Table 1.

The CT number changes of three materials according to the energy level.

Polyenergetic images
Tube voltage (kVp)	100		120		140
Water (HU)	−3.1 ± 0.3		−2.2 ± 0.5		−1.8 ± 0.6
Oil (HU)	−135.1 ± 0.4		−119.3 ± 0.2		−104.0 ± 0.5
Contrast agent (HU)	682.0 ± 0.5		505.8 ± 0.3		329.0 ± 0.1
Monoenergetic images
Effective energy (keV)	40	70	100	130	160	190
Water (HU)	−7.0 ± 1.0	−2.8 ± 0.4	−1.7 ± 0.6	−1.3 ± 0.7	−1.1 ± 0.8	−1.0 ± 0.8
Oil (HU)	−228.1 ± 2.9	−127.0 ± 0.2	−101.0 ± 0.6	−91.9 ± 0.8	−87.9 ± 0.9	−85.9 ± 1.0
Contrast agent (HU)	1738.0 ± 1.7	590.5 ± 0.5	294.7 ± 0.2	191.2 ± 0.2	146.3 ± 0.2	123.7 ± 0.2

CT: computed tomography.