Revolutionising Imaging: Event-Based Electron Microscopy
An international team of scientists, led by Trinity College Dublin, has devised an innovative imaging method using electron microscopes that significantly reduces the time and radiation required.
Researchers from Trinity College Dublin have introduced a novel imaging technique that could transform disciplines ranging from materials science to medicine. This new method significantly reduces the exposure time and radiation dose required for imaging sensitive materials, including biological tissues.
Traditionally, scanning transmission electron microscopes (STEMs) operate by directing a highly focused beam of electrons across samples, capturing images point by point. At each point, the beam pauses for a fixed time to accumulate signals, akin to cameras using photographic film with constant exposure times. This conventional method, while straightforward, often results in excessive radiation exposure that can damage or destroy samples.
The innovative approach developed by the team revolutionises this process by adopting an event-based detection system. Instead of a fixed observation time and counting detected events, the new method measures the time needed to detect a specific number of events. This shift in methodology is underpinned by a new mathematical theory, demonstrating that the first electron detected at each position provides substantial information, while subsequent detections offer diminishing returns and increase the risk of sample damage.
Images: Example of reduced damage to a human macrophage sample when using TempoSTEM to image versus conventional STEM (Credit: Alexandra Porter (ICL) and Karin Muller (U. Cambridge))
Essentially, this means that illumination can be “shut off” at the peak of imaging efficiency, requiring fewer electrons to achieve high-quality images. To implement this theory practically, the team, in collaboration with IDES Ltd., has patented a technology known as Tempo STEM. This technology incorporates a high-tech “beam blanker” that shutters the beam once the desired precision at each measurement point is reached.
Dr Lewys Jones, Ussher Assistant Professor at Trinity College Dublin’s School of Physics and Funded Investigator in AMBER, led the research team. He highlights the significance of this advancement: “Combining two already state-of-the-art technologies in such an exciting way delivers a real leap in the microscope’s capabilities. Giving microscopists the ability to ‘blank’ or ‘shutter’ the electron beam on and off in a matter of nanoseconds in response to real-time events has never been done before. Our approach reduces the overall dose of radiation needed to produce high-quality images, eliminates the excess dose that was only providing diminishing returns, and avoids causing unnecessary damage to the sample.”
Dr Jon Peters, first author of the study, further elaborated on the implications: “We tend to think of electrons as relatively mild from a radiation perspective, but when they are fired at a tiny biological sample at speeds of around 75% the speed of light, it’s no surprise that they damage these samples. This has been a major issue for microscopy, as the images you get back could be unusable, or worse, misleading. This is obviously problematic if you need to make decisions on future battery materials or catalyst development.”
The new method offers a more efficient and less destructive way to image delicate samples. This can lead to more accurate data and better-informed decisions in fields such as materials science, biology, and medical research.
For further details, you can access the full research paper published in Science.
