In this interview, Wesley De Boever talks to AZoNetwork about spectral CT imaging, and how TESCAN came to be the leading company in spectral CT.
What is spectral CT imaging?
Spectral CT imaging is a type of computed tomography where we measure the X-Ray spectrum that comes out of the source and how it interacts with the sample. So the entire X-Ray spectrum is captured.
How does spectral CT imaging differ from conventional CT imaging?
Spectral CT imaging differs from conventional micro-CT imaging because, in conventional micro-CT imaging, we just measure the difference in intensity of the X-Ray source with and without the sample in the field of view. This means that the system only measures how much of the intensity is lost as it is absorbed by the sample. In spectral CT, you measure what is lost for each different X-Ray energy.
It is important to look at the spectrum rather than just the overall intensity since laboratory X-Ray sources produce a multi-energy X-Ray beam. All of the energies are grouped together in conventional CT, leading to approximations of attenuation and limiting the chemical information you get out of a micro-CT scan. In spectral imaging, you can measure the number of X-Rays before and after the sample for each different energy bin, leading to more and better contrast, and more chemical information.
What information could be provided about a material by spectral CT imaging that conventional CT imaging cannot deliver?
Conventional CT is excellent for providing structural information on a sample. Just by looking at overall attenuation, algorithms can reconstruct the structure to see the porosity of a sample, the size of various features inside, the volume, and so on. However, the user still does not have real information on chemistry: they can only observe a difference in attenuation, which mainly depends on the sample’s atomic number, and this is only shown on a relative scale. If something is brighter, it means it has a higher atomic number than something else, but they will not know what it is.
Spectral CT allows for the absolute identification of materials. For instance, heavy minerals: they have K-edges, which are a spectral signature of an element. By measuring the entire spectrum, these K-edges can be located and the material can be identified as tungsten, gold, platinum, and so on.
But even if these K-edges are not present, different spectra can be compared. This means that materials can be compared with a reference library and then used to identify materials. Another thing that can be done is that numbers can be extracted from images. Once we identify what material is there, we can calculate values like concentration, and density, and calculate or measure the atomic number, and so on.
How does this impact the range of uses for spectral CT imaging?
Where traditional micro-CT was primarily used for structural characterization of samples; now a new dimension has been added to micro-CT. This means that we can add analytical capabilities to micro-CT, to not only characterize materials on the level of the structure, but also on the level of chemistry, composition, density, and so on. This means that the user can now do much more with just one system.
In the past, the user had to complement micro-CT with other techniques: today, a lot more is possible inside the scanner itself. One of the main advantages of spectral micro-CT over other methods is that most alternative methods are 2D surface techniques that cannot analyze what is on the inside of a sample. With spectral micro-CT, the user has these analytical capabilities at any point on the inside of a sample.
Why is this technology emerging now, and what has restricted its development?
Spectral detectors - direct, photon-counting X-Ray detectors - have been around for a long time, but the technology was not at a point where it could be used in a commercial micro-CT scanner. The technology was expensive, the detector pixels were very big, and there were not many pixels in one detector.
Today, the production process of this kind of detector has advanced to the stage where it is finally usable for imaging applications. These detectors are much more complex to make, and the materials are more expensive, so it has taken some time for them to advance to this stage.
How did TESCAN become the first company to market spectral CT imaging?
The researchers at TESCAN have an extensive background in both micro-CT scanner development, and in fundamental micro-CT research. They followed new developments and experimented with spectral CT detectors over the last decade, and know exactly what the pros and cons of the technology are.
These years of experience led to the fact that we are now the first ones to implement spectral CT imaging in a commercial micro-CT system, without compromising on any of the conventional CT capabilities of that system.
Why is the time right for TESCAN to launch this new feature on TESCAN UniTOM XL and TESCAN CoreTOM?
For many years, we have performed experiments with these spectral detectors, and after years of R&D, we finally feel that the time is right and it is possible for us to emerge with a solution that meets all our targets in terms of resolution, speed, price, and ease of use. It can now be re-implemented in a very easy and direct way in our UniTOM XL.
Can you explain how this technology has changed over recent years and what new applications are emerging?
Spectral CT will have a lot of applications in important research fields, such as energy storage applications. This can be seen in the advent of batteries, where we can examine different compounds or the different chemistry of batteries, but also in energy storage in the sense of reservoir characterization for CO2 or hydrogen storage, an important research topic for climate change problematics.
But also for things like recycling, spectral CT can play an important role. A lot of the materials that are in our cell phones have become rarer and rarer, and – particularly in light of all the global changes over the last few years - it is becoming increasingly more difficult to find these materials. This means that recycling will become an increasingly important secondary source for these materials, as we strive to be more sustainable.
Geoscience is another logical application, particularly in the mining of mineral ores: Spectral CT’s added capabilities match very closely to that kind of elemental analysis in an electron microscope.
How has TESCAN's experience assisted in the development of this technology?
The Tescan team has a long history in both traditional micro-CT and very advanced CT applications. This expertise dates from the days when TESCAN XRE was still a spinoff of Ghent University – even then, there were research projects on multi-energy CT imaging. This rich history has allowed us to thrive in the development of our technology and learn from the projects of the past.
We also had a pilot project with a research Institute in Germany for the last four years: the institute is called the Helmholtz Institute, or HZDR, and there we undertook some joint research to develop the technology. This work has been invaluable in the development of our technology.
What is next for TESCAN's spectral CT imaging technology?
Our primary goal now is to take our technology on the road: visiting conferences, promoting the technology and simply explaining how it works to our audience. We are hoping that this direct approach will allow us to talk to a range of people that might benefit from this application.
From this revolutionary technology and its range of applications, we are confident that it will prove useful and significant - particularly for CT users who currently lack this type of capability in their micro-CT research. Meanwhile, our other primary focus is to continue developing the technology. Despite launching the project on our UniTOM XL, our R&D does not stop here. We will always be on the lookout for new detectors and advances in the field of spectral imaging.
What challenges lie ahead for this field, and how is Tescan preparing to tackle them?
The main challenge is that this is a very new technology for the CT community. We are enormously keen to talk to people and to show what the technology can do – something we will achieve by going to the big CT conferences and webinars.
The other challenge, of course, is that it is a new technology for us. Talking to our customers is twofold: it allows them to see the technology’s potential, but it also allows us to learn from them: pinpoint their challenges and reframe our project in that context. This lets us work out how we can best assist our customers and how we can work together on new applications for the technology.
About Wesley de Boever
Wesley de Boever is the Product Marketing Manager for Dynamic Micro-CT at TESCAN. He graduated from Ghent University with a Doctorate in Geology and Earth Science, with a strong focus on multi-scale and multi-technique approaches for structural and chemical characterization of geomaterials. As an expert on 3D characterization, computed tomography and material characterization, he joined TESCAN as an Application Development Specialist before moving on to becoming a Product Marketing Manager specializing in Micro-CT.
This information has been sourced, reviewed and adapted from materials provided by TESCAN USA Inc.
For more information on this source, please visit TESCAN USA Inc.
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