Overview
EN ISO 15708-1:2024 - Non-destructive testing - Radiation methods for computed tomography - Part 1: Vocabulary (ISO 15708-1:2024) is the latest, third-edition terminology standard for computed tomography (CT) used in non-destructive testing (NDT). Prepared by ISO/TC 135 in collaboration with CEN/TC 138, this document defines CT-specific and related imaging/radiography terms (e.g., voxel, CT projection, reconstruction) and clarifies discussion points to refocus definitions in the CT context. It supersedes the earlier EN ISO 15708-1 (2019) and replaces ISO 15708-1:2017.
Key topics
The standard provides authoritative definitions and concise explanations for core CT and radiation-imaging concepts, including:
- CT image, CT slice, CT volume, CT grey value - terminology for 2D/3D image data and voxel-level values.
- CT projection, CT scan, CT system - acquisition geometry and system components.
- Scanning modes - cone beam CT, fan beam CT, parallel beam CT (definitions of ray-path geometries).
- Image formation & processing - reconstruction, sinogram, ray path.
- Physical interaction terms - absorption (photoelectric), Compton scattering, X‑ray attenuation, linear attenuation coefficient.
- Image quality effects - artefact, beam hardening, cupping effect, partial volume effect, density resolution.
- Measurement and QC terms - calibration template (phantom), region of interest (ROI), region of interest CT, slice thickness, pixel/voxel.
- Notes describing relationships between terms and corrected definitions (notably terms 3.8, 3.9, 3.20 and 3.27 in this edition).
The document contains no normative references and points users to ISO and IEC terminology databases for related definitions.
Applications
This vocabulary standard supports consistent communication, specification and interpretation across CT-based NDT activities:
- Standardizing terminology in inspection reports, procurement documents and technical specifications.
- Aligning software interfaces, training materials, and acceptance criteria for industrial CT systems.
- Supporting quality assurance, method development and inter-laboratory communication when evaluating CT images, artefacts and measurement results.
- Informing development of procedures for CT-based inspection of additive-manufactured parts, castings, composites, and assemblies where precise vocabulary improves reproducibility.
Who should use this standard
- NDT engineers and technicians working with industrial CT
- Radiography/CT system manufacturers and software developers
- Quality managers, certification bodies and inspectors
- Researchers and trainers involved in CT image analysis and method development
- Standards committees and regulatory bodies harmonizing CT terminology
Related standards
EN ISO 15708-1 is part of the ISO 15708 series on radiation methods for computed tomography. For additional context and related definitions consult the ISO Online Browsing Platform and IEC Electropedia. CEN members are required to implement the EN version as a national standard (endorsement deadline noted in the European foreword).
