# Enhancing Soft Tissue Differentiation with Different Dual-Energy CT Systems: A Phantom Study
## 4 Discussion
 } & \multicolumn{4}{c}{**Mean Difference in HU (95\% CI)**} \\ \cline{3-6}  & & **Siemens** & **Siemens** & **Siemens** & **GE** \\  & & **Confidence** & **Edge** & **Force** & **Revolution GSI** \\ \hline Adipose & 40 keV & **29.7** (28.4; 30.9) & **14.4** (11.5; 17.2) & **22.2** (19.4; 25.1) & **36.0** (35.1; 37.0) \\ \cline{2-6} vs. & 50 keV & **16.1** (15.2; 17.0) & **5.7** (4.0; 7.5) & **8.4** (6.4; 10.5) & **19.2** (18.6; 19.9) \\ \cline{2-6} Breast & 70 keV & **2.8** (2.2; 3.4) & **-2.6** (-3.5; -1.7) & -0.8 (-1.5; 0.0) & **1.9** (1.5; 2.4) \\ \hline Adipose & 40 keV & **73.9** (72.5; 75.2) & **89.4** (87.6; 91.3) & **79.2** (75.9; 82.6) & **93.6** (92.3; 94.8) \\ \cline{2-6} vs. & 50 keV & **40.5** (39.5; 41.4) & **48.3** (47.1; 49.4) & **39.1** (37.1; 41.2) & **47.9** (47.0; 48.9) \\ \cline{2-6} Muscle & 70 keV & **7.8** (7.2; 8.3) & **8.0** (7.3; 8.7) & **2.9** (1.8; 3.9) & **1.8** (1.1; 2.5) \\ \hline Adipose & 40 keV & **75.3** (74.3; 76.2) & **97.4** (94.6; 100.2) & **67.6** (66.1; 69.2) & **96.5** (95.0; 98.0) \\ \cline{2-6} vs. & 50 keV & **41.1** (40.4; 41.8) & **55.3** (53.4; 57.2) & **31.6** (30.3; 32.9) & **49.7** (48.7; 50.6) \\ \cline{2-6} Liver & 70 keV & **7.6** (7.2; 8.1) & **14.1** (13.0; 15.2) & 0.2 (-0.6; 1.0) & **2.3** (1.7; 2.9) \\ \hline Breast & 40 keV & **349.3** (347.8; 350.7) & **471.3** (469.3; 473.4) & **376.9** (374.1; 379.7) & **348.0** (345.5; 350.5) \\ \cline{2-6} vs. & 50 keV & **189.9** (188.9; 191.0) & **265.1** (263.6; 266.6) & **192.9** (190.6; 195.1) & **181.3** (179.3; 183.3) \\ \cline{2-6} Bone 200 mg & 70 keV & **33.4** (32.7; 34.0) & **62.3** (61.0; 63.5) & **11.6** (9.7; 13.5) & **10.5** (9.7; 11.4) \\ \hline Muscle & 40 keV & 1.4 (0.1; 2.7) & **8.4** (5.5; 11.3) & **-2.5** (-4.1; -0.9) & 2.9 (1.3; 4.5) \\ \cline{2-6} vs. & 50 keV & 0.7 (-0.3; 1.6) & **7.0** (4.9; 9.1) & **-4.6** (-5.7; -3.6) & 1.7 (0.7; 2.7) \\ \cline{2-6} Liver & 7 increased as the energy level decreased in all pairwise comparisons of soft-tissue inserts. Notably, adipose and breast tissues showed superior discrimination, using 40-50 keV DECT images compared to SECT images across all CT scanners. However, the discrimination between muscle and liver using DECT images, while statistically significant in some instances, demonstrated relatively small differences (<10 HU) compared to SECT images for all scanners, suggesting limited clinical utility in those scenarios. When comparing results across different technologies, the following observations were made. Adipose vs. breast showed that the GE system effectively discriminates these two tissues using energies at 40-50 keV. However, at higher reconstruction energies, Confidence prevails. Adipose vs. muscle showed that the GE system distinctly discriminates adipose and muscle tissues at 40 keV. At 50 keV, Edge becomes the preferable discriminator, while at 70 keV, both Confidence and Edge demonstrate equal discriminative power. Adipose vs. liver shows that at 40 keV, the GE and Edge systems perform similarly in tissue discrimination. However, at 70 keV, Edge emerges as the superior discriminator between these tissues. Breast vs. bone (200 mg) shows that Confidence and GE show equivalent discrimination abilities at 40-50 keV, while Edge outperforms them all at 70 keV. Muscle vs. liver shows that Edge is better suited for discriminating between these soft tissues at lower energies. The results showed that, although low energies are desirable for optimal contrast, they suffer from increased noise and reduced accuracy in CT number quantification. In particular, for all tissues, Siemens Edge CT exhibited a deviation in average mean CT numbers compared to the other evaluated CT scanners. This difference is evident in the muscle and liver inserts, where the average CT numbers at low energies (40-50 keV) were particularly divergent. Furthermore, the coefficient of variation was assessed, which shows a dispersion of values that were around the mean of 7% for the breast and liver, 5% for muscle and bone 200 mg, and 2% for adipose.