German innovation produces sharper x-ray images of soft tissue
German innovators are developing new X-ray technologies. Researchers in Germany are cooperating with counterparts in the US and Sweden to apply a compact, laser-driven synchrotron source to produce X-ray, phase contrast, tomographic images. The technique allows recognition of details in soft tissues, including tumors, which would barely be visible on conventional X-rays.
Scientists at Munich's Technical University (TUM) working on the project used a prototype Compact Light Source (CLS) synchrotron, the world's smallest, to make the structure of soft tissue visible. The team led by Professor Franz Pfeiffer of Department of Biomedical Physics and Physics at TUM, recently demonstrated that the compact synchrotron could generate detailed images of soft tissue.
Pfeiffer says of CLS technology, "Our work demonstrates that we can achieve better results with the Compact Light Source. The CLS allows us to do multimodal tomography scans – a more advanced approach to X-ray imaging."
In conventional X-ray CTs, the difference in brightness or contrast makes one type of tissue distinguishable from another. The absorption of X-rays – the basis for standard CT – is only one way to create contrast. Contrast can, however, also be generated from differences in how tissues change the direction of incoming X-rays, either through bending or scattering X-ray light. These techniques are known respectively as phase-contrast and dark-field CT.
The synchrotrons normally used for high-quality phase-contrast and dark-field imaging are enormous. The CLS is a miniature version of a synchrotron that produces suitable X-rays by colliding laser light with electrons circulating in a desk-sized storage ring. Because it is small and relatively inexpensive, it can be operated in almost any location.
Recently the researchers reported on the first "multimodal" CT scan with the CLS, which simultaneously recorded absorption, phase contrast and dark field. Using a total of 361 two-dimensional X-ray images of an infant mouse taken from different directions, the scientists generated cross-sectional images of the animal.
"The absorption images only show bones and air-filled organs," TUM researcher Elena Eggl says. "However, the phase-contrast and dark-field images reveal much more detail, showing different organs such as the heart and liver. We can even distinguish different types of fat tissue, which is not possible with absorption-based CT scans."
The researchers’ next goal is to use the CLS for phase-contrast and dark-field CT in preclinical studies – an approach that could help visualize cancer. "We work closely together with two clinics to study tumors," Eggl says.
Meanwhile, scientists at the Garching research campus of the TUM and Munich's Ludwig Maximilian University (LMU) are building an improved compact light source and refining the new technique. The German Research Association (DFG) and a number of other regional, European and US sources are funding the project.