Micro-CT essentials: What about temporal resolution?

In this blog series, dr. Wesley De Boever, micro-CT product marketing manager at TESCAN introduces the fundamental principles of micro-CT. In today’s blog post, we consider temporal resolution.

Where spatial resolution (see our previous blog post) describes the ability to resolve features in 2D or 3D space, temporal resolution is the ability to resolve events in time. A practical definition1 for temporal resolution is the time between consecutive measurements or images at the exact same location in space. In 2D microscopic techniques, such as electron microscopy, this is the time it takes to expose and save an image. In micro-CT, an ‘image’ is a 3D dataset, thus the time equivalent to this 2D definition is the time required to perform a full 360 degrees rotation of the sample while acquiring and saving radiographs.

Although scan speed (see this blog post for more information) is important for high temporal resolution, the ability to perform at least two (but preferably hundreds of) fast scans without any gaps in between them. For this, what is truly required is to achieve high temporal resolution. Micro-CT systems with a fast scan speed – such as the TESCAN UniTOM HR and XL – have a temporal resolution of less than 5 seconds, which means events in time can be identified and analyzed with 5 second intervals. Using this high temporal resolution, sudden events such as strut buckling during compression of a metal foam or cell collapse in liquid foams can be captured and observed. Using traditional, slower time-lapse approaches, only larger trends can be observed, and not the small-scale events that cause these trends. This enables researchers to develop better, lighter, cheaper, or stronger materials by optimizing production parameters based on these empirical findings. Fast, dynamic imaging can be used in all sorts of applications, such as studying germination processes in life sciences, the effect of infill patterns in additive manufacturing, the study of flow behavior in earth sciences, or even beer head decay or baking of cookies in food sciences.

It is clear that fast scan speeds—optimum temporal resolution—brings significant advantage, as it ensures that potentially critical events in material will not be left out and will be recorded for future interpretation. But how this is being technically achieved? Obviously, to achieve a high temporal resolution, hardware and software need to be perfectly tuned to each other, ensuring flawless communication over long dynamic experiments. It starts with the rotation stage of the system, which needs to be able to perform hundreds of uninterrupted turns with great precision; the slightest imprecision error would accumulate to a great deviation over hundreds of rotations. Also, the rotation stage needs to be equipped with slip-ring connections to ensure that peripheral equipment such as pumps and compression stages can be controlled without complicated or impossible cable management. Communication with the system’s detector needs to be fine-tuned such that rotation and exposure times are well aligned, enabling accurate reconstruction of all datasets for a time-resolved micro-CT experiment. Finally, tools need to be in place to handle the of data generated during long scanning experiments at high temporal resolution. In this large amount of data, events in time need to be pin-pointed exactly, so that only the most relevant information can be extracted and visualized, without too much overhead. Therefore, software tools such as TESCAN’s AcquilaTM and PantheraTM assure that experiments can be designed and reconstructed. Using a unique Signal-Aided and Sliding Window ReconstructionTM workflow, events in time can be pin-pointed exactly, and only the most relevant information can be extracted and visualized.

Contact us now to learn more about micro-CT imaging at high temporal resolutions!

If you have questions about the Micro-CT portfolio, please do not hesitate to contact your local TESCAN representative!

Wesley De Boever
Product marketing Manager for TESCAN micro-CT