Nowadays, thanks to the high brilliance available at modern, third generation synchrotron facilities and recent developments in detector technology, it is possible to record volumetric information at the micrometer scale within few minutes. High signal-to-noise ratio, quantitative information on very complex structures like the brain micro vessel architecture, lung airways or fuel cells can be obtained thanks to the combination of dedicated sample preparation protocols, in-situ acquisition schemes and cutting-edge imaging instruments.

The use of conventional absorption-based X-ray imaging can become limited for samples showing only weak attenuation contrast. However, it is well known, that a wide range of samples studied in biology and materials science can induce significant phase shifts of the X-ray beam. Professor Marco will report on recent experiments carried out at the TOMCAT beamline of the Swiss Light Source where synchrotron-based tomographic microscopy has been successfully used to obtain fundamental information on preliminary models for cerebral fluid flow, to provide an accurate mesh for 3D finite-element simulation of the alveolar structure of the pulmonary acinus and to investigate the complex functional mechanism of fuel cells. The TOMCAT beamline is equipped with cutting edge instrumentation for phase contrast imaging. For moderate spatial resolution (5-10 microns) and high sensitivity (up to 1 mg/cm3) we implemented a highly optimized grating-based Talbot interferometer. Such device has limited requirements on monochromaticity and on spatial coherence, which get though more stringent as high sensitivity and therefore larger fractional Talbot distances are required. These characteristics, combined with the fact that such instrument is particularly sensitive to shallow phase gradients, makes it an ideal technique for soft tissue studies in the fields of medical and biological imaging. For intermediate resolutions (0.5-5 microns) and high temporal resolution (1 Hz-tomography) we are using a modified transport of intensity method which allows tomographic investigations of poorly absorbing materials within a few seconds. For imaging at the nano scale (0.1 microns resolution), synchrotron-based full-field tomographic microscopy established itself as an ideal tool for non-invasive investigations. We implemented an X-ray, full field microscope with tomographic capabilities operating at 10 keV and with a 3D isotropic resolution of 144 nm. Custom optical components including a beamshaping condenser and phase-shifting dot arrays were used to obtain an ideal, aperture-matched sample illumination and very sensitive phase contrast imaging. Due to the use of broad-band radiation, tomographic investigations can be performed within few minutes and we could show that such an instrument can be successfully used for the non-destructive, volumetric investigation of single, non-fixed, unstained cells. In my presentation I will explain the technical solutions adopted for the different imaging configuration and show some of the related biomedical application.

 

Prof. Dr. Marco Stampanoni studied physics at the Swiss Federal Institute of Technology Zürich (ETHZ) and obtained his Master Degree in Nov. 1998. He enrolled in a PhD program at the Institute for Biomedical Engineering (ETHZ) under the supervision of Prof. P. Rüegsegger, a pioneer in the development of quantitative computed X-ray tomography. At the same time, he started a Master of Advanced Studies in Medical Physics, successfully concluded in October 2000. Stampanoni has been working in the field of tomographic microscopy since the beginning of his scientific career. The subject of his physics PhD – obtained at the ETH Zürich on Feb. 2003 – was the development of a novel approach towards micrometer resolution X-ray computed tomography. He realized a system, dubbed “Bragg Magnifier”, which showed sub micrometer spatial resolution and high efficiency. In addition, Stampanoni contributed massively to the successful realization of the X-ray Tomographic Microscopy (XTM) endstation at the Materials Science (MS) beamline of the Swiss Light Source (SLS) at the Paul Scherrer Institut (PSI) in Villigen, Switzerland. His PhD was awarded with the ETH Medal in 2003. In 2004 he was appointed beamline scientist and initiated the TOMCAT project, a beamline for Tomographic Microscopy and Coherent rAdiology experiments at the Swiss Light Source. Stampanoni is heading the X-ray Tomographic Microscopy Group of the Swiss Light Source since 2005. In 2008 Stampanoni has been appointed Assistant Professor for X-ray Microscopy at the Department for Information Technology and Electrical Engineering (D-ITET) of ETH Zürich. His professorship is affiliated with the Institute of Biomedical Engineering (IBT) of the University and ETH Zürich. He is still the Head of the X-ray Tomographic Microscopy Group of the Swiss Light Source at the Paul Scherrer Institute.  Together with his group, he is working on novel X-ray based tomographic instruments and methods for non-invasive 3D investigations of biosamples at the micron and nano scale. He is interested in developing and optimizing imaging modalities (absorption, phase and darkfield contrast), tomographic reconstruction algorithms as well as imaging instruments (microscopes and nanoscopes).  He is giving three lectures at Master level entitled “Micro and Nano-Tomography of Biological Tissues”, “Elements of Microscopy” and “Research Topics in Biomedical Engineering”. He presently acts as a consultant in technical panels worldwide.