ASTM E1931-16(2022)

Overview

ASTM E1931-16(2022), Standard Guide for Non-computed X-Ray Compton Scatter Tomography, provides a comprehensive introduction to the method known as Compton Scatter Tomography (CST). Developed by ASTM International, this standard offers guidance on operational capabilities, physics principles, hardware setup, and the advantages and limitations of CST for nondestructive examination (NDE).

CST utilizes the unique physics of X-ray scattering-specifically, Compton scatter-to generate three-dimensional radioscopic images of internal features. Its principal advantage is the ability to examine objects without the need for access to the back side, making it invaluable for components where only one side is accessible. CST is particularly beneficial for imaging low subject contrast materials and offers high-contrast sensitivity and spatial resolution.

Key Topics

• Three-dimensional Imaging with One-side Access

  • CST allows 3D internal imaging without requiring the X-ray beam to entirely penetrate the object or access to its opposite side. This is ideal for inspecting complex parts or installed assets.

• Imaging Low Subject Contrast Materials

  • CST performs well with materials that are difficult to image using conventional radiography, such as plastics, foams, or composites.

• Minimized Surface Feature Influence

  • Images are predominantly influenced by the slice plane, reducing image degradation from features outside that plane.

• Radiation Safety Advantages

  • In thicker or denser objects, the object itself absorbs much of the primary radiation, acting as shielding and thereby reducing the external radiation hazard.

• Limitations

  • Best suited for lower density, reasonably thick materials. For example, typical imaging depths are up to 25 mm in aluminum and 50 mm in some plastics. High-density materials significantly limit penetration depth.
  • The examination volume is relatively small, and imaging large structures requires repositioning, making it more time-intensive.
  • Professional training and standard calibration are critical for proper image interpretation and safety compliance.

Applications

Compton Scatter Tomography is a nondestructive testing method positioned for specific, challenging applications, including:

• Industrial Nondestructive Evaluation

  • Inspecting aerospace composites, plastics, and foams for subsurface defects when access is limited to a single side.
  • Detecting internal voids, delaminations, or low-density inclusions in thick, complex parts.

• Security Screening

  • Screening luggage or cargo where only one-side inspection is feasible.

• Archaeological and Forensic Analysis

  • Non-intrusive examination of delicate artifacts or evidence, especially items that cannot be moved or require preservation.

Note: CST’s effectiveness must be validated for each application in the laboratory setting, as material type, object size, and geometry all influence image quality and suitability.

Related Standards

Professionals working with CST or seeking to implement non-computed X-ray Compton Scatter Tomography should be familiar with related ASTM and international standards, including:

• ASTM E747: Practice for Design, Manufacture and Material Grouping Classification of Wire Image Quality Indicators (IQI) for Radiology
• ASTM E1025: Practice for Design, Manufacture, and Material Grouping Classification of Hole-Type Image Quality Indicators for Radiography
• ASTM E1255: Practice for Radioscopy
• ASTM E1316: Terminology for Nondestructive Examinations
• ASTM E1441: Guide for Computed Tomography (CT)
• ISO 9712: Nondestructive Testing-Qualification and Certification of NDT Personnel
• ANSI/ASNT CP-189: Standard for Qualification and Certification in Nondestructive Testing Personnel

Familiarity with these standards supports consistency, personnel competency, and quality assurance in CST applications.

ASTM E1931-16(2022) provides a foundational framework for organizations looking to leverage non-computed X-ray Compton scatter tomography for advanced, application-specific nondestructive evaluations. Following this standard ensures reliable, safe, and effective deployment of CST technology.