Dual-Energy CT-Based Material Decomposition for Stoichiometric Calibration of DCE CT
C Coolens1,2*, G Landry3, C Varon1, F Verhaegen3, (1) Princess Margaret Cancer Centre and University Health Network, Toronto, ON, Canada, (2) University of Toronto, ON, Canada,(3) MAASTRO Physics, MaastrichtSU-E-I-19 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: To improve the sensitivity and accuracy of contrast-enhanced CT measurements by using atomic number extraction of Iodine-based contrast agent concentration from dual energy CT (DECT) material decomposition.
Methods:Dual energy scans of different levels of CT contrast agent concentrations (range 0- 67.5 mgI/mL) were acquired in a body phantom on a 320-slice single-source CT scanner (Toshiba, Aquilion 1) at 80 and 135kVp using 300mAs to minimize noise. The X-ray spectrum was modeled with SpekCalc by adjusting nominal tube filtration to match measured half value layers at all available energies. From the CT images, the effective atomic number Zeff of the different contrast materials was calculated using DECT material decomposition written in Matlab™ and electron density values relative to water ρe/w were obtained. A stoichiometric calibration for DCE CT was done two-fold: (a) using ρe/w per conventional single-energy CT; and (b) employing also Zeff from DECT. Resulting accuracy of contrast concentration values were compared against known elemental compositions and the sensitivity and CNR of methods assessed.
Results:Using only ρe/w resulted in poor differentiation of contrast concentration levels, with an increase in ρe/w of only 0.5% per mgI/mL. Performing the material decomposition from DECT resulted in a much wider dynamic range of Zeff per mgI/mL through its power of three dependency. DECT estimates of Zeff and ρe/w were within (9.4 ± 6.4%) and (2.1 ± 9.5%) from theoretical calculations based on dilutions of Visipaque™320 in water, with the largest deviations starting to appear above 30mgI/mL. Similar results were found from DECT analysis based on (80-120kV) scans (within 4.5%).
Conclusion:DECT material decomposition is showing promise to increase the dynamic range and signal to noise ratio of contrast-enhanced CT imaging. Future work will explore dynamic DECT of contrast enhancement.