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Electron tomography is an extension of traditional transmission electron microscopy and uses a transmission electron microscope to collect the data. In the process, a beam of electrons is passed through the sample at incremental degrees of rotation around the center of the target sample.
In contrast to other electron tomography techniques, samples are imaged under cryogenic conditions (< −150 °C). For cellular material, the structure is immobilized in non-crystalline, vitreous ice , allowing them to be imaged without dehydration or chemical fixation , which would otherwise disrupt or distort biological structures.
For example, different elements in a sample result in different electron energies in the beam after the sample. This normally results in chromatic aberration – however this effect can, for example, be used to generate an image which provides information on elemental composition, based upon the atomic transition during electron-electron ...
A scanning transmission electron microscope (STEM) is a type of transmission electron microscope (TEM). Pronunciation is [stɛm] or [ɛsti:i:ɛm]. Pronunciation is [stɛm] or [ɛsti:i:ɛm]. As with a conventional transmission electron microscope (CTEM), images are formed by electrons passing through a sufficiently thin specimen.
Electron beam computed tomography (EBCT) is a fifth generation computed tomography (CT) scanner in which the X-ray tube is not mechanically spun in order to rotate the source of X-ray photons. This different design was explicitly developed to better image heart structures that never stop moving, performing a complete cycle of movement with each ...
This technique is called electron tomography. One of the difficulties with high resolution transmission electron microscopy is that image formation relies on phase contrast. In phase-contrast imaging , contrast is not intuitively interpretable, as the image is influenced by aberrations of the imaging lenses in the microscope.
The E-T secondary electron detector can be used in the SEM's back-scattered electron mode by either turning off the Faraday cage or by applying a negative voltage to the Faraday cage. However, better back-scattered electron images come from dedicated BSE detectors rather than from using the E–T detector as a BSE detector.
Reproduction of an early electron microscope constructed by Ernst Ruska in the 1930s. Many developments laid the groundwork of the electron optics used in microscopes. [2] One significant step was the work of Hertz in 1883 [3] who made a cathode-ray tube with electrostatic and magnetic deflection, demonstrating manipulation of the direction of an electron beam.