Jian He MD, PhD, Presenter: Nothing to Disclose

Kefeng Zhou, Abstract Co-Author: Nothing to Disclose

Xiao Zhu Lin BA, Abstract Co-Author: Nothing to Disclose

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

Shuai Zhang, Abstract Co-Author: Nothing to Disclose

Bin Zhu MD, PhD, Abstract Co-Author: Nothing to Disclose

Junkun Chen, Abstract Co-Author: Nothing to Disclose

To compare the correlation between iodine concentration and CT value and that between iodine concentration and the slope of spectral curve by a phantom in different movement states with different rotation times of X-ray tube.

Nine test tubes with different iodine concentrations (0.8-100 mgI/ml) set in a phantom were scanned with gemstone spectral imaging (GSI) mode (fast tube voltage switching between 80 and 140kvp, 600mA) on Discovery HD750 CT (GE Healthcare, Waukesha, Wis) in different movement states (direction: up and down, range (mm)/ frequency (beats per minute): 5/5, 5/10, 10/5, 10/10) with different rotation times of X-ray tube (0.6s, 0.8s, 1.0s). Conventional 140 kVp polychromatic images and 101 sets of monochromatic images (40-140keV) were generated automatically. CT values (HU) were measured on polychromatic images. The slope of spectral curve equaled to ΔCT value (between 90keV and 140keV) divided by 50. Correlations between iodine concentration and CT value / the slope of spectral curve were calculated by correlation and regression analysis and compared with paired t test.

There were no significant differences of CT values and slopes of spectral curves with different rotation times in the state of rest (p>0.05). Correlation between iodine concentration and slope of spectral curve (r2>0.999, p<0.001) was higher than that between iodine concentration and CT value (r2>0.997, p<0.001) in each state with each rotation time. There were no significant differences of CT values and slopes of spectral curves between rest and movement (5/5) (p>0.05). And there were no significant differences of CT values between rest and movements (5/10, 10/10) (p>0.05).

The slope of spectral curve reflects the iodine concentration more accurately than CT values. Rotation times of 0.6s and 0.8s of GSI mode could reduce the effect of movement on the measurement of CT value and the slope of spectral curve.

The slope of spectral curve may be a new index of enhancement degree. Some forms of physiological movements could be conquered by a shorter rotation time of GSI mode.

He, J, Zhou, K, Lin, X, Shen, Y, Zhang, S, Zhu, B, Chen, J, Correlation between Iodine Concentration and CT Value or the Slope of Spectral Curve: Which Is Better? A Phantom Study in Different States with Different Rotation Times.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034445.html