Schaeper Jannis Justus, Liberman Michael Charles, Salditt Tim
University of Göttingen, Institute for X-ray Physics, Göttingen, Germany.
University of Göttingen, Cluster of Excellence "Multiscale Bioimaging: Molecular Machines to Networks of Excitable Cells," Göttingen, Germany.
J Med Imaging (Bellingham). 2023 Sep;10(5):053501. doi: 10.1117/1.JMI.10.5.053501. Epub 2023 Sep 25.
Assessing the complex three-dimensional (3D) structure of the cochlea is crucial to understanding the fundamental aspects of signal transduction in the inner ear and is a prerequisite for the development of novel cochlear implants. X-ray phase-contrast computed tomography offers destruction-free 3D imaging with little sample preparation, thus preserving the delicate structure of the cochlea. The use of heavy metal stains enables higher contrast and resolution and facilitates segmentation of the cochlea.
For μ-CT of small animal and human cochlea, we explore the heavy metal osmium tetroxide (OTO) as a radiocontrast agent and delineate laboratory from synchrotron CT. We investigate how phase retrieval can be used to improve the image quality of the reconstructions, both for stained and unstained specimens.
Image contrast for soft tissue in an aqueous solution is insufficient under the in-house conditions, whereas the OTO stain increases contrast for lipid-rich tissue components, such as the myelin sheaths in nervous tissue, enabling contrast-based rendering of the different components of the auditory nervous system. The overall morphology of the cochlea with the three scalae and membranes is very well represented. Further, the image quality of the reconstructions improves significantly when a phase retrieval scheme is used, which is also suitable for non-ideal laboratory settings. With highly brilliant synchrotron radiation (SR), we achieve high contrast for unstained whole cochleae at the cellular level.
The OTO stain is suitable for 3D imaging of small animal and human cochlea with laboratory , and relevant pathologies, such as a loss of sensory cells and neurons, can be visualized. With SR and optimized phase retrieval, the cellular level can be reached even for unstained samples in aqueous solution, as demonstrated by the high visibility of single hair cells and spiral ganglion neurons.
评估耳蜗复杂的三维（3D）结构对于理解内耳信号转导的基本方面至关重要，并且是新型人工耳蜗开发的先决条件。X射线相衬计算机断层扫描无需对样品进行大量制备即可提供无损3D成像，从而保留耳蜗的精细结构。使用重金属染色剂可实现更高的对比度和分辨率，并有助于耳蜗的分割。
对于小动物和人类耳蜗的μ-CT，我们探索将重金属四氧化锇（OTO）用作放射造影剂，并区分实验室CT和同步加速器CT。我们研究了如何使用相位恢复来提高染色和未染色标本重建的图像质量。
在实验室条件下，水溶液中软组织的图像对比度不足，而OTO染色增加了富含脂质的组织成分（如神经组织中的髓鞘）的对比度，从而能够基于对比度对听觉神经系统的不同成分进行渲染。具有三个蜗管和膜的耳蜗的整体形态得到了很好的呈现。此外，当使用相位恢复方案时，重建的图像质量会显著提高，该方案也适用于非理想的实验室设置。利用高亮度的同步加速器辐射（SR），我们在细胞水平上实现了未染色的整个耳蜗的高对比度。
OTO染色适用于实验室CT对小动物和人类耳蜗进行3D成像，并且可以可视化相关病理情况，如感觉细胞和神经元的丧失。如单个毛细胞和螺旋神经节神经元的高可见度所示，通过SR和优化的相位恢复，即使对于水溶液中的未染色样品也可以达到细胞水平。
