Table 2.
Intra-slice variation as compared to inter-slice variation
| Liver | Spleen | Muscle | |||||
|---|---|---|---|---|---|---|---|
| Mean Δ (HU) | SD of mean Δ (HU) | Mean Δ (HU) | SD of mean Δ (HU) | Mean Δ (HU) | SD of mean Δ(HU) | ||
| Within slice * | Chest | 6.7 | 3.8 | 12.2 | 11.6 | 7.5 | 4.9 |
| Between slices ** | Chest | 3.9 | 3.3 | 7 | 3.6 | 7.6 | 4.9 |
| Within slice * | Abdomen | 3.1 | 2.3 | 3.5 | 1.6 | 7.1 | 4.8 |
| Between slices ** | Abdomen | 1.8 | 1.2 | 3 | 1.6 | 7.7 | 4.9 |
The Hounsfield units from two measures in the liver (left and right lobe), spleen or paraspinal muscles within one slice were subtracted from each other to calculate the within one slice differences (one for each of two separate slices) and the two measures averaged to get the mean delta and SD for the within slice categories.
The Hounsfield units from two measures in the liver, spleen, or paraspinal muscles were subtracted from parallel measures in an adjacent slice to obtain the between slices differences. These two between slices measures were averaged to obtain the mean delta and SD for the between slices categories.