Evaluation of a Novel Tantalum Oxide-Based Contrast Agent for Liver Imaging and Tumor Detection in Dual-Energy CT: A Preclinical Proof-of-Concept Study.

Rationale And Objectives: To evaluate an experimental intravascular carboxybetaine zwitterionic tantalum oxide (TaCZ) nanoparticle CT contrast agent versus iopamidol for hepatic imaging and tumor detection using a multiphase dual-layer spectral CT (DLCT).

Materials And Methods: Rabbits with small (0.6 - 0.

Insights into nanoparticle surface bonding and coating architecture via multinuclear NMR.

Tantalum oxide nanoparticles (TaO NPs) are promising as high--contrast agents for computed tomography (CT) due to their profound imaging benefits relative to those of clinical iodinated contrast media (ICM) at the X-ray tube voltages ≥100 kVp required for most patients. Furthermore, TaO NPs have prevailed through extensive non-GLP and GLP (good laboratory practice) preclinical development, including in vivo/vitro safety testing and imaging efficacy studies. This is due in part to innovative structural engineering of the NPs' core size and coating, which has been shown to provide favorable pharmacokinetics and promote rapid renal clearance, with negligible organ retention.

Performance of an Intravascular Tantalum Oxide-Based Nanoparticle Computed Tomography Contrast Agent in Preclinical Hepatic Tumor Detection.

Background: Noniodinated intravenous contrast agents have shown significant potential to improve computed tomography (CT) imaging; however, in vivo evidence for impact on lesion detection remains scarce.

Purpose: The aim of the study was to compare a novel intravenous carboxybetaine zwitterionic-coated tantalum oxide (TaCZ) nanoparticle contrast agent to clinical iodinated contrast agent for the detection of liver tumors in a rabbit tumor model at CT.

Methods: Following hepatic implantation of VX2 tumors, n = 10 rabbits were repeatedly scanned on a clinical CT system before and at 40, 105, and 180 seconds after intravenous contrast injection of 540 mg element (Ta or I) per kilogram of body weight using TaCZ or iopamidol.

Novel intravascular tantalum oxide-based contrast agent achieves improved vascular contrast enhancement and conspicuity compared to Iopamidol in an animal multiphase CT protocol.

Background: To assess thoracic vascular computed tomography (CT) contrast enhancement of a novel intravenous tantalum oxide nanoparticle contrast agent (carboxybetaine zwitterionic tantalum oxide, TaCZ) compared to a conventional iodinated contrast agent (Iopamidol) in a rabbit multiphase protocol.

Methods: Five rabbits were scanned inside a human-torso-sized encasement on a clinical CT system at various scan delays after intravenous injection of 540 mg element (Ta or I) per kg of bodyweight of TaCZ or Iopamidol. Net contrast enhancement of various arteries and veins, as well as image noise, were measured.

1-Methyl-3-(naphthalen-2-yl)cyclo-penta-diene.

The title compound, CH, an asymmetric naphthyl-/methyl-substituted cyclo-penta-diene was synthesized and one isomer of five accessible through sigmatropic rearrangement was isolated and characterized by H NMR and X-ray diffraction. The crystal packing features an inter-molecular C-H⋯π inter-action.

Oral CT Contrast Agents: What's New and Why, From the Special Series on Contrast Media.

Current CT oral contrast agents improve the conspicuity of and confidence in bowel and peritoneal findings in many clinical scenarios, particularly for outpatient and oncologic abdominopelvic imaging. Yet, existing positive and neutral oral contrast agents may diminish the detectability of certain radiologic findings, frequently in the same scans in which the oral contrast agent improves the detectability of other findings. With ongoing improvements in CT technology, particularly multienergy CT, opportunities are opening for new types of oral contrast agents to further improve anatomic delineation and disease detection using CT.

Synthesis, crystal structure, EPR, and DFT studies of an unusually distorted vanadium(II) complex.

We report the synthesis and structure of the most highly distorted four-coordinate d ion known to date that also serves as the second known example of a bis(biphenolato) transition metal complex. We demonstrate the application of density functional theory to calculate the magnetic parameters derived from the experimental and simulated EPR spectra.

An Intravascular Tantalum Oxide-based CT Contrast Agent: Preclinical Evaluation Emulating Overweight and Obese Patient Size.

Purpose To compare the CT imaging performance of a carboxybetaine zwitterionic-coated tantalum oxide (TaCZ) nanoparticle CT contrast agent with that of a conventional iodinated contrast agent in a swine model meant to simulate overweight and obese patients. Materials and Methods Four swine were evaluated inside three different-sized adipose-equivalent encasements emulating abdominal girths of 102, 119, and 137 cm. Imaging was performed with a 64-detector row CT scanner at six scan delays after intravenous injection of 240 mg element (Ta or I) per kilogram of body weight of TaCZ or iopromide.

Liquid tissue surrogates for X-ray and CT phantom studies.

Purpose: To develop a simple method for producing liquid-tissue-surrogate (LTS) materials that accurately represent human soft tissues in terms of density and X-ray attenuation coefficient.

