Philipp Riffel MD, Presenter: Nothing to Disclose

Stefan Haneder MD, Abstract Co-Author: Nothing to Disclose

Holger Haubenreisser, Abstract Co-Author: Nothing to Disclose

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

Stefan Oswald Schoenberg MD, PhD, Abstract Co-Author: Institutional research agreement, Siemens AG

Thomas Henzler MD, Abstract Co-Author: Nothing to Disclose

Previous studies demonstrated that calculated low keV monoenergetic datasets from Dual energy (DE)CT abdominal angiography imaging does not significantly improve contrast-to-noise ratio (CNR) when compared to polyenergetic images (PEI), which is due to the dramatic increase in image noise at lower keV levels. The recently introduced frequency-split technique combines the lower spatial frequency stack at low keV for high contrast with the high spatial frequency stack for image noise at high keV levels to calculate noise-reduced images at ultra-low keV levels below 70 keV. The aim of this study was to compare objective image quality indices in DECT angiography studies of the abdomen using conventional polyenergetic images (PEIs) and virtual monoenergetic images (MEIs) at different keV levels using the frequency-split technique.

20 patients (14 male; mean age 70±10 years) who underwent DECT angiography of the abdomen were retrospectively included in this study. MEIs from 40 to 120 keV were reconstructed using the frequency-split technique. Signal intensity, noise, signal-to-noise ratio (SNR) and CNR were assessed in infrarenal aorta, superior mesenteric and external iliac arteries. Comparisons between MEIs and PEIs were performed using a Mann-Whitney U test.

60 arteries were evaluated. 40 keV MEIs resulted in significantly higher signal intensity (+254% on average; all p 0.05). Highest CNR values were found in 40 keV MEIs (9 ± 0.8 HU, 7 ± 1.6 HU, 9 ± 1.4 HU in the infrarenal aorta, superior mesenteric and external iliac arteries, respectively), which were significantly higher compared to PEI (7 ± 1 HU, 5 ± 1.5 HU, 7 ± 1.5 HU in the infrarenal aorta, superior mesenteric and external iliac arteries, respectively, all p < 0.05).

Combining the lower spatial frequency stack for contrast at low keV levels with the high spatial frequency stack for noise at high keV levels leads to improved image quality of ultra-low keV monoenergetic abdominal DECT datasets when compared to previous monoenergetic reconstruction techniques without the frequency-split technique.

With a frequency split approach, 40 keV MEIs provide improved objective image quality in DECT abdominal angiography compared to standard PEI. Their additional reconstruction might improve diagnostic accuracy.

Riffel, P, Haneder, S, Haubenreisser, H, Schmidt, B, Schoenberg, S, Henzler, T, Abdominal Dual-Energy CT Angiography: Evaluation of Ultra-low keV Calculated Monoenergetic Datasets by Means of a Frequency-Split Approach for Noise Reduction at Ultra-low keV Levels.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012833.html