Nanoscale x-ray holotomography of human brain tissue with phase retrieval based on multienergy recordings

Abstract

X-ray cone-beam holotomography of unstained tissue from the human central nervous system reveals details down to subcellular length scales. This visualization of variations in the electron density of the sample is based on phase-contrast techniques using intensities formed by self-interference of the beam between object and detector. Phase retrieval inverts diffraction and overcomes the phase problem by constraints such as several measurements at different Fresnel numbers for a single projection. Therefore, the object-to-detector distance (defocus) can be varied. However, for cone-beam geometry, changing defocus changes magnification, which can be problematic in view of image processing and resolution. Alternatively, the photon energy can be altered (multi-E). Far from absorption edges, multi-E data yield the wavelength-independent electron density. We present the multi-E holotomography at the Göttingen Instrument for Nano-Imaging with X-Rays (GINIX) setup of the P10 beamline at Deutsches Elektronen-Synchrotron. The instrument is based on a combined optics of elliptical mirrors and an x-ray waveguide positioned in the focal plane for further coherence, spatial filtering, and high numerical aperture. Previous results showed the suitability of this instrument for nanoscale tomography of unstained brain tissue. We demonstrate that upon energy variation, the focal spot is stable enough for imaging. To this end, a doublecrystal monochromator and automated alignment routines are required. Three tomograms of human brain tissue were recorded and jointly analyzed using phase retrieval based on the contrast transfer function formalism generalized to multiple photon energies. Variations of the electron density of the sample are successfully reconstructed. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Advancing the Characterization of Neuronal Cyto-Architecture by X-ray Phase-Contrast Tomography

“…Since 𝛿 𝐸 ∝ 𝐸 −2 and 𝛽 𝐸 ∝ 𝐸 −4 , an object can be sampled with relatively low 𝐸 and close to absorption edges to exploit 𝛽 𝐸 [106], or with increased 𝐸 to elevate the relative amount of phase shift 𝛿 𝐸 compared to X-ray absorption 𝛽 𝐸 [154,180]. Apart from the probe energy, X-ray interaction can be further directed by the choice of sample material (cf.…”

“…Also, multi-defocus reconstructions can flaw image quality due to rescaling and registration of the datasets. Multi-energy reconstruction schemes address this issue and retrieve more quantitative electron-density maps, and induce a variation in Fresnel numbers by changing the energy instead of the propagation distance [11,111,154]. In order to access the 2d-map (𝛿 𝐸 ,𝛽 𝐸 ) of an object, spectral methods can also rely on energy-selective detectors.…”

Simple accurate model‐based phase diversity phase retrieval algorithm for wavefront sensing in high‐resolution optical imaging systems

“…In the field of modern advanced optical imaging, wavefront detection is essential for high‐resolution imaging systems design. Phase retrieval [1] has become an important wavefront sensing technique for high‐resolution optical imaging systems [2, 3], which is already used in many advanced imaging systems, such as large aperture high‐resolution space telescope [4–6], optical microscopes [7, 8], X‐ray imaging [9–11], extreme ultraviolet lithography [12], etc. In the field of wavefront sensing, it is well‐known for its very successful application to Hubble space telescope in aberration correction on‐orbit [13].…”

Porous Catalyst Characterization Using X-ray Nano Tomography and Pore Network Modeling

“…X-ray holotomography is a powerful full-field phase-contrast imaging technique, which works based on the phase shift induced by the object. Unlike absorption techniques, holotomography is a suitable imaging tool with a variety of applications for the characterization of materials with low atomic number ('soft' materials) such as human brain tissue [126,127] , the carbon binder domain in Li-ion electrodes [128] , polymethacrylate surfaces [129] , and catalysts [130] .…”

“…As an example for synchrotron-radiation based X-ray holotomography a schematic of the holotomography experimental setup installed at the P10 beamline of the PETRAIII storage ring at the Deutsches Elektronen-Synchrotron (DESY, Hamburg) can be seen in Figure 1.13 [126] . The X-ray beam passes through an undulator which makes the radiation essentially (transversely) coherent.…”