Fig 1.
Attenuation values assessed in the suprarenal aorta in arterial and venous contrast phase imaging.
The highest values are found for MonoE at 40 keV reconstruction level, respectively. (values: mean ± SD)
Fig 2.
Image noise for the whole energy spectrum from 40 to 200 keV in both contrast phases (values: Mean ± SD).
Note that image noise values are not significantly increased in the low keV MonoE reconstruction levels compared to the high keV reconstructions.
Table 1.
Contrast-to-noise (CNR) values (mean ± SD) of conventional and virtual mono-energetic images (all keV levels) split for all anatomic regions and separately given for arterial and venous phase.
Table 2.
Signal-to-noise (SNR) values (mean ± SD) of conventional and virtual mono-energetic images (all keV levels) split for all anatomic regions and separately given for arterial and venous phase.
Fig 3.
Absolute attenuation, standard deviation (SD), SNR and CNR in the infrarenal aorta in arterial contrast phase imaging for conventional and MonoE reconstructions.
Due to the substantial increase of absolute attenuation and constantly low SDs, SNR and CNR values are markedly elevated at low keV reconstruction levels (Values: Mean ± SD).
Fig 4.
Waterfall plot showing overall image quality rating in arterial and venous contrast phase with standard abdominal window settings where 0 corresponds to the reference standard (conventional imaging).
Best image quality was rated for MonoE at 70 keV in arterial and 80 keV in venous phase.
Fig 5.
SDCT images of an 83-year old patient in arterial and venous contrast phase.
For a more realistic comparability window settings were kept constant (center 60 HU; width 360 HU), except for the 40 keV MonoE reconstructions with adjusted window settings. Compared to conventional images MonoE at low keV reconstruction levels showed increased attenuation and contrast without excessive noise in both contrast phases. If window levels were adjustable MonoE at 40 keV was rated best for overall image quality, whereas reconstruction levels of 70 keV were rated best and superior to conventional images if readers were not allowed to adjust window settings. Note extensive increase in parenchymal attenuation in venous contrast phase in MonoE at 40 keV reconstruction level with standard windowing presets.
Table 3.
Qualitative image analysis (subjective image contrast, subjective visualization of details, subjective overall image quality) of the virtual mono-energetic images (all keV levels) given as means ± SD split for arterial and venous phase.