A team led by Professor Ian Robinson of the London Centre for Nanotechnology has this month been awarded an EPSRC grant of £1.4M. The grant will fund researchers in the new national Research Complex at Harwell to investigate "Phase modulation technology for X-ray imaging" - developing new methods of three dimensional imaging with both visible light and X-rays. The team members include Dr. Sandro Olivo (Medical Physics and Bioengineering, UCL), Professor Christoph Rau (Diamond Light Source) and Professor John Rodenberg (Electrical Engineering, University of Sheffield).
The research enabled by the new methods will see wide applications in visualising the details of processes involved in biological, medical and materials science. This includes, amongst others, the orientation of magnetic domains, changes of phase such as solidification and crystallization, cracks and modifications occurring after the processing of materials. The flexibility of the methods will enable studies of similar processes to be undertaken as they occur, as well as the imaging of samples requiring sophisticated manipulation, housing and/or extreme pressure/temperature conditions. The project focuses on enhancements achievable by the technique of phase modulation, either by improving image contrast or by broadening the range of accessible samples by allowing them to be imaged (phased) in the first place.
An example of one of the new Modulation methods which will be introduced for imaging biological tissues is called "Phase Grating Coherent Diffraction Imaging". This has the potential to achieve much higher resolution than before. The figure below illustrates Coherent X-ray Diffraction from the protein collagen within an entire rat-tail tendon, illuminated with a 10-micron X-ray beam. It shows a characteristic speckle pattern at the position of the diffraction of the 67nm repeat spacing of its collagen component. When mixed with the modulation signal from an artificially engineered grating, with a spacing matched to the repeat distance of the protein, interference of the two (coherent) diffraction patterns takes place. The modulation information should allow the diffraction pattern to be inverted to an image of the collagen.
Top: Coherent diffraction pattern from an aligned rat-tail tendon. Bottom: same with superposition of the diffraction pattern of a grating designed in LCN and created using e-beam lithography.
The team brings together a range of expertise. Professor Robinson is an expert in coherent X-ray techniques. Dr. Olivo is the inventor of the coded-aperture phase contrast method, and one of the designers of the station at the ELETTRA synchrotron in Trieste dedicated to in-vivo phase-contrast mammography . Professor Rau is the Principal Beamline Scientist of the "Coherence and Imaging" beamline of Diamond where the x-ray experimental part of the proposed research will be based. He is a pioneer in phase-contrast tomographic imaging of biological tissues, applied most recently to the cochlea. Professor Rodenberg is the inventor of the ptychography imaging algorithm which will be developed within the collaboration.
The Research Complex at Harwell is a revolutionary new idea of hosting science in a "research hotel" located at a national laboratory with ready access to the UK's leading large scale facilities. The team will occupy space for a fixed term five-year contract and expect to make breakthroughs in a number of new methods on imaging. Six agencies (MRC, BBSRC, EPSRC, STFC, Diamond and the Welcome Trust) are pooling their resources to make the idea work. They have teamed up together to construct a research laboratory capable of housing 200 scientists on the Harwell-Oxford site, expecting that the mix of physical and biological scientists there will breed strong interdisciplinary collaborations and exciting new ideas.