Overview
ISO 15708-4:2017 - Non-destructive testing - Radiation methods for computed tomography - Part 4: Qualification - provides guidelines to qualify the performance of industrial computed tomography (CT) systems for specific inspection tasks. It applies to computed axial tomography used in non-medical (industrial) imaging and defines consistent CT performance parameter definitions and how they relate to system specifications. The standard excludes translational tomography and tomosynthesis.
Key topics and requirements
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Qualification of inspection
- Distinguishes between defect testing and dimensional testing, requiring task-specific qualification when derived quantities (e.g., pore size, wall thickness) are needed.
- Emphasizes trained personnel and traceable documentation.
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Quality feature definition
- Define test object and test feature attributes: dimensions, material, path length, feature type/size/position/distribution and limiting defect/feature.
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Feature detectability & system parameterization
- Spatial resolution factors: overall image resolution, scan geometry, detector resolution, X‑ray focal spot.
- Contrast resolution factors: detector settings, tube voltage/current.
- Reconstruction/visualization factors: number of projections, CT grey‑value dynamic range, image voxel size (X, Y, Z).
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Verification of suitability
- Use reference samples with natural or synthetic defects, or leverage known sample structures (wires, spheres) when specifications are limited.
- Establish and state the required degree of accuracy, tolerances and limits of detectability.
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Consistency checks and system qualification
- Inspect reconstruction for artifacts, check CT image scale, review sinograms/projection sequences and system status logs.
- Perform component checks (manipulation system, image scale, beam axis perpendicularity, tube focal spot & stability, detector, reconstruction algorithms, visualization tools).
- Archive CT images and test parameters to enable reproducibility.
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Resolution evaluation methods (examples)
- Guidance on acquisition parameters, reference object creation and density resolution measurement methods (high/low energy) and experimental measurement considerations.
Applications - who uses this standard
- NDT engineers, CT technicians, QA managers and inspection service providers who need to demonstrate and document CT system suitability.
- Industries: aerospace, automotive, additive manufacturing, foundries, power generation, and R&D labs that perform industrial CT for defect detection and dimensional metrology.
- CT system manufacturers and integrators for specifying and validating performance against inspection tasks.
Related standards
- ISO 15708-1 - terms and definitions (referenced for vocabulary)
- ISO 15708-2 - operation and interpretation (referenced for system set‑up and image quality parameters)
Keywords: ISO 15708-4:2017, computed tomography qualification, industrial CT, CT performance parameters, non-destructive testing, defect detectability, dimensional testing, CT system validation.
Open preview (PDF)Non-destructive testing — Radiation methods for computed tomography — Part 4: Qualification
