Laboratory Developments Related to Full Color X-ray Images
The research of Mini Das’ laboratory at the University of Houston’s Department of Physics was highlighted in a September 2019 Nature Reviews Physics feature article, “X-ray images in full colour.”
Written by Zoe Budrikis, the piece provided an overview of the detector technologies developed at CERN and the capability of producing stunning color X-ray computed tomography images. The article also addressed the challenges of bringing those images to hospitals. Das, who is working to improve the capabilities for these types of detectors, is an associate professor of physics with a joint appointment in the biomedical engineering department.
Das mentors Ph.D. students in both physics and engineering, and all projects in her lab are collaborative interdisciplinary efforts.
The original journal article referred to in the Nature Reviews is: Fredette, Kavuri and Das “Multistep decomposition for spectral computed tomography.” Physics in Medicine and Biology, 64(14)2019. The editors of PMB have made the article free to download for a limited time.
The applications of these physics and engineering developments are in small animal imaging, targeted drug delivery, chemical, biological, materials, and medical imaging.
Excerpt from Nature Reviews Physics: X-ray Images in Full Colour
Other developments in colour X-ray imaging are happening in academia. At the University of Houston, USA, Mini Das works on pushing X-ray imaging technology further in the lab. Writing in Physics in Medicine & Biology, her group recently demonstrated a new method to take the data from a single spectral X-ray image from a photon-counting detector such as Medipix and decompose it into a quantitative map of up to six materials. Most other methods for mapping materials can distinguish two or three materials. The challenge is that even with spectral data, many materials have similar properties. “But you can still find small variations in their behaviour and this is what allows us to distinguish more materials,” says Das. The trick used by her group is to solve the problem in multiple steps, each step focusing on a single material, starting with the most abundant. These techniques may prove useful in performing diagnostic scans with more than one contrast agent, each targeted to a different tissue or disease, as each agent would appear as a different colour, says Das.
Another focus of Das’s research is phase retrieval methods with X-rays. Like visible light bending as it passes from water to air, X-rays bend as they pass from one material to another. However, owing to the short wavelength of X-rays, this bending is tiny. But if the bending is measured, it gives information about the edges of different materials — revealing, for example, the boundary between healthy and diseased tissue. Information about the bending of X-rays is contained in their phase, and so the problem is effectively one of unravelling the effects of absorption and phase variations on an X-ray signal that arrives at the detector. The additional information in spectral X-rays is enough to enable this unravelling, says Das.
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