Table 1.
Summary of mean unenhanced attenuation and percentage of negative voxels in adrenal masses.
| Adenomas | Pheochromocytomas | Carcinomas | Metastases | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Med | Min | Max | Mean | SD ** | Med | Min | Max | Mean | SD ** | Med | Min | Max | Mean | SD ** | Med | Min | Max | Mean | SD ** | p | |
| (a) | |||||||||||||||||||||
| mean unenhanced attenuation (HU) | 6 | −23 | 50 | 9.6 | 14.3 | 34 | 17 | 80 | 33 | 8.5 | 30.5 | 24 | 41 | 31.6 | 5.2 | 32.5 | 9 | 56 | 32.4 | 8.8 | <0.0001 |
| (b) | |||||||||||||||||||||
| percentage of negative voxels (%) | 37.7 | 0 | 86.2 | 36.2 | 22.7 | 1.5 | 0 | 9.8 | 2.75 | 2.91 | 2.55 | 0 | 9.9 | 3.08 | 2.98 | 3.1 | 0 | 34.1 | 4.4 | 6.4 | <0.0001 |
| (c) | |||||||||||||||||||||
| standard deviation of HU values * | 16.9 | 7.1 | 29.5 | 17.5 | 5.1 | 15.9 | 5.9 | 24.6 | 15.6 | 3.9 | 14.6 | 8.3 | 21.7 | 15.1 | 3.9 | 16.6 | 6.6 | 27 | 16.5 | 4.1 | 0.0728 |
Med—median, Min—minimum, Max—maximum, SD—standard deviation, p—significance level calculated by Kruskal–Wallis test. * standard deviation of Hounsfield values measured inside each adrenal mass to quantify CT image noise, as demonstrated in Figure 1; ** standard deviation as a measure of the variability of the mean unenhanced attenuation; the percentage of negative voxels; and the standard deviation of HU values in the group of adenomas, pheochromocytomas; carcinomas, and metastases.