The researchers from the Technische Universitaet Muenchen (TUM) in
Germany, the Paul Scherrer Institute in Switzerland and the Swiss
Federal Institute of Technology (ETH-Zurich) said osteoporosis is
currently diagnosed almost exclusively by establishing an overall
reduction in bone density. This new method will give much greater
information about the associated local structure and bone density
changes. Until now doctors have been hampered by their lack of
ability to look in detail at changes to bone density.
TUM’s Professor Franz Pfeiffer said this is all about to change.
‘With our newly developed nano-CT [computed tomorgraphy] method it
is now possible to visualise the bone structure and density changes
at high resolutions and in 3D,’ explained Professor Pfeiffer, who
led the research. This will ‘enable us to do research on structural
changes related to osteoporosis on a nanoscale and thus develop
better therapeutic approaches’.
Professor Pfeiffer’s team used X-ray CT to develop its method. CT
scanners are used every day in hospitals and medical practices for
the diagnostic screening of the human body — the 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,’ the authors said. ‘A number of
such pictures are then used to generate digital 3D images of the
body’s interior using image processing.’
The new method measures both the overall beam intensity absorbed by
the object under examination at each angle and the parts of the
X-ray beam that are deflected in different directions or
‘diffracted’. A diffraction pattern is generated for every point in
the sample and this supplies additional information about the exact
nanostructure, as X-ray radiation is particularly sensitive to the
tiniest of structural changes, according to the researchers.
‘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 X-ray radiation
and fast, low-noise pixel detectors,’ said Oliver Bunk, who was
responsible for the experimental setup at the PSI synchrotron
facilities in Switzerland.
The diffraction patterns were then processed using an algorithm
developed by the team, TUM researcher Martin Dierolf stated. ‘We
developed an image reconstruction algorithm that generates a
high-resolution, 3D image of the sample using over 100 000
diffraction patterns,’ he said. ‘This algorithm takes into account
not only classical X-ray absorption, but also the significantly
more sensitive phase shift of the X-rays.’
Roger Wepf, Director of the Electron Microscopy Centre at ETH
Zurich (EMEZ), acknowledged that while ‘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 3D tomography images of bone
samples’.
He said, ‘The new nano-CT procedure also stands out with its high
precision bone density measurement capacity, which is particularly
important in bone research.’ The researchers noted that the method
will open the door to more precise studies on the early phase of
osteoporosis and to the evaluation of the therapeutic outcomes of
various treatments in clinical studies.