Please introduce yourself and TESCAN SPECTRAL CT.
I am Wesley De Boever, Product Marketing Manager at TESCAN. TESCAN SPECTRAL CT is a smart micro-CT application that delivers non-destructive chemical information from any point inside the sample.
TESCAN offers a portfolio of fast, versatile micro-CT systems, all capable of continuous dynamic micro-CT scanning at very high temporal resolutions. Our solutions can handle samples up to one meter tall and all systems are very versatile, with up to 11 degrees of freedom.
Last year, we launched a new solution,TESCAN SPECTRAL CT, a unique technology that provides 3D compositional information from any point in a sample in a non-destructive manner. It is complementary to the high-quality structural information that you get using micro-CT.
What information does TESCAN SPECTRAL CT provide?
The TESCAN SPECTRAL can provide chemical and structural information at any point inside the sample. It enables the identification of materials, providing contrast where traditional CT cannot, so users can differentiate between materials that cannot be differentiated from traditional CT. Users can also perform absolute identification of unknown materials through K-edge imaging.
What are the principles of SPECTRAL CT and how is it different from conventional CT?
When looking at the principles of SPECTRAL CT, it is important to consider the principles of conventional CT first. In a conventional X-Ray CT system, there is an X-Ray source, a detector and a sample. The X-Ray signal is integrated, removing a lot of information on the composition of materials.
When interacting with different parts of a sample, the resulting X-Ray beam may have a different spectrum. But with conventional CT, we measure overall intensity of the beam, and not the energy-resolved spectrum, , so the compositional information is lost.
By using a spectralCT detector, a direct photon counting detector that is energy sensitive, it is possible to capture the entire spectrum and retrieve some compositional information. We have implemented such a spectral CT detector, combined with a powerful spectral software suite as an add-on to the TESCAN UniTOM XL, TESCAN’s versatile, large-volume, multi-scale micro-CT system.
Tell us about the features of SPECTRAL CT that make it so innovative and versatile.
TESCAN SPECTRAL CT has a fully integrated, novel energy-sensitive photon counting detector that enables users to obtain structural information and non-destructive compositional and chemical data.
Meanwhile, the TESCAN Volume-Of-Interest Scanning (VOIS™) workflow enables users to select locations within that sample, giving them the ability to collect an X-Ray spectrum from any point inside the sample.
The versatility and speed of the TESCAN UniTOM XL micro-CT system enables users to obtain high-quality structural information in short scan times. Further, users receive an intuitive and smooth imaging workflow, with the ability to easily switch between standard and spectral imaging with just a click. No complicated data matching or alignment is required.
Automated K-edge filters, shape analysis and spectrum comparison in the TESCAN SPECTRAL SUITE™ allow users to differentiate between materials, quantify properties and identify compositions, providing powerful tools for reconstructing, visualizing and analyzing spectral data and creating reference libraries.
What is the spatial resolution for the SPECTRAL micro-CT?
SPECTRAL micro-CT is an add-on to our UniTOM XL system. Our UniTOM XL has a maximum resolution of three micrometers and a minimum voxel size of one micrometer. The smallest vox size we can reach with spectral CT is about three or four micrometers, three times less than conventional CT. If you can image something as 10 micrometers with conventional CT, it will be imaged with the same field of view at 30 micrometers with the SPECTRAL CT.
How fast can you collect the spectral data?
It is a little bit slower than conventional CT. If you do a CT scan in one hour, the spectral CT scan will be around two to three hours. Of course, it depends on what you want to see in terms of field of view and resolution.
If you want to do quick point measurements, which is also possible, for example, to identify defects, it can be very fast - a matter of minutes.
What interesting case studies have you done where you have been able to show the benefits of using SPECTRAL CT over conventional CT?
I am going to give you an overview on how SPECTRAL CT can be utilized in the study of polymers.
In conventional micro-CT, contrast is based on density anatomic number. That means that materials with very similar atomic numbers and densities are very hard to differentiate from each other.
This is the case for a particular plastic we used in one of our case studies. The plastics were carbon-based, so they were low atomic number materials with a similar density that looked alike when using conventional CT. SPECTRAL CT was used to greatly increase the contrast and provide information that conventional CT could not.
We did this case study on micro-CT scans of a LEGO® brick sample. We made our own sample out of 36 one by one LEGO® bricks in different colors. Although the LEGO® bricks have different colors in real life, they all look the same in CT scans.
You do not have contrast in a conventional CT scan, as they use an integrated detector and X-Rays are converted first into visible light by a scintillator. It is that visible light that is then detected with a camera sensor. When we looked at a full spectral CT detector, the energy of each photon could be measured. By using the spectral detector, different bricks had different levels of contrast.
Using a specialized training algorithm, we used a spectral CT scan to identify the color of a brick from five different colors. It is not perfect, but we went from one single gray value without any difference to five different classes. We were close to having color CT.
Further, for some images, a particular brick looked brighter. With conventional CT, we could only say that that brick contained an element with a higher atomic number than the other bricks because it looked brighter. With SPECTRAL CT, we could do K-edge analysis, which made it possible to identify the elements that caused the high attenuation.
In our case study, we were able to detect the presence of cadmium in a LEGO® brick. Cadmium is a heavy metal that was used as a stabilizing agent in yellow and red Lego bricks until the 1980s. This meant that using TESCAN SPECTRAL CT, we could even determine information regarding the age of this particular Lego brick.
Have you got anything in mind for future SPECTRAL CT developments?
SPECTRAL CT opens up a range of new possibilities in providing contrast for material identification and the analysis of precious samples. It is completely complementary to conventional CT imaging, offering an additional imaging modality inside a micro-CT scanner.
It is a very novel technology and so there is still much to be explored. This is an open question – if anyone has suggestions or ideas, please reach out. We have several SPECTRAL CT application notes available. Reach out to your local TESCAN representative or have a look at our website: www.tescan.com.
You can register for the full SPECTRAL CT webinar here.
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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