Advanced X-rays techniques for research-oriented high-resolution imaging of articular cartilage: a scoping review

TL;DR

This review explores advanced X-ray imaging techniques, including spectral and phase-contrast methods, for high-resolution, non-destructive analysis of articular cartilage's structure and mechanics, highlighting their benefits and limitations.

Contribution

It provides a comprehensive catalog of advanced X-ray techniques applied to articular cartilage imaging, emphasizing their potential for rheologic research.

Findings

Spectral techniques improve tissue discrimination.

Phase-contrast imaging reveals detailed cartilage structures.

Dark-field imaging relates to sub-pixel tissue features.

Abstract

Articular cartilage is a musculoskeletal soft tissue renowned for its unique mechanical properties. Understanding both its hierarchical structure and the interplay between its constituents could shed light on the mechanical competence of the tissue. Therefore, rheologic approaches based on high-resolution non-destructive imaging techniques are desired. In this context, X-ray imaging could ideally accomplish this task. Nevertheless, the nature of articular cartilage translates into poor contrast using conventional absorption modality. To overcome this limitation, several approaches can be embraced. X-ray visibility of articular cartilage can be increased with the use of radiopaque contrast agents. Therefore, further discrimination of structures could be provided by spectral techniques, pivoting on either multi-energy acquisitions or photon-counting technology. Alternatively, phase-contrast techniques unveil details typically undetected with conventional approaches. Phase-contrast imaging, based on the intrinsic decrement in the refractive index of the tissue, can be achieved with different configurations and implementations, including distinct X-ray sources and optical elements. Additionally, some phase-contrast techniques retrieve the small-angle scattering-based dark-field signal, relatable to sub-pixel structures. This scoping review aims to catalogue the application of these advanced X-ray techniques to articular cartilage imaging, following PRISMA guidelines. It discusses their advantages, limitations, and includes an overview of rheologic applications to articular cartilage.