Resolving the resolution-contrast conflict in x-ray phase-contrast tomography via physics-constrained wavelet fusion
Phys. Rev. Applied 25, 024027 – Published 9 February, 2026
DOI: https://doi.org/10.1103/5561-1vzc
Abstract
Phase-contrast x-ray imaging overcomes low contrast in lightweight materials but suffers from an inherent tradeoff between spatial resolution (SR) and contrast-to-noise ratio (CNR). We resolve this conflict through a physics-constrained wavelet fusion framework. By integrating high-SR direct reconstruction and high-CNR phase retrieval, our method leverages single-level Sym4 wavelet decomposition to separate low-frequency contrast (governed by refractive index gradients) and high-frequency edges (dominated by Fresnel diffraction). The compact support and near-symmetry of Sym4 align with the spatial scales of x-ray propagation at 20 cm, minimizing spectral leakage while suppressing artifacts. For porous polyether ether ketone (PEEK), fused images achieve SR of 7.27 µm (140% enhancement over phase retrieval) and CNR of 8.33 (20.8× improvement over direct reconstruction). Validation on ordinary Portland cement achieves an SR of 10.81 µm and a CNR of 11.48, outperforming traditional Fourier fusion. This approach demonstrates artifact-free visualization of sub-10-µm pore networks, providing a robust pathway for high-fidelity nondestructive testing of lightweight materials in material science and biomedical diagnostics.
