Alex Justin Lewis MD, Presenter: Nothing to Disclose

Felix G. Meinel MD, Abstract Co-Author: Nothing to Disclose

Andrew Douglas McQuiston BS, Abstract Co-Author: Nothing to Disclose

Bernhard Schmidt PhD, Abstract Co-Author: Employee, Siemens AG

Steffen Kappler DIPLPHYS, Abstract Co-Author: Researcher, Siemens AG

U. Joseph Schoepf MD, Abstract Co-Author: Research Grant, Bracco Group Research Grant, Bayer AG Research Grant, General Electric Company Research Grant, Siemens AG

Gregor Jost PhD, Abstract Co-Author: Employee, Bayer AG

Hubertus Pietsch PhD, Abstract Co-Author: Employee, Bayer AG

Christian Canstein, Abstract Co-Author: Employee, Siemens AG

Recently developed energy resolved photon-counting detectors allow high Z materials to be effectively separated based on their absorption characteristics in the energy range of interest. Importantly, this allows contrast agents (CA) that contain different materials to be separated based on the incident X-ray spectrum. The aim of this study was to evaluate the characteristics and optimal combination of three different contrast agents by using a research prototype CT unit with small pixel counting photon detectors.

To demonstrate proof-of-principle, experimental bismuth, tungsten and iodine CA were introduced into a chest phantom utilizing a two-threshold energy resolved photon-counting detector. Standard tube voltage (120kV) and tube current (80mAs) were applied with a photon counting detector using energy thresholds of 25keV and 65keV allowing reconstruction into three energy bins: 25keV to 120keV, 65keV to 120keV and 25keV to 65keV. Region of interest analysis was performed to assess attenuation patterns, contrast to noise ratios and identify optimal contrast agent combination for discrimination by the photon counting detector.

The CT acquisitions revealed strong contrast enhancement within the chest phantom with excellent contrast to noise ratios and differentiation of photon energies for each contrast agent by the photon counting detectors. Contrast materials could be uniquely identified by their characteristic attenuation profile at each energy threshold. Based on attenuation characteristics and contrast to noise ratios, the optimal contrast agent combination for scanning with photon counting detector CT technology appears to be iodine and tungsten with energy bins corresponding to an average X-ray energy of 62.5keV and 73keV.

The separation of three simultaneously administered contrast agents is feasible with the use of an energy selective, photon counting detector in CT. Spectral CT has the potential to enable distinct characterization of contrast agents in a chest phantom with the optimal contrast agent pair being iodine and tungsten with detector energy bins corresponding to an average X-ray energy of 62.5keV and 73keV.

The separation of contrast agents with different pharmacokinetics utilizing photon counting technology may lend itself to a variety of beneficial applications in future contrast enhanced CT.

Lewis, A, Meinel, F, McQuiston, A, Schmidt, B, Kappler, S, Schoepf, U, Jost, G, Pietsch, H, Canstein, C, Spectral CT Characteristics of Iodine, Bismuth, and Tungsten Based Contrast Media with an Energy-Resolving Photon-Counting Detector.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14004385.html