A letter published in the current issue of Nature describes the use of a ptychographic coherent approach in CT imaging to resolve nanoscale structures. The nano-CT approach, developed by Franz Pfeiffer of Technische Universität München and his team, uses not only X-ray beam intensity of a sample but also beam diffraction to provide additional nanoscale data. Diffraction patterns are then processed by a novel image reconstruction algorithm, generating high-resolution 3D-images. The technique allows the visualization of minute structures, such as osteocyte lacunae and the connecting canaliculi, and promises to advance research in a variety of fields.
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A showcase example of the new technique was the examination of a 25-micrometer, superfine bone specimen of a laboratory mouse – with surprisingly exact results. The so-called phase contrast CT pictures show even smallest variations in the specimen’s bone density with extremely high precision: Cross-sections of cavities where bone cells reside and their roughly 100 nanometer-fine interconnection network are clearly visible.
"Although the new nano-CT procedure does not achieve the spatial resolution currently available in electron microscopy, it can – because of the high penetration of X-rays – generate three-dimensional tomography images of bone samples,” comments Roger Wepf, director of the Electron Microscopy Center of the ETH Zurich (EMEZ). “Furthermore, the new nano-CT procedure stands out with its high precision bone density measurement capacity, which is particularly important in bone research.” This method will open the door to more precise studies on the early phase of osteoporosis, in particular, and evaluation of the therapeutic outcomes of various treatments in clinical studies.
This animation shows the first nano-CT pictures of a bone sample with a diameter of about 25 micrometers. Clearly resolved are the fine, approximately 100-nanometer channels (canaliculi) that make up the interconnective network between the bone cells (osteocytes).
Press release: High-resolution method for computed nano-tomography developed
Letter in Nature: Ptychographic X-ray computed tomography at the nanoscale