ISO 15708-4:2017

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

• 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.

• Quality feature definition

  • Define test object and test feature attributes: dimensions, material, path length, feature type/size/position/distribution and limiting defect/feature.

• 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).

• 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.

• 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.

• 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.