| Calibration Material | Bulk density ρ (g∙cm−3) | X-ray CT Attenuation Coefficient | |
| HU (-) | σ (-) | ||
| Air | 0.00 | −1000 | - |
| Pure water | 1.00 | 0 | - |
| Plastic | 1.10 | 115 | 9 |
| Glass | 2.15 | 1492 | 12 |
| Aluminum | 2.70 | 2810 | 22 |