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Is TESCAN’s Spectral CT for Micro-CT Comparable to Energy Dispersive Spectroscopy (EDS) for Scanning Electron Microscopes (SEM)?

When it comes to analytical approaches, TESCAN’s micro-CT and scanning electron microscopy (SEM) share common ground. Both techniques use contrast methods to analyze samples, highlighting features of interest as bright or dark phases.

For some users, images produced by SEM’s backscattered electron detection may be somewhat similar to those from micro-CT (Figure 1), however, those similarities are minimal. The fundamental principles of image acquisition and detection vary significantly between the two methods. In principle, the image and the range of greyscale used to identify specific features and their sizes, shapes, and compositional differences are similar.


Figure 1. Images showing a similar sample containing gold (bright phase), acquired on an SEM (left) and a micro-CT (right)

Until now, the evaluation of the images and volumes acquired by micro-CT relied heavily on the contrast difference alone, while the chemical composition of the identified features remained unknown—unless another instrument had been used. However, TESCAN’s Spectral CT solution is unique because it delivers elemental composition of a sample without the sample ever leaving the micro-CT scanner. Does TESCAN’s Spectral CT solution parallel the established EDS in SEM, a familiar tool within the microscopy community?

Setting aside the intricate technicalities and detection details, let’s consider the common usage of EDS in SEM. In general, a sample, ideally with a flat surface, is brought to the SEM, the area of interest is located based on the electron contrast and then a different detector—EDS detection—is used to unveil elemental composition in the form of a spectrum. The spectrum is then analysed and matched with characteristic spectrum lines of the chemical element.

Spectral CT essentially mirrors the same workflow, with several additional benefits. Firstly, it bypasses the need for sample preparation, whether it's a meter-tall drill core or a small piece of plastic. The sample is scanned in the micro-CT scanner revealing bright and dark phases in 3D. Once the area of interest is identified based on the contrast in the image, spectral detection is used to acquire a spectrum that is analyzed and matched with a spectrum typical for the chemical element. So, the fundamental process and the end results are basically the same.


Spectral vs EDS

Figure 2. Showing point analysis of gold identified through EDS on SEM (left) and Spectral CT on TESCAN UniTOM (right)

In conclusion, while Spectral CT is not technically the same as EDS in SEM, it does follow a similar workflow and provides conclusive insights into the elemental composition of the examined features.

Micro-CT technology stands at the forefront of non-destructive 3D imaging, offering detailed insights into the size, shape and composition of subjects without the need for sample preparation. This multifaceted tool is poised to revolutionize current approaches to material analysis., We can look forward to a future where TESCAN’s spectral capabilities will be as integral to micro-CT analysis as EDS is to SEMs.

TESCAN SPECTRAL CT is available in both the TESCAN UniTOM XL and its smaller counterpart, the CoreTOM. TESCAN SPECTRAL CT can be easily integrated into existing installations. The integration provides a one-click switch from SPECTRAL to conventional imaging, a direct match between the two methods, and a large number of analysis tools to get the most out of SPECTRAL CT data.

To learn more visit info.tescan.com/tescan-spectral-CT


Petr Klímek

Product Marketing Director