What is a Grey-Value Image?
A grey-value image is the intensity representation of the reconstructed volume at voxel level. The topic is a methodological foundation for reliable CT data, because it directly affects detection limits, measurement capability and reproducibility.
Scientific background
The scientific basis is rooted in the physical interaction of X-ray radiation with matter and in the mathematical data processing of projections. Particularly relevant are absorption contrast, histogram separation and segmentation. For technical decisions, these relationships must be understood as a quantifiable measurement chain.
Relevant key metrics
- Spatial resolution, contrast-to-noise ratio and measurement uncertainty are the central parameters.
- Systematic effects are controlled via calibration, reference standards and repeat measurements.
- Parameter changes must be evaluated for robustness and transferability to series production conditions.
Standards and thresholds
- Standards: ISO 15708-2:2025 and ISO 15708-3:2025 (data acquisition, operation, interpretation).
- Typical thresholds (in practice): SNR for stable segmentation typically above 10; saturation or clipping within the relevant measurement range must be minimised.
- Validity: Limits are material-, geometry- and task-dependent and must be validated empirically.
Application in industrial practice
- Design of valid scan parameters for defect and measurement tasks.
- Objective interpretation of CT findings in development and series production.
- Comparability of results across systems, batches and time points.
Sources and reference date
- ISO 15708-2:2025.
- ISO 15708-3:2025.
- Reference date: February 2026.