Single-shot 3D electron imaging


Rebecca Pool

Wednesday, September 6, 2017 - 15:00
Image: Stereo images of a carbon nanosphere acquired with the tilt-less STEM 3D imaging, [Cécile Hébert/Emad Oveisi/EPFL]
Switzerland-based researchers have unveiled a scanning transmission electron microscopy method that generates fast and reliable 3D images of curvilinear structures without tilting the sample.
Developed by Professor Cécile Hébert, Professor Pascal Fua and colleagues at EPFL, the method can acquire images in a 'single shot', paving the way to studying samples dynamically over time.
Using TEM to reconstruct 3D images usually requires tilting the sample through an arc and imaging  hundreds of views of it, an approach that demands extreme precision to avoid image artifacts. Sophisticated image processing is typically required to to reconstruct the 3D shape.
However, with the latest STEM method, the sample remains stationary while two electron beams, tilted against each other, are directed at the sample, and two detectors are used to record the signal.
Researchers used a FEI Tecnai OSIRIS TEM in scanning mode at an accelerating voltage of 200 kV.
As Hébert highlights: "Instead of rotating the object, we effectively rotate the source and detector."
"Further, by taking advantage of a sophisticated, proprietary image processing algorithm, we reduce the data input required for 3D reconstruction to just two images taken at different incident beam angles, effectively a tilt-less 'stereoscopic pair'," he adds. "This increases the efficiency of data acquisition by one to two orders of magnitude compared to standard TEM tomography techniques."
According to the researchers, their "tilt-less 3D electron imaging" method is well-suited to studying radiation-sensitive, polycrystalline, or magnetic materials.
And because the total electron dose is reduced to a single scan, the method is expected to open up new avenues for real-time 3D electron imaging of dynamic material and biological processes. 
Research is published in Nature Scientific Reports.
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