical hexagonal phase. Biocompatibility tests were performed from in vitro cell experiments to in vivo long-term histological assessment, indicating that the Gd(OH)₃ nanorods were promising for further bio-related application. Owing to the excellent paramagnetic behavior, we further investigated the capability of the nanorods as MRI contrast agent. Compared with the conventional Gd–DTPA complex, the well-designed Gd(OH)₃ nanorods present a higher T₁ relaxation rate, showing more potential for biomedicine applications.