CT Image Contrast of High-<i>Z</i>Elements: Phantom Imaging Studies and Clinical Implications

Fitzgerald, Peter; Colborn, Robert E.; Edic, Peter M.; Lambert, Jack W.; Torres, Andrew S.; Bonitatibus, Peter J.; Yeh, Benjamin M.

doi:10.1148/radiol.2015150577

Cited by 78 publications

(78 citation statements)

References 38 publications

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“…23,32 Other high-Z elements with potential as possible CT contrast agents include gold, 33,34 ytterbium, 35 and gadolinium. 36 In the interest of simplicity, these elements were not considered in the current study; but based on our consistent findings for the high-Z elements we tested and the increased image contrast compared to iodine at higher energies for other high-Z elements, 19 one would expect that they, too, would exhibit the characteristic of contrast retention at high-keV levels compared to iodine in VMS images at higher energy levels.…”

Section: Discussionmentioning

confidence: 83%

“…The main aim of this study was to compare the contrast profiles of the different elements, and as such, a detailed analysis of the composition and concentration was not a priority and has been performed rigorously elsewhere. 19 Fourth, the semisolid nature of the fat encasements did not allow for perfect repeatability between different setups, so the precision of those datasets is likely to be lower than for the initial 203-mm diameter phantom configuration. Fifth, a control phantom without artifact-producing metal implants was not imaged.…”

Section: Discussionmentioning

confidence: 99%

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Complementary contrast media for metal artifact reduction in dual-energy computed tomography

et al. 2015

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Abstract. Metal artifacts have been a problem associated with computed tomography (CT) since its introduction. Recent techniques to mitigate this problem have included utilization of high-energy (keV) virtual monochromatic spectral (VMS) images, produced via dual-energy CT (DECT). A problem with these high-keV images is that contrast enhancement provided by all commercially available contrast media is severely reduced. Contrast agents based on higher atomic number elements can maintain contrast at the higher energy levels where artifacts are reduced. This study evaluated three such candidate elements: bismuth, tantalum, and tungsten, as well as two conventional contrast elements: iodine and barium. A water-based phantom with vials containing these five elements in solution, as well as different artifact-producing metal structures, was scanned with a DECT scanner capable of rapid operating voltage switching. In the VMS datasets, substantial reductions in the contrast were observed for iodine and barium, which suffered from contrast reductions of 97% and 91%, respectively, at 140 versus 40 keV. In comparison under the same conditions, the candidate agents demonstrated contrast enhancement reductions of only 20%, 29%, and 32% for tungsten, tantalum, and bismuth, respectively. At 140 versus 40 keV, metal artifact severity was reduced by 57% to 85% depending on the phantom configuration.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Complementary contrast media for metal artifact reduction in dual-energy computed tomography

et al. 2015

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“…16,17 However, these results were obtained using large, dense phantoms that represent the abdomen of an overweight-to-obese adult. The effect of these phantoms is to “harden” the X-ray spectrum, increasing the mean energy of the spectrum.…”

Section: Discussionmentioning

confidence: 99%

“…We have found that the specific design of the zwitterionic ligand can affect the osmolality, viscosity, and renal clearance of the nanoparticles; we hypothesized that a design could be found that allows the nanoparticle to satisfy all physicochemical and biological safety requirements. Furthermore, a recent report 16 suggests that tantalum is the most promising candidate among the chemical elements evaluated for use in general-purpose CT contrast agents in terms of toxicity, cost, and availability. In addition, other work 17 predicts up to 65% improvement in CT image contrast for large-to-obese patients when tantalum-based rather than iodinated contrast agents are given at equal mass concentration.…”

Section: Introductionmentioning

confidence: 99%

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A Proposed Computed Tomography Contrast Agent Using Carboxybetaine Zwitterionic Tantalum Oxide Nanoparticles

