Nondestructive testing of defects at pixel level with move contrast X-ray imaging

X-ray imaging is broadly applied for defect detection in industry and research. However, traditional X-ray imaging methods struggle to achieve high sensitivity for pixel-level defects (1–3 pixels) in noisy or scattering-dominated environments, such as metal workpieces or thick low-Z materials. To address this, we introduce move contrast X-ray imaging (MCXI), which leverages relative motion between the sample and imaging system to suppress noise and enhance the sensitivity of weak signal detection in complex backgrounds. MCXI has been successfully applied in fields such as biomedical imaging and high-resolution material studies, demonstrating significant noise resistance and sensitivity improvements. This paper extends MCXI to the testing of defects in static samples, aiming to solve the challenges of detecting pixel-level in high-noise and complex backgrounds. Numerical simulations demonstrate MCXI's capability for single-pixel defect detection. Synchrotron radiation experiments validate this technique through quantitative characterization of 1.54-pixel defects (1-μm polystyrene spheres) in low-contrast polyvinyl chloride (PVC) samples, achieving a CNR of 26.12 - representing a 14.04 × improvement over direct projection imaging. The method's industrial applicability is demonstrated through alloy steel pipe testing with 81.2 μm defects (8.12 pixels), where MCXI achieves a CNR of 15.16 (8.1 × enhancement) using laboratory-based X-ray systems. MCXI's seamless integration with both synchrotron facilities and industrial X-ray machines, combined with its noise-resistant characteristics, establishes a universal solution for high-sensitivity nondestructive testing in challenging environments with strong scattering and complex backgrounds.