Research Highlights

Anisotropic X-ray Dark-field Tomography

Conventional X-ray imaging is based on X-rays being absorbed differently by various materials or amounts of material, hence the term absorption contrast. In the same way as visible light, X-rays can also be refracted (enabling phase contrast) or scattered (enabling dark-field contrast), which can be measured using X-ray grating interferometers. A unique property of the dark-field contrast is its directional anisotropy, meaning that the signal changes when a sample is rotated in the plane orthogonal to the incoming X-ray beam. This is due to fibrous microstructures (such as nerve fibers in the brain, or carbon fibers in composite materials) causing scattering orthogonal to the fiber orientation, even though the microstructures themselves are too small to be resolved.

Our research is focusing on deriving suitable forward models for the anisotropic X-ray dark-field contrast, as well as algorithms to solve the resulting inverse problem. In addition, we are investigating practical acquisition strategies to acquire the anisotropic dark-field signal.

Related publications:

  • M. Wieczorek, F.Schaff, C. Jud, D. Pfeiffer, F. Pfeiffer, T. Lasser. Brain Connectivity Exposed by Anisotropic X-ray Dark-field Tomography. Scientific Reports 8, 2018 DOI
  • Y. Sharma, F. Schaff, M. Wieczorek, F. Pfeiffer, T. Lasser. Design of Acquisition Schemes and Setup Geometry for Anisotropic X-ray Dark-Field Tomography (AXDT). Scientific Reports 7, 2017 DOI
  • M. Wieczorek, F. Schaff, F. Pfeiffer, T. Lasser. Anisotropic X-ray Dark-Field Tomography: A Continuous Model and its Discretization. Physical Review Letters 117, 2016 DOI

Light Field Microscopy

Light field imaging is a scanless imaging technique that provides one-shot volumetric information, for example in fluorescent microscopy. It has proven very useful in biologic applications involving fast dynamics, due to its high speed 3D imaging capability. The light field microscope enables scan-less 3D imaging of fluorescent specimens by incorporating an array of micro-lenses into the optical path of a conventional wide-field microscope. Thus, both spatial and directional light field information is captured in a single shot, allowing for subsequent volumetric reconstruction using a wave-based forward model to describe the propagation of light.

Our research is focusing on deriving suitable forward models for light field microscopy, as well as algorithms to solve the resulting inverse problem.

Related publications:

  • A. Stefanoiu, G. Scrofani, G. Saavedra, M. Martinez-Corral, T. Lasser. What about computational super-resolution in fluorescence Fourier light field microscopy? Optics Express 28, 2020 DOI
  • A. Stefanoiu, J. Page, P. Symvoulidis, G. Westmeyer, T. Lasser. Artifact-free deconvolution in light field microscopy. Optics Express 27, 2019 DOI
  • P. Symvoulidis, A. Lauri, A. Stefanoiu, M. Cappetta, S. Schneider, H. Jia, A. Stelzl, M. Koch, C. Perez, A. Myklatun, S. Renninger, A. Chmyrov, T. Lasser, W. Wurst, V. Ntziachristos, G. Westmeyer. NeuBtracker – an imaging platform for interrogating neurobehavioral dynamics in freely behaving fish. Nature Methods 14, 2017 DOI