Figure 1.
Dual-energy data post-processing.
a Dual-energy portal venous phase image, b fused image of virtual 120-kV data sets with the color map of iodine distribution, c virtual non-enhanced image after iodine subtraction.
Figure 2.
Standard values applied for analysis of soft-tissue and fat-tissue attenuation.
Table 1.
Mean Length, CT value and noise of ROI measured in three series of non-enhanced images.
Figure 3.
Proportion of measurements stratified per tissue type, with an absolute difference of >10 and >15 Hounsfield units between TNE and VNE images.
a Proportion of measurements stratified per tissue type, with an absolute difference of >10 and >15 Hounsfield units between TNE and VNEA images. b Proportion of measurements stratified per tissue type, with an absolute difference of >10 and >15 Hounsfield units between TNE and VNEP images.
Figure 4.
VNE images were acceptable for diagnosis purpose.
a∼d A 56-year-old man with advanced gastric cancer in the lesser curvature of the antrum. a Transverse CT scans show focal wall thickening (asterisk) of the lesser curvature of the gastric antrum with abnormal enhancement. VNEA image (c), VNEP image (d) and TNE image (b) show good correlation of measured CT numbers and thickness of the tumor (TNE: 39.7 HU±9.6, 1.84 cm; VNEA: 37.3 HU±8.1, 1.58 cm; VNEP: 38.3 HU±6.4, 1.90 cm). e∼h A 62-year-old man with advanced gastric cancer in the fundus. e Transverse CT scans show an enlarged lymph node (arrow) in the lesser curvature of the gastric body. VNEA image (g), VNEP image (h) and TNE image (f) show good correlation of measured CT numbers and diameter of the node (TNE: 37.6 HU±8.6, 1.66 cm; VNEA: 40.0 HU±6.2, 1.77 cm; VNEP: 34.1 HU±5.3, 1.71 cm). Both of the patients are noted excellent VNE image quality.
Figure 5.
More obvious overshooting artifact at the gas-fluid level (arrow) was detected in VNE image.
a. TNE image; b. VNE image.
Figure 6.
The yellow circle relates to the smaller (33 cm) field of view of the smaller detector. Iodine maps and subsequent iodine subtraction to create the virtual non-enhanced images can only be performed within the circle. In larger patients (>40 cm actual body diameter) or patients with improper position important anatomy may be excluded from the subtraction. In this example the lateral aspect of the right lobe of the liver fails to ‘become unenhanced’ (arrows).
Table 2.
Image quality true non-enhanced and virtual non-enhanced images.