Daniele Marin MD, Presenter: Nothing to Disclose

Joshua Wilson PhD, Abstract Co-Author: Research support, General Electric Company

Amy Marie Neville MD, Abstract Co-Author: Nothing to Disclose

James G. Colsher PhD, Abstract Co-Author: Employee, General Electric Company

Sebastian Tobias Schindera MD, Abstract Co-Author: Research grant, Siemens AG

Daniela Barbara Husarik MD, Abstract Co-Author: Nothing to Disclose

Timothy Turkington PhD, Abstract Co-Author: Nothing to Disclose

Ehsan Samei PhD, Abstract Co-Author: Advisory Board, Ion Beam Applications, SA Consultant, Siemens AG Research grant, Siemens AG Research grant, General Electric Company Research grant, Carestream Health, Inc

Rendon C. Nelson MD, Abstract Co-Author: Consultant, General Electric Company Research support, Bracco Group Research support, Becton, Dickinson and Company Speakers Bureau, Siemens AG Royalties, Lippincott, Williams & Wilkins

To test the hypothesis that synthesized monochromatic imaging generated from a fast kilovoltage switching dual energy CT acquisition may correct for beam hardening artifacts, yielding uniform aortic enhancement across different body sizes.

A fillable tapered phantom with an oval cross-section ranging from 6.8 cm x 17.8 cm to 38.5 cm x 49.5 cm was used. To simulate typical contrast enhancement in the abdominal aorta, a 2.0 cm x 2.0 cm rubber hose was positioned inside the phantom and filled with a mixture of 1:30 (iodine:water) iodinated contrast material with a concentration of 370 mgI/mL. An equivalent vertebral insert was also used. The phantom was scanned using a dual energy 64-section CT scanner. In addition to the polychromatic 140-kVp source images, synthesized monochromatic datasets were reconstructed at x-ray energies ranging from 40 keV to 140 keV, with 10 keV increments. For each dataset, regions-of-interest (ROI) were drawn in the aortic lumen and background water at eight different locations along the z-axis of the phantom. Aortic attenuation (HU) and signal-to-noise ratio (SNR) were compared in various phantom cross-section areas and among different datasets.

For all datasets, there was a negative correlation between the phantom’s cross-section area and aortic attenuation or SNR. The difference in aortic attenuation between the smallest and largest cross-section area of the phantom was significantly smaller for the 40, 50, 60, 70, and 80 keV datasets (range in CT numbers difference: 0.5 HU [0.2%] at 70 keV, 6.5 HU [3.2%] at 80 keV) compared to the other monochromatic datasets (range: 10.3 HU [7.2%] at 90 keV, 13.5 HU [31.9%] at 130 keV) and the 140-kVp polychromatic dataset (24.3 [9.8%]) (P < .01 for all comparisons). Mean SNR was significantly higher for the 40, 50, 60, and 70 keV datasets (range: 14.1 at 60 keV, 18.0 at 40 keV) compared to the other monochromatic datasets (range: 1.6 at 140 keV, 10.0 at 80 keV) and the 140-kVp polychromatic dataset (12.0) (P < .05 for all comparisons).

Synthesized monochromatic imaging at x-ray energies ranging from 40 to 70 keV may improve the magnitude and uniformity of aortic enhancement for different body sizes.

Synthesized monochromatic imaging has the potential (within a certain range of x-ray energies) to minimize beam hardening artifacts, yielding uniform aortic enhancement across different body size

Marin, D, Wilson, J, Neville, A, Colsher, J, Schindera, S, Husarik, D, Turkington, T, Samei, E, Nelson, R, Effectiveness of Synthesized Monochromatic Imaging Generated with a Fast Kilovoltage Switching Dual-Energy CT Scanner for Improving Patient-to-Patient Uniformity of Aortic Enhancement during Abdominal CT Angiography.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11011718.html