A novel nano-tomography method developed by a team of researchers opens the door to computed tomography examinations of minute structures at nanometer resolutions. The new method makes possible, for example, three-dimensional internal imaging of fragile bone structures. This new technique will facilitate advances in both life sciences and materials sciences.
Osteoporosis, a medical condition in which bones become brittle and fragile from a loss of density, is among the most common diseases in aging bones: According to the Swiss Osteoporosis Foundation, one in two women and one in four men over 50 will suffer a bone fracture caused by osteoporosis. Patients’ bone material shrinks rapidly, leading to a significantly increased risk of fracture. In clinical research to date, osteoporosis is diagnosed almost exclusively by establishing an overall reduction in bone density. This approach, however, gives little information about the associated, and equally important, local structure and bone density changes. Franz Pfeiffer, TUM professor for Biomedical Physics and head of the research team, has resolved the dilemma: “With our newly developed nano-CT method it is now possible to visualize the bone structure and density changes at high resolutions and in 3D. This enables us to do research on structural changes related to osteoporosis on a nanoscale and thus develop better therapeutic approaches.”
During development, Pfeiffer’s team built on X-ray computed tomography (CT). The principle is well established – CT scanners are used every day in hospitals and medical practices for the diagnostic screening of the human body. In the process the human body is X-rayed while a detector records from different angles how much radiation is being absorbed. In principle it is nothing more than taking multiple X-ray pictures from various directions. A number of such pictures are then used to generate digital 3D images of the body’s interior using image processing.
The newly developed method measures not only the overall beam intensity absorbed by the object under examination at each angle, but also those parts of the X-ray beam that are deflected in different directions – “diffracted” in the language of physics. Such a diffraction pattern is generated for every point in the sample. This supplies additional information about the exact nanostructure, as X-ray radiation is particularly sensitive to the tiniest of structural changes. “Because we have to take and process so many individual pictures with extreme precision, it was particularly important during the implementation of the method to use high-brilliance synchrotron-light and fast, low-noise pixel detectors – both available at the Swiss Light Source (SLS),” says Oliver Bunk, who was responsible for the requisite experimental setup at the PSI synchrotron facility in Switzerland.