There is an emerging and relatively recent technology that appears to be an ideal solution for the type of data we produce. Most publications require 2D images or figures. Each of these techniques involves cutting serial sections and either imaging the sample after each cut (FIB and SBFSEM) or the sections themselves (as with serial section TEM).ģD microscopy presents an interesting problem. Scanning electron microscopy also has a range of 3D techniques including FIBSEM (focused ion beam SEM), SBFSEM (serial block face SEM) and array tomography. This essentially recreates a CT scan inside the microscope. Tomography involves taking a series of 2D images and tilting the sample between images over a large range of angles (for example, every 1° over 140° range). Single particle analysis involves taking numerous 2D images of randomly orientated samples (for example, viruses) and analysing their three dimensional structure. Other, more recent, 3D TEM techniques include single particle analysis and tomography. With the advance of computing technology this technique is relatively simply today, although it must have been quite a challenge several decades ago. ![]() The images are combined and a 3D model is built from the data. Several sections of a sample are cut, positioned on a support surface (a grid) and imaged. What is 3D Electron MicroscopyģD electron microscopy was developed for the TEM in the 1950’s using a technique called serial sectioning. SEM results in an image that appears to be three dimensional but doesn’t contain any useful and quantifiable data in the z-axis, even using stereo-paired images (created by tilting the sample slightly between taking two separate images). The beam electrons penetrate into the sample and interact with the atoms, either reflecting the main beam electrons back (backscattered electrons) or exciting atomic electrons, causing them to be emitted (secondary electrons). That spot scans across the surface of an object. Scanning electron microscopes (SEM) use a beam of electrons that is focused to a point or spot. A CCD camera or film records the resultant, x-ray-like image. Electrons are deflected by structures and stains in the sample. Transmission electron microscopes (TEM) shine the beam of electrons through a thin slice (usually 50-70nms thick) of tissue. ![]() Electrons behave in a similar way to light when accelerated through a vacuum and are focused using electro-magnetic lenses. Electron microscopy is an area that has shown a significant boom in 3D imaging.
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