Quantitative parameters in novel spectral computed tomography: Assessment of Ki-67 expression in patients with gastric adenocarcinoma

Figure 2  Boxplots showing a comparison between low and high Ki-67 expression status demonstrated by computed tomography attenuation value of 40 kilo electron volt, 70 kilo electron volt, 100 kilo electron volt, slope of the spectral curve, iodine concentration, the normalized iodine concentration, effective atomic number, and normalized effective atomic number in both arterial phase and venous phase. A: Computed tomography attenuation value of 40 kev; B: Computed tomography attenuation value of 70; C: Computed tomography attenuation value of 100; D: The slope of the spectral curve; E: Iodine concentration; F: The normalized iodine concentration; G: Effective atomic number; H: Normalized effective atomic number. HU: Hounsfield unit; AP: Arterial phase; VP: Venous phase; IC: Iodine concentration; nIC: The normalized iodine concentration; CT_{40 kev,} CT_{70 kev} and CT_{100 kev}: The computed tomography attenuation value of 40 kev, 70 kev and 100 kev monochromatic images; Z^eff: Effective atomic number; nZ^eff: The normalized effective atomic number.