Technical note: Cartilage imaging with sub‐cellular resolution using a laboratory‐based phase‐contrast x‐ray microscope.

Background: Microscopic imaging of cartilage is a key tool for the study and development of treatments for osteoarthritis. When cellular and sub‐cellular resolution is required, histology remains the gold standard approach, albeit limited by the lack of volumetric information as well as by processing artifacts. Cartilage imaging with the sub‐cellular resolution has only been demonstrated in the synchrotron environment. Purpose: To provide a proof‐of‐concept demonstration of the capability of a laboratory‐based x‐ray phase‐contrast microscope to resolve sub‐cellular features in a cartilage sample. Methods: This work is based on a laboratory‐based x‐ray microscope using intensity‐modulation masks. The structured nature of the beam, resulting from the mask apertures, allows the retrieval of three contrast channels, namely, transmission, refraction and dark‐field, with resolution depending only on the mask aperture width. An ex vivo equine cartilage sample was imaged with the x‐ray microscope and results were validated with synchrotron tomography and histology. Results: Individual chondrocytes, that is, cells responsible for cartilage formation, could be detected with the laboratory‐based microscope. The complementarity of the three retrieved contrast channels allowed the detection of sub‐cellular features in the chondrocytes. Conclusions: We provide the first proof‐of‐concept of imaging cartilage tissue with sub‐cellular resolution using a laboratory‐based x‐ray microscope. [ABSTRACT FROM AUTHOR]