ARRS 2022 Abstracts

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E1537. Signal Characteristics of Conventional vs Experimental Dark Oral and Experimental Tantalum Contrast Agents at Dual-Energy CT
Authors
  1. Samuel Shu; Frank H Netter MD School of Medicine, Quinnipiac University
  2. Yuxin Sun; Department of Radiology and Biomedical Imaging, University of California - San Francisco
  3. Peter Bonitatibus; Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute
  4. Benjamin Yeh; Department of Radiology and Biomedical Imaging, University of California - San Francisco
Objective:
In over half of the 91 million CT studies performed in the United States annually, contrast agents are routinely administered to obtain crucial diagnostic information. Iodine is currently the only intravenous contrast material in common clinical use, and no substantial innovations in contrast materials have been made in over 30 years. Experimental noniodinated contrast materials have the potential to improve clinical diagnosis for both conventional CT and dual energy CT (DECT); however, DECT systems are known to have intersystem differences in material quantification. Our study aims to characterize the signals of experimental and conventional contrast materials for different clinical DECT systems.

Materials and Methods:
Samples of iodine, gadolinium, an experiment dark borosilicate contrast material (DBCM), an experimental carboxybetaine zwitterionic tantalum oxide (TaCZ) contrast agent, and an experimental lanthanide agent were prepared in a range of concentrations and placed inside a phantom simulating the mass of an adult human abdomen. The phantom was scanned using five different clinical DECT systems: GE Revolution CT 64, GE Revolution CT 256, Siemens SOMATOM Flash, Siemens SOMATOM Force, and Philips IQon Spectral CT. Iodine maps and conventional 120-kVp-like and virtual monoenergetic image (VMI) reconstructions were obtained in the range of energies available on each system. The mean HU values of each contrast material sample were measured to assess material attenuation behavior and intersystem differences.

Results:
For all scanners, the polychromatic attenuation curve of TaCZ peaked at 100 HU with decreasing HU at higher kVp thereafter and similar HU values at low (70 and 80 kVp) and high (140 and 150 kVp) tube potentials, whereas all other materials showed only decreasing attenuation with increasing kVp. The HU ranges of both TaCZ and DBCM profiles were relatively narrow compared to all other materials for different kVp settings and keV DECT reconstructions. From low to high virtual monoenergetic images, the HU values of all materials exponentially decreased, with the exception of TaCZ and DBCM as imaged on the Philips IQon and GE Revolution 256, respectively, which exponentially increased. Iodine quantification images showed the superior ability of each system to differentiate the TaCZ and DBCM contrast agents better than gadolinium and lanthanide agents from iodine. Scanner-specific mass attenuation coefficients were also derived from VMI HU values for each material to enable reconciliation of differences between DECT systems.

Conclusion:
Experimental contrast agents differ substantially in their DECT attenuation profiles compared to iodine agents, and these differences should enable reliable signal separation from conventional contrast materials once clinically approved.