A Contour-Constrained Heterogeneity Significance-Based 3-D Muon Imaging for Deteriorated Cultural Relics

Cultural heritage artifacts are frequently subjected to complex structural degradations, such as delamination, corrosion, and internal cracking. However, conventional detection technologies often struggle to assess these conditions due to limited penetration depth, sensitivity constraints with high-Z materials, and the inability to perform on-site measurements on large-scale objects. Cosmic ray muon imaging offers a deep-penetrating, non-invasive alternative ideal for such scenarios, yet its precision relies heavily on the efficacy of the reconstruction method. To address these challenges, this work proposes the contour-constrained heterogeneity significance (CCHS) method, a novel three-dimensional muon imaging reconstruction framework tailored for accurate internal inspection. Unlike traditional methods, the CCHS method integrates prior contour knowledge with a rotation scheme to effectively mitigate scattering ambiguity and constrain the reconstruction space. Validations through both simulations and field experiments demonstrate the method’s exceptional sensitivity, which successfully resolves fine-scale hierarchical structures with layer thicknesses of 1 cm and density contrasts as low as 0.5 g/cm3. Compared to the conventional method, CCHS yields reconstructions with higher smoothness and consistency, while reducing the required muon statistics by a factor of 100, making it exceptionally well-suited for efficient inspections at various scales. This research establishes muon imaging as a generally applicable tool for heritage preservation and a wide range of non-destructive testing applications.