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International Conference on Biofabrication 2023, September 17th -20th 2023, Saskatoon, Canada Tissue Scaffolds Characterization Using Synchrotron Radiation Micro-Computed Tomography with Helical Acquisition Mode Xiaoman Duan1, Xiao Fan Ding1, Naitao Li1, Ning Zhu1, 2, 3, Xiongbiao Chen1, 4 1Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada. 2Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada 3Canadian Light Source, Saskatoon, S7N 2V3, SK, Canada 4Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada Keywords — Tissue engineering, Hydrogel scaffold, Characterization, Micro-computed tomography. INTRODUCTION In the field of tissue engineering, hydrogel scaffolds have gained significant attention due to their unique properties, due to their unique properties. Accurate imaging techniques are essential for studying the internal structure and properties of these scaffolds. Hydrogel scaffolds have very low density and synchrotron radiation micro-computed tomography (SRµCT) shows high contrast with three-dimensional and noninvasive characterization [1]. Despite many advantages, SR-µCT image quality for hydrogel still needs to be improved due to common ring artifacts resulted from systematic errors or defects on the scintillator, monochromator, or filters. Such artifacts usually reduce the accuracy when visualizing and charactering samples. Methods have been developed to reduce the ring artifacts, e.g., low-pass filtering algorithm, but these approaches suffer from limitations. This work integrates SRµCT with the helical acquisition mode (SR-µHCT) to avoid the ring artifacts issues. SR-µHCT involves two motions, a horizontal rotation and a vertical motion which can spread the intensity of ring artifacts over larger regions in the vertical direction, therefore reducing the effects of artifacts. MATERIALS AND METHODS 4% w/v alginate were printed to scaffolds (dimension: 2 × 2 × 10 mm3) with the needle’s diameter of 100 μm. After 15minute cross-linking, the alginate scaffolds were inserted into PCL tubes which can provide mechanical support [2]. The assembled conduits later were implanted into injured sciatic nerve of Sprague−Dawley rats. Euthanasia was conducted 2 days after surgery and the whole hindlimb was collected and was fixed with formalin for imaging (ex vivo). The SR-µHCT imaging were performed at the BMIT-ID beamline, Canadian Light Source (CLS), Canada. All scans were performed at sample-to-detector distance of 1.5 m, photon energy of 30 keV, helical pitch of 1.5, and the pixel size of 13 µm. RESULTS AND DISCUSSION Fig. 1 shows image quality comparisons of ex vivo scaffolds sample with SR-µCT and SR-µHCT. While SR-µCT exhibits adequate image contrast, it is susceptible to ring artifacts that affect the overall quality. Although these artifacts can be mitigated using a low-pass filtering method, it leads to the introduction of additional ring-like shadows. On the other hand, SR-µHCT effectively minimizes ring artifacts without introducing any further distortions or artifacts. Quantitative evaluation index, contrast-to-noise ratio (CNR) and signalto-noise ratio (SNR) were also measured. These results illustrate a higher characterization accuracy of SR-µHCT compared with SR-µCT, which is essential for following quantitative analysis, e.g., segmentation. Fig. 1 Ex vivo hydrogel scaffolds imaging with SR-µCT and SR-µHCT; (A1-C1) SR-µCT image, SR-µCT image processed by a ring artifacts removal algorithm, and SR-µHCT image. (A2-C2) Corresponding enlarged regions of interest at positions indicated by yellow rectangular. ACKNOWLEDGEMENTS This work is supported by Natural Sciences and Engineering Research Council of Canada (Grant numbers: RGPIN 06007-2019 and RGPIN 06396-2019). REFERENCES [1] X. Duan et al., Tissue Engineering Part C: Methods, vol. 27, no. 11, pp. 573-588, 2021. [2] L. Ning et al., ACS Appl. Mater. Interfaces, vol. 13, no. 22, pp. 25611-25623, 2021.
