Xiangpeng Zheng, Presenter: Nothing to Disclose

Yanqing Hua MD, Abstract Co-Author: Nothing to Disclose

Gang Shen, Abstract Co-Author: Nothing to Disclose

Jian Ying Li PhD, Abstract Co-Author: Employee, General Electric Company

Yun Shen PhD, Abstract Co-Author: Employee, General Electric Company

Guo-Zhen Zhang MD, Abstract Co-Author: Nothing to Disclose

To assess the quantification of iodine and calcium with material decomposition algorithm in gemstone spectral imaging (GSI) for establishing correlations between actual material concentration and CT attenuation for perfusion study and calcification quantification.

Phantom with 18 iodine concentrations (Iopamidol, 0.35mgI/ml to 15.75mgI/ml) and 10 calcium concentrations (calcium glucose diluted with water, 0.01g/ml to 0.1g/ml) was constructed in 15ml Corning tubes with 10mm in-between. The phantom was scanned with GSI mode on HDCT (GE Discovery CT750 HD) with instantaneous 140 and 80kVp switching. A set of monochromatic images was reconstructed with 2.5mm thickness/interval at the default 60keV single energy. The reconstructed imaging data were post-processed with GSI imaging analysis software package (GSI Viewer) for material decomposition and characterization. CT attenuation values, iodine concentration (on water-iodine bases) and calcium concentration (on water-calcium bases) measured with consistent regions of interest (ROIs) placed in the tube center with a diameter of two thirds of the tube diameter. The actual iodine and calcium concentration was correlated to the measured concentrations and CT attenuation values.

Both iodine and calcium solution increasingly attenuated X ray with concentration increasing. The measured iodine concentration was highly consistent with actual concentration (p>0.05). The minimal measurable iodine concentration was as low as 0.35mgI/ml, corresponding to CT value of 3.33±4.03HU at 65keV. Iodine concentrations (x) correlated to mean CT values (y) by an equation of y=34.10x-12.13 (R2=0.995). The minimal measurable calcium concentration was 0.4g/ml and the correlation equation between calcium concentrations (x) and CT values (y) was y=613.82x-8.82 (R2=0.974).

GSI-based material decomposition provided an accurate quantitative approach to directly retrieve iodine and calcium amount from monochromatic images, which established the groundwork for quantitative assessment of iodine or calcium in patients.

Iodine and calcium can be accurately quantitatively measured according to their specific attenuation pattern in spectral imaging, which is important for tissue characterization and perfusion studies.

Zheng, X, Hua, Y, Shen, G, Li, J, Shen, Y, Zhang, G, Iodine and Calcium Quantization with Material Decomposition Algorithm in Spectral CT Imaging: An Experimental Study.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9010981.html