From the Shadows: A New Method for X-Ray Color Imaging

Artistic Representation Showing How an Image Is Created Using the Newly Developed X Ray Imaging Method

Artistic representation showing how an image is created using the newly developed method. Two colors – green and magenta – are emitted by fluorescing atoms in the sample (left) due to X-Ray excitation. The grey round object represents an optic casting a shadow on the detector. The algorithm then produces an actual image with two colors – the intensity of which represents the density of the fluorescing atoms within the sample. Credit: Markus Osterhoff

Researchers at Göttingen University have devised a new technique for X-ray color imaging.

Researchers at the University of Göttingen have created a new approach to generate colored X-ray images. Previously, the only way to determine the chemical composition and arrangement of components in a sample using X-ray fluorescence analysis was to focus X-rays on the entire sample and scan it, which was both time-consuming and costly. The new method allows for the creation of an image of a large area with just one exposure, eliminating the need for focusing and scanning. The findings were published in the journal Optica.

In contrast to visible light, there are no comparably powerful lenses for “invisible” radiation, such as X-ray, neutron, or gamma radiation. However, these types of radiation are essential, for example, in nuclear medicine and radiology, as well as in industrial testing and material analysis.

Uses for X-ray fluorescence include analyzing the composition of chemicals in paintings and cultural artifacts to determine authenticity, origin, or production technique, or the analysis of soil samples or plants in environmental protection. The quality and purity of semiconductor components and computer chips can also be checked using X-ray fluorescence analysis.

For their new method, the scientists used an X-ray color camera developed by PNSensor in Munich and a novel imaging system that essentially consists of a specially structured, gold-coated plate between the object and the detector, which means the sample casts a shadow.

The intensity pattern measured in the detector provides information about the distribution of the fluorescing atoms in the sample, which can then be decoded using a computer algorithm. This new approach means that the plate can be very close to the object or detector, unlike when using an X-ray lens, which makes this a practical method.

“We have developed an algorithm that allows us to quickly and robustly create a sharp image, simultaneously for each X-ray color,” explains first author Dr. Jakob Soltau, a postdoctoral researcher at the Institute for X-ray Physics at the University of Göttingen.

Co-author Paul Meyer, a doctoral student at the same institute, adds: “The optics simply cannot be compared to normal lenses; they were manufactured according to our precise specifications by a new company in Switzerland.”

This start-up company, XRNanotech, specializes in nanostructures and was founded by Dr. Florian Döhring who completed his Ph.D. at Göttingen University. Research group leader Professor Tim Salditt concludes: “Next, we want to extend this approach to three-dimensional imaging of biological samples, as well as exploring phenomena in imaging such as inelastic scattering of X-rays, neutrons, or gamma radiation in nuclear medicine.”

Reference: “Full-field x-ray fluorescence imaging using a Fresnel zone plate coded aperture” by Jakob Soltau, Paul Meyer, Robert Hartmann, Lothar Strüder, Heike Soltau and Tim Salditt, 20 January 2023, Optica.
DOI: 10.1364/OPTICA.477809

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