Berlin 2015 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

BP: Fachverband Biologische Physik

BP 13: Posters: Imaging and Superresolution Optical Microscopy

BP 13.3: Poster

Monday, March 16, 2015, 17:30–19:30, Poster A

X-ray waveguide optics for nanoscale phase contrast tomography — •Martin Krenkel¹, Andrea Markus², Matthias Bartels¹, Christian Dullin², Frauke Alves², and Tim Salditt¹ — ¹Institute for x-ray physics, University Göttingen, Germany — ²University Medical Center, Göttingen, Germany

We use propagation based hard x-ray phase contrast tomography to explore the three dimensional structure of soft biological tissues from the organ down to sub-cellular level. As in classical absorption tomography nano-scale structures only barely absorb the radiation, the much stronger phase shift can be used to enhance the contrast.

To reduce beam inhomogeneities and to fulfill the theoretical assumptions needed for proper reconstruction, we use a divergent x-ray waveguide beam geometry at the synchrotron. Thus, the magnification can be easily tuned by placing the sample at different defocus distances. Due to the small Fresnel numbers in this geometry the measured images are of holographic nature which poses a challenge in phase retrieval. With nearly mono modal x-ray beams resolutions down to 23 nm are achieved. We demonstrate this technique on soft hydrated mouse lung tissue yielding 3D reconstructions for a large field of view and region of interest zoom tomography. To further improve the imaging scheme, we develop new reconstruction algorithms that impose minimal restrictions to the objects, based on an optimized measurements or on using an intrinsic consistency constraint of different tomographic projections.