Table 3. Mean Hounsfield units, image noise and contrast-to-noise ratio (CNR) measured on three linear mixed image sets, and on 80 and 140 kVp images.
| TNE | VNE | 140 kVp | Weighting factor |
80 kVp | p-value | |||
| 0.3 | 0.5 | 0.7 | ||||||
| Hounsfield units | ||||||||
| Normal pancreas | 38.9±9.7 | 36.9±11.6 | 107.6±14.6 | 123.0±20.2 | 137.0±20.1 | 151.2±25.8 | 187.9±24.3 | |
| Lesion (cystic, n=19) | 14.7±10.5 | 9.5±18.8 | 33.9±51.0 | 37.9±56.6 | 43.3±68.0 | 43.5±69.3 | 54.5±84.8 | |
| Lesion (solid, n=25) | 33.4±14.2 | 32.7±14.7 | 59.0±41.1 | 70.1±44.8 | 83.9±48.3 | 93.2±56.4 | 105.1±75.4 | |
| Hypovascular (n=21) | 30.0±9.0 | 28.9±11.6 | 45.8±19.8 | 56.3±22.4 | 67.7±23.4 | 73.3±24.7 | 77.5±28.7 | |
| Hypervascular (n=4) | 39.1±0.5 | 41.7±6.5 | 128.3±57.1 | 142.0±64.9 | 164.6±65.7 | 185.5±79.6 | 233.4±104.2 | |
| Image noisea | 12.8±3.6 | 15.4±3.5 | 17.0±3.6 | <0.0001b | ||||
| CNR (cystic, n=19) | 8.0±2.6 | 7.6±2.5 | 7.3±1.9 | 0.0325b | ||||
| CNR (solid, n=25) | 5.6±3.0 | 5.2±2.6 | 4.8±3.1 | >0.05b | ||||
| Hypovascular (n=21) | 6.3±3.7 | 5.6±2.7 | 5.3±3.3 | 0.0333 | ||||
| Hypervascular (n=4) | 4.4±2.4 | 3.5±2.0 | 3.7±2.4 | 0.1132 | ||||
TNE, true non-enhanced; VNE, virtual non-enhanced.
aImage noise refers to standard deviations of the retroperitoneal fat, CNR=(ROIL–ROIP)/σ(ROIRf), where ROIL is the mean attenuation value of the pancreatic lesion, ROIP is the mean attenuation value of the normal pancreatic parenchyma and σ(ROIRf) is the standard deviation of attenuation values of retroperitoneal fat.
bp-value comparing each value from the images with weighting factor 0.3 vs 0.5, 0.5 vs 0.7, 0.3 vs 0.7.