Understanding the biomechanics of the human middle ear remains a challenge, primarily due to the auditory ossicles’ size, its location in the temporal bone, and subtle movements. In a recent study, dynamic synchrotron-based x-ray microtomography has been used on acoustically stimulated intact human ears, allowing the three-dimensional visualization of the ossicular chain in intact human ears for the first time. The implementation of a dedicated analysis pipeline has demonstrated the ability to resolve fast micromotions at 128Hz for two acoustic stimuli (110 and 120dB Sound Pressure Level (SPL)) on fresh-frozen human temporal bones. Measuring at lower sound pressure levels is challenging, because the ossicular vibrations become smaller, and the spatial resolution limit of the current detection system is reached. Increasing the spatial resolution without compromising the image quality or the temporal resolution would significantly extend the dynamic imaging capabilities. Here, a comparative study is conducted for a stimulation frequency of 128Hz at 120dB SPL between two synchrotron-based x-ray magnification setups: a 4x high NA macroscope (pixel size 2.75μm) versus a x10 high NA microscope (pixel size 1.1μm) in combination with the GigaFRoST fast read-out detector. It shows that an increase in resolution can indeed improve the detection of the micromovements, at the compromise of a more limited field of view.
Purpose: Synchrotron radiation-based tomography yields microanatomical features in human and animal tissues without physical slicing. Recent advances in instrumentation have made laboratory-based phase tomography feasible. We compared the performance of three cutting-edge laboratory systems benchmarked by synchrotron radiation-based tomography for three specimens. As an additional criterion, the user-friendliness of the three microtomography systems was considered.
Approach: The three tomography systems—SkyScan 2214 (Bruker-microCT, Kontich, Belgium), Exciscope prototype (Stockholm, Sweden), and Xradia 620 Versa (Zeiss, Oberkochen, Germany)—were given 36 h to measure three medically relevant specimens, namely, zebrafish larva, archaeological human tooth, and porcine nerve. The obtained datasets were registered to the benchmark synchrotron radiation-based tomography from the same specimens and selected ones to the SkyScan 1275 and phoenix nanotom m® laboratory systems to characterize development over the last decade.
Results: Next-generation laboratory-based microtomography almost reached the quality achieved by synchrotron-radiation facilities with respect to spatial and density resolution, as indicated by the visualization of the medically relevant microanatomical features. The SkyScan 2214 system and the Exciscope prototype demonstrated the complementarity of phase information by imaging the eyes of the zebrafish larva. The 3-μm thin annual layers in the tooth cementum were identified using Xradia 620 Versa.
Conclusions: SkyScan 2214 was the simplest system and was well-suited to visualizing the wealth of anatomical features in the zebrafish larva. Data from the Exciscope prototype with the high photon flux from the liquid metal source showed the spiral nature of the myelin sheaths in the porcine nerve. Xradia 620 Versa, with detector optics as typically installed for synchrotron tomography beamlines, enabled the three-dimensional visualization of the zebrafish larva with comparable quality to the synchrotron data and the annual layers in the tooth cementum.
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