ISO 19232-5:2018

Overview

ISO 19232-5:2018 - Non‑destructive testing (NDT) - Image quality of radiographs - Part 5 specifies a standardized method for determining total image unsharpness and basic spatial resolution of radiographs and radioscopic images using duplex wire‑type image quality indicators (IQIs). The standard defines IQI construction, marking and conformity requirements, and practical evaluation procedures for both film and digital detectors.

Key topics and requirements

• Duplex wire‑type IQI design: A series of up to 13 duplex wire pairs mounted in a rigid transparent holder. Wires D1–D3 are tungsten; remaining elements are platinum. Wire diameter (d) equals spacing between wires.
• Measurement concepts:
  • Total image unsharpness (UT) is given by 2·d.
  • Basic spatial resolution (SRb) equals half of the measured unsharpness.
  • Linepair/mm value is 1/(2·d).
• Wire sizes: Duplex elements span fine to coarse pairs (e.g., wire diameters/spacing from ~0.05 mm to ~0.80 mm), enabling resolution readings up to ~10 lp/mm for the finest pairs (values per Table 1 in the standard).
• Use limits by X‑ray tube voltage:
  • IQIs with up to 13 wire pairs effective up to 600 kV.
  • IQIs with more than 13 wire pairs intended for tube voltages <225 kV. Results may be unsatisfactory in the megavolt range.
• Evaluation methods:
  • Visual evaluation on film/monitor (magnification up to 4×; use >2× lens for very fine pairs).
  • Digital evaluation with profile function: determine first duplex pair with <20% modulation depth in a linearized profile. IQI should be placed at ~2°–5° to pixel grid to reduce aliasing. Profile should integrate ~30–60% of wire length with a minimum 11‑pixel width.
  • Interpolation (iUT / iSRb): use profile interpolation to obtain more precise 20% modulation values.
• Traceability and marking: IQIs must be marked (e.g., “ISO 19232‑5” + serial number) and supplied with a declaration of conformity per ISO/IEC 17050‑1.

Applications and users

• Who uses it: NDT technicians, radiographers, QA/QC engineers, inspection authorities, and manufacturers of radiography equipment and digital detectors.
• Practical uses:
  • Routine image quality acceptance testing of film and digital radiography systems.
  • Detector characterization (place IQI directly on detector to measure detector unsharpness/SRb).
  • Defining minimum image quality for production radiographs and compliance with inspection procedures.

Related standards

• ISO 19232 series (other parts cover different IQI types and image quality measures)
• ISO 5576 (NDT radiology vocabulary)
• ISO/IEC 17050‑1 (supplier’s declaration of conformity)

Keywords: ISO 19232-5:2018, duplex wire-type IQI, image unsharpness, basic spatial resolution, radiograph image quality, NDT, digital radiography, linepair/mm, detector SRb.