Fitzgerald

Butts

Roberts³

et al. 2016

Invest Radiol

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Objectives To produce and evaluate a proposed computed tomography (CT) contrast agent based on carboxybetaine zwitterionic (CZ) coated soluble tantalum oxide nanoparticles (CZ-TaO NPs). We chose tantalum to provide superior imaging performance compared to 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. The aim of this study was to evaluate the imaging, biological, and physicochemical performance of this proposed contrast agent compared to clinically-used iodinated agents. Materials and Methods We evaluated CT imaging performance of our CZ-TaO NPs compared to an iodinated agent in live rats, imaged centrally-located within a tissue-equivalent plastic phantom that simulated a large patient. To evaluate vascular contrast enhancement, we scanned the rats’ great vessels at high temporal resolution during and following contrast agent injection. We performed several in vivo CZ-TaO NP studies in healthy rats to evaluate tolerability. These studies included injecting the agent at the anticipated clinical dose (ACD) and at 3 times and 6 times the ACD, followed by longitudinal hematology to assess impact to blood cells and organ function (from 4 hours to 1 week). Kidney histological analysis was performed 48 hours after injection at 3 times the ACD. We measured the elimination half-life of CZ-TaO NPs from blood, and we monitored acute kidney injury biomarkers with a kidney injury assay using urine collected from 4 hours to 1 week. We measured tantalum retention in individual organs and in the whole carcass 48 hours after injection at ACD. CZ-TaO NPs were synthesized and analyzed in detail. We used multi-dimensional nuclear magnetic resonance (NMR) to determine surface functionality of the nanoparticles. We measured nanoparticle size and solution properties (osmolality and viscosity) of the agent over a range of tantalum concentrations, including the high concentrations required for standard clinical CT imaging. Results CT imaging studies demonstrated image contrast improvement of approximately 40–50% using CZ-TaO NPs compared with an iodinated agent injected at the same mass concentration. Blood and organ analyses showed no adverse effects following injection in healthy naïve rats at 3 times the ACD. Retention of tantalum at 48 hours after injection was less than 2% of the injected dose in the whole carcass, which very closely matched the reported retention of existing commercial iodine-based contrast agents. Urine analysis of sensitive markers for acute kidney injury showed no responses at 1 week following injection at 3 times the ACD; however, a moderate response in the neutrophil gelatinase-associated lipocalin (NGAL) biomarker was measured at 24 and 48 hours. Compared to other tantalum oxide nanoparticles reported in the literature, CZ-TaO NPs had relatively low osmolality and viscosity at concentrations >200 mg Ta/mL, and were similar in these physical properties to dimeric iodine-bas...

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Multi‐“Color” Delineation of Bone Microdamages Using Ligand‐Directed Sub‐5 nm Hafnia Nanodots and Photon Counting CT Imaging

Ostadhossein

Tripathi

Benig

et al. 2019

Adv Funct Materials

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The early detection of bone microdamages is crucial to make informed decisions about the therapy and taking precautionary treatments to avoid catastrophic fractures. Conventional computed tomography (CT) imaging faces obstacles in detecting bone microdamages due to the strong self‐attenuation of photons from bone and poor spatial resolution. Recent advances in CT technology as well as novel imaging probes can address this problem effectively. Herein, the bone microdamage imaging is demonstrated using ligand‐directed nanoparticles in conjunction with photon counting spectral CT. For the first time, Gram‐scale synthesis of hafnia (HfO2) nanoparticles is reported with surface modification by a chelator moiety. The feasibility of delineating these nanoparticles from bone and soft tissue of muscle is demonstrated with photon counting spectral CT equipped with advanced detector technology. The ex vivo and in vivo studies point to the accumulation of hafnia nanoparticles at microdamage site featuring distinct spectral signal. Due to their small sub‐5 nm size, hafnia nanoparticles are excreted through reticuloendothelial system organs without noticeable aggregation while not triggering any adverse side effects based on histological and liver enzyme function assessments. These preclinical studies highlight the potential of HfO2‐based nanoparticle contrast agents for skeletal system diseases due to their well‐placed K‐edge binding energy.

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CT Image Contrast of High-ZElements: Phantom Imaging Studies and Clinical Implications

Cited by 78 publications

References 38 publications

Complementary contrast media for metal artifact reduction in dual-energy computed tomography

Complementary contrast media for metal artifact reduction in dual-energy computed tomography

A Proposed Computed Tomography Contrast Agent Using Carboxybetaine Zwitterionic Tantalum Oxide Nanoparticles

Multi‐“Color” Delineation of Bone Microdamages Using Ligand‐Directed Sub‐5 nm Hafnia Nanodots and Photon Counting CT Imaging

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