Image: TUM researchers working together at the micro-computed tomography scanner (Photo courtesy of TUM)
Micro-computed tomography (micro-CT) is an imaging method based on X-ray images which are reconstructed to form a three-dimensional image of the internal structure of samples with small dimensions. Researchers in biomedical physics and biology have significantly improved micro-CT, more specifically imaging with phase contrast and high brilliance X-ray radiation.
Researchers at the Technical University of Munich (TUM, Bavaria, Germany) have developed a new microstructured optical grating and combined it with new analytical algorithms. The new approach makes it possible to depict and analyze the microstructures of samples in greater detail, and to investigate a particularly broad spectrum of samples. Researchers in biology, medicine or material sciences can use this method to obtain information on the structure and characteristics of tissue and material samples which are important in diagnoses and other analyses.
X-ray imaging with phase contrast is particularly well-suited for investigating soft tissue. The method employs the refraction of the X-rays caused by the sample's structures in order to obtain contrast for these structures and thus to depict soft tissue in greater detail than it is possible with conventional X-ray methods. In many phase-contrast methods, optical components modulate the X-rays on their way to the detector, resulting in what is referred to as a diffraction pattern at the detector. Until now inefficient structures such as sandpaper and absorption masks have been used for this type of modulation, but in the meantime a variety of optical gratings are available.
TUM researchers have now introduced a new method for micro-CT with phase contrast using high-brilliance X-ray radiation. The technology is based on a newly developed optical grating referred to as a Talbot Array Illuminator. This new optical element is comparatively easy to produce, is resilient to X-ray radiation and can be used with different energies. This establishes the technically necessary prerequisites for high contrast. The new method enables more efficient use of the radiation dose than with ordinary modulators such as sandpaper and significantly reduces scan times.
The new technology can be used to investigate a particularly broad spectrum of samples. Researchers can even simultaneously depict materials of greatly differing compositions, for example water and oil embedded in stone, which was not possible in the past using conventional methods. This provides crucial advantages over conventional methods not only in medicine and biology, but also opens up new application possibilities in material sciences, for example in geology.
“By combining our newly developed Talbot Array Illuminator with new analysis software optimized for the purpose, we've been able to significantly improve imaging and analysis with micro-CT,” said Julia Herzen, professor of Biomedical Imaging Physics at TUM. “The new technology is more sensitive than comparable methods in this field. At very high resolutions, it allows to depict soft tissue with higher contrast than previously. High sensitivity is particularly important for example in order to detect fine differences within soft tissue.”
"In contrast to previous approaches, our new method also makes quantitative analysis possible. We can make and compare absolute measurements of the electron density of samples, without the need for any assumptions about the samples," added Prof. Herzen.
Technical University of Munich