Bernhard Schmidt PhD, Presenter: Employee, Siemens AG

Maximilan Theiler, Abstract Co-Author: Employee, Siemens AG

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

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

Johannes Georg Korporaal PhD, Abstract Co-Author: Employee, Siemens AG

Thomas G. Flohr PhD, Abstract Co-Author: Employee, Siemens AG

Dual Energy data can be acquired with different voltage combinations, beam pre-filtrations and dose splitting between high and low kV beam. Depending on the selected acquisitions settings, noise and dual energy signal might vary. We investigated in a phantom experiment the impact of the different settings on the feasibility to detect certain materials and on the uncertainty of quantification.

For our measurements we used a SOMATOM Definition Flash (Siemens Healthcare, Germany). Data were acquired for three different voltage combinations (80kV/140kV, 80kV/140SN kV and 100kV/140SN). In addition, the mAs values were for one set of measurements adjusted to achieve same dose in the high and low kV beam; for an other set of measurements same mAs were used for both beams. To assess the ability for material quantification, we diluted contrast agents based on iodine (I), gadolinium (Ga), iron (Fe) and ytterbium (Yb) in water to obtain the following concentrations: 0.1, 0.5, 1, 2, 4, 6, 8, 10, 15 and 20 mg/ml. For the dual energy processing a modified version of the three material decomposition technique was used. Dual energy ratio (R = HU at low kV/HU at high kV), material concentration (C) and noise (SD) was determined for all assessed combinations.

Dual energy ratio R was not impacted by the distribution of dose between both beams (same dose vs. same mAs). However, scans with tin filtration (SN) leaded to significantly higher values for R: I 2.0, 3.1 and 2.3; Ga 1.6, 2.1 and 1.8; Fe 2.0, 2.8 and 2.1; Yb 1.3, 1.4 and 1.4 for 80kV/140kV, 80kV/140SN kV and 100kV/140SN respectively. The higher the dual energy ratio R, the lower was SD in the post-processed images. Measurements with same mAs for both beams leaded to substantially higher SD values and reduced the ability for material detectability compared to the scans with same dose.   

Same dose values in the high and low kV beam in combination with an additional tin filtration increased substantially the ability to detect materials and it improved the precision of quantitative values.

To optimize the results of post-processed dual data scans, optimal distribution of dose and a high spectral separation is recommended.

Schmidt, B, Theiler, M, Krauss, B, Pietsch, H, Korporaal, J, Flohr, T, Assessment of the Impact of Dual-Energy Acquisition Parameters on the Possibility for Material Detection and Precision of Material Quantification.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043894.html