Methods And Materials: We evaluated hypothetical mixtures of water, glycerol, butanol, methanol, sodium chloride, and potassium nitrate; these mixtures were intended to emulate human adipose, blood, brain, kidney, liver, muscle, pancreas, and skin. We compared the hypothetical densities, effective atomic numbers (Z ), and calculated discrete-energy CT attenuation [Hounsfield Units (HU)] of the proposed materials with those of human tissue elemental composition as specified in International Commission on Radiation Units (ICRU) Report 46.

The Effect of Patient Diameter on the Dual-Energy Ratio of Selected Contrast-Producing Elements.

Objectives: The aim of this study was to assess whether the low- to high-kVp computed tomography (CT) number ratio at dual-energy CT is affected by changes in patient diameter.

Methods: Seven contrast-producing elements were housed sequentially within an abdomen phantom. Fat rings enlarged the phantom diameter from 26 to 44 cm.

Opportunities for new CT contrast agents to maximize the diagnostic potential of emerging spectral CT technologies.

The introduction of spectral CT imaging in the form of fast clinical dual-energy CT enabled contrast material to be differentiated from other radiodense materials, improved lesion detection in contrast-enhanced scans, and changed the way that existing iodine and barium contrast materials are used in clinical practice. More profoundly, spectral CT can differentiate between individual contrast materials that have different reporter elements such that high-resolution CT imaging of multiple contrast agents can be obtained in a single pass of the CT scanner. These spectral CT capabilities would be even more impactful with the development of contrast materials designed to complement the existing clinical iodine- and barium-based agents.

A Proposed Computed Tomography Contrast Agent Using Carboxybetaine Zwitterionic Tantalum Oxide Nanoparticles: Imaging, Biological, and Physicochemical Performance.

Objectives: The aim of this study was to produce and evaluate a proposed computed tomography (CT) contrast agent based on carboxybetaine zwitterionic (CZ)-coated soluble tantalum oxide (TaO) nanoparticles (NPs). We chose tantalum to provide superior imaging performance compared with current iodine-based clinical CT contrast agents. We developed the CZ coating to provide biological and physical performance similar to that of current iodinated contrast agents.

CT Image Contrast of High-Z Elements: Phantom Imaging Studies and Clinical Implications.

Purpose: To quantify the computed tomographic (CT) image contrast produced by potentially useful contrast material elements in clinically relevant imaging conditions.

Materials And Methods: Equal mass concentrations (grams of active element per milliliter of solution) of seven radiodense elements, including iodine, barium, gadolinium, tantalum, ytterbium, gold, and bismuth, were formulated as compounds in aqueous solutions. The compounds were chosen such that the active element dominated the x-ray attenuation of the solution.

Reversible catalytic dehydrogenation of alcohols for energy storage.

Reversibility of a dehydrogenation/hydrogenation catalytic reaction has been an elusive target for homogeneous catalysis. In this report, reversible acceptorless dehydrogenation of secondary alcohols and diols on iron pincer complexes and reversible oxidative dehydrogenation of primary alcohols/reduction of aldehydes with separate transfer of protons and electrons on iridium complexes are shown. This reactivity suggests a strategy for the development of reversible fuel cell electrocatalysts for partial oxidation (dehydrogenation) of hydroxyl-containing fuels.

Highly selective electrocatalytic dehydrogenation at low applied potential catalyzed by an Ir organometallic complex.

A homogeneous organometallic Ir complex was shown to catalyze the electro-oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde at a very low applied potential with remarkably high selectivity and Faradaic efficiency. In the chemical catalysis, when stoichiometric oxidant and anionic base were used to separately accept electrons and protons, aldehyde selectivity was in agreement with electrolysis results.

Biological performance of a size-fractionated core-shell tantalum oxide nanoparticle x-ray contrast agent.

Objectives: Metal-containing nanoparticles show great promise as x-ray contrast media and could enable reduced radiation dose, increased contrast, and the visualization of smaller anatomic features. In this study, we report progress toward these goals using a size-fractionated core-shell tantalum oxide nanoparticle contrast agent.

Materials And Methods: A core-shell tantalum oxide nanoparticle contrast agent was synthesized and size fractionated for preclinical investigation of biodistribution, blood half-life, organ retention, and histopathology.

Preclinical assessment of a zwitterionic tantalum oxide nanoparticle X-ray contrast agent.

Tantalum oxide nanoparticles show great potential as the next generation of X-ray contrast media. Recently, we reported advances in tantalum oxide nanoparticles and identified improvements that were required for such particles to progress further. Namely, the viscosity of concentrated particles, the amount of retention in reticuloendothelial (RES) tissues, and the effect of large quantities of particles on the kidneys after administration were all identified as critical factors which needed further study, understanding, and development.

Synthesis, characterization, and computed tomography imaging of a tantalum oxide nanoparticle imaging agent.

Water-soluble ≤6 nm tantalum oxide nanoparticles have been synthesized and characterized in solution using HPLC-ICP, DLS, and multinuclear NMR. Nanoparticle formulation permitted intravenous injection, in vivo imaging, and subsequent renal clearance. A clinical CT scanner provided excellent resolution following agent injection, and distribution to the arterial system was visualized.