In Vitro Preparation of Actively Maturing Bovine Articular Cartilage Explants for X-Ray Phase Contrast Imaging.

Understanding the mechanisms that underpin post-natal maturation of articular cartilage is of crucial importance for designing the next generation of tissue engineering strategies and potentially repairing diseased or damaged cartilage. In general, postnatal maturation of the articular cartilage, which is a wholesale change in collagen structure and function of the tissue to accommodate growth of the organism, occurs over a timescale ranging from months to years. Conversely dissolution of the structural organization of the cartilage that also occurs over long timescales is the hallmark of tissue degeneration. Our ability to study these biological processes in detail have been enhanced by the findings that growth factors can induce precocious in vitro maturation of immature articular cartilage. The developmental and disease related changes that occur in the joint involve bone and cartilage and an ability to co-image these tissues would significantly increase our understanding of their intertwined roles. The simultaneous visualization of soft tissue, cartilage and bone changes is nowadays a challenge to overcome for conventional preclinical imaging modalities used for the joint disease follow-up. Three-dimensional X-ray Phase-Contrast Imaging methods (PCI) have been under perpetual developments for 20 years due to high performance for imaging low density objects and their ability to provide additional information compared to conventional X-ray imaging. In this protocol we detail the procedure used in our experiments from biopsy of the cartilage, generation of in vitro matured cartilage to data analysis of image collected using X-ray phase contrast imaging.

Calcified cartilage revealed in whole joint by X-ray phase contrast imaging.

Objective: X-ray Phase Contrast Imaging (PCI) is an emerging modality that will be in the next few years available in a wider range of preclinical set-ups. In this study, we compare this imaging technique with conventional preclinical modalities in an osteoarthritis mouse model. Method: Phase contrast technique was performed on 6 post-mortem, monoiodoacetate-induced osteoarthritis knees and 6 control knees. The mice knees were then imaged using magnetic resonance imaging and conventional micro computed tomography. Examples of imaging surrogate markers are reported: local distances within the articular space, cartilage surface roughness, calcified cartilage thickness, number, volume and locations of osteophytes. Results: Thanks to PCI, we can show in 3D calcified cartilage without contrast agent by a non-invasive technique. The phase contrast images reveal more details than conventional imaging techniques, especially at smaller scales, with for instance a higher number of micro-calcifications detected (57, 314 and 329 for MRI, conventional micro-CT and phase contrast imaging respectively). Calcified cartilage thickness was measured with a significant difference (p â€‹< â€‹0.01) between the control (23.4 â€‹± â€‹17.2 â€‹µm) and the osteoarthritis induced animal (46.9 â€‹± â€‹19.0 â€‹µm). Conclusions: X-ray phase contrast imaging outperforms the conventional imaging modalities for assessing the different tissue types (soft and hard). This new imaging modality seems to bring new relevant surrogate markers for following-up small animal models even for low-grade osteoarthritis.

Comparison of X-ray speckle-based imaging deflection retrieval algorithms for the optimization of radiation dose.

X-ray phase contrast imaging can provide improved or complementary information to traditional attenuation-based X-ray imaging, making the field a vast and rapidly evolving research subject. X-ray speckle-based imaging (SBI) is one phase-contrast imaging approach that has shown significant potential in providing both high sensitivity and high resolution while using a very simple experimental setup. With the aim of transferring such phase-contrast-based imaging techniques from synchrotron to laboratory X-ray sources, the issue of the deposited radiation dose still remains to be addressed. In this work, we experimentally and quantitatively compare the results from three different SBI phase retrieval algorithms using both phantoms and biological samples in order to infer the optimal configuration. The results obtained using a synchrotron beam suggest that the technique based on optical flow conservation achieves the most accurate retrieval from the lowest number of sample exposures. This constitutes an important step toward the possibility of transferring SBI into the clinic.

X-ray Phase Contrast osteo-articular imaging: a pilot study on cadaveric human hands.

X-ray Phase Contrast Imaging (PCI) is an emerging modality whose availability in clinics for mammography and lung imaging is expected to materialize within the coming years. In this study, we evaluate the PCI Computed Tomography (PCI-CT) performances with respect to current conventional imaging modalities in the context of osteo-articular disorders diagnosis. X-ray PCI-CT was performed on 3 cadaveric human hands and wrists using a synchrotron beam. Conventional CT, MRI and Ultrasound were also performed on these three samples using routine procedures as well as research protocols. Six radiologists and rheumatologists independently evaluated qualitatively and semi quantitatively the 3D images' quality. Medical interpretations were also made from the images. PCI-CT allows the simultaneous visualization of both the high absorbing and the softer tissues. The 6 reader evaluations characterized PCI-CT as a visualization tool with improved performances for all tissue types (significant p-values), which provides sharper outlines and clearer internal structures than images obtained using conventional modalities. The PCI-CT images contain overall more information, especially at smaller scales with for instance more visible micro-calcifications in our chondrocalcinosis case. Despite a reduced number of samples used, this pilot study highlights the possible medical benefits of PCI for osteo-articular disorders evaluation. Although PCI-CT is not yet available in hospitals, the improved visualization capabilities demonstrated so far and the enhanced tissue measurement quality let suggest strong diagnosis benefits for rheumatology in case of a widespread application of PCI.