Visualizing soft tissue in the mammalian cochlea with coherent hard X-rays

Abstract

This paper concerns an important aspect of current developments in medical and biological imaging: the possibility for imaging soft tissue at relatively high resolution in the micrometer range or better, without tedious and/or entirely destructive sample preparation. Structures with low absorption contrast have been visualized using in-line phase contrast imaging. The experiments have been performed at the Advanced Photon Source, a third generation source of synchrotron radiation. The source provides highly coherent X-ray radiation with high photon flux (>10(14) photons/s) at high photon energies (5-70 keV). Thick gerbil cochlear slices have been imaged and were compared with those obtained by light microscopy. Furthermore, intact gerbil cochleae have been imaged to identify the soft tissue structures involved in the hearing process. The present experimental approach was essential for visualizing the inner ear structures involved in the hearing process in an intact cochlea.

Three-Dimensional Gas Exchange Pathways in Pome Fruit Characterized by Synchrotron X-Ray Computed Tomography

“…In tissues, the structural arrangements of cells create specific pathways for transport of chemical compounds to and from cells. Visualization of these pathways by x-ray microtomography of tissues in their natural state has been difficult, because of the low contrast and limited resolution (Westneat et al, 2003;Kuroki et al, 2004;Kim et al, 2006;Rau et al, 2006;Mendoza et al, 2007). Important features such as small voids between cells, vascular capillaries, or cell walls could therefore not be visualized, rendering incorrect connectivity information.…”

Phase contrast tomography of the mouse cochlea at microfocus x-ray sources

“…Detailed knowledge about the delicate and complex cochlea morphology is necessary to understand malformations caused by genetic defects, improve the treatment of hearing diseases, and optimize the design of cochlear implants. 2,3 Optogenetic stimulation of spiral ganglion neurons (SGNs) using lightgated ion channels is a promising approach to overcome the limited sound frequency resolution of current cochlear implants. 1 In this research, a central challenge is to determine the position and orientation of the light emitter(s) (e.g., an optical fiber) relative to the spiral ganglion.…”

“…Therefore, coherent x-ray methods 8,9,13 exploiting the phase shift induced by the sample are particularly well suited for cochlea imaging, as shown by recent synchrotron studies. 3,14,15 Nevertheless, these studies rely on the (limited) availability of third generation synchrotron facilities, inhibiting a routine use in the laboratory, which is needed for long-term biomedical research. Even though grating-based imaging enables phase contrast with laboratory sources, [18][19][20][21][22] the reported resolution range above 30 lm is not sufficient to identify thin membranes or nerve fibers within the cochlea.…”

“…16 As a result, the obtained data allow automatic histogram-based segmentation between bone and soft tissue, in contrast to previously reported synchrotronbased phase contrast studies of the cochlea which skipped the phase reconstruction step. 3,15 This enables fast and convenient data visualization, which is a key requisite for batch analysis of several cochleae, e.g., as part of a biomedical study.…”

“…Importantly, phase contrast can also be exploited in this geometry, due to the symmetry of z eff with respect to z 1 and z 2 . In fact, the parallel beam geometry employed in most synchrotron phase contrast experiments (from early demonstrations 8,13,23 to recent cochlea studies 3,15 ) corresponds to the limit z 1 ) z 2 . Nonetheless, in contrast to synchrotron instrumentation, for compact microfocus setups z 1 and z 2 can continuously be changed, including an optimal setting with M…”