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Features and benefits of TEM images
Identification of gastroenteritis viruses with PCR and ELISA can be troublesome due to frequent virus mutation rates, spurred by the hundreds of millions of new infections occurring every year. This problem can be avoided by visually identifying specific virus structures in TEM images. However, conventional TEM analysis is manual and relies heavily on specialists with extensive experience to be able to diagnose quickly and reliably. These persons can identify viruses due to their morphology (shape, size) within minutes irrespective of the virus in question. The problem is that the TEM-based method requires experienced virologists. Hospitals and other diagnostic centers such as national centers for infectious disease control, however, need to have an objective, automatic method for detecting and identifying these viruses.
This is where digital TEM technologies come into play. Using digital TEM image acquisition and analysis, an automated virus detection workflow can be set up. This workflow automates the process of ocular inspection of TEM images, increasing speed and reliability in the diagnostic procedure. Furthermore, it reduces the need for highly trained personnel as manual diagnostic procedures necessitate.
Requirements and challenges
An automated virus identification and analysis system has to fulfill various requirements. This includes fast and simple sample preparation, followed by rapid image acquisition and image analysis with high identification accuracy for differentiating the four different types of viruses responsible for typical gastrointestinal diseases: Astrovirus, Novovirus, Adenovirus or Rotavirus. As Astrovirus and Norovirus are of similar size, as well as Adenovirus and Rotavirus are, they can hence not be distinguished between solely based on sizes. Furthermore, TEM images have a highly structured background and the distinguishing texture features approach the resolution limits.
Image Acquisition
Standard negative staining protocols guarantee completion of TEM sample preparation in less than five minutes. This means that it takes only a few minutes to prepare samples of patients potentially infected with gastro viruses and observe them in the TEM. Controlling all hardware components (microscope, motorized stage, TEM camera) is done efficiently by iTEM, our TEM imaging platform. The software offers numerous real-time functions during image acquisition and ensures acquired images are automatically focused, calibrated and rich in contrast. In addition, iTEM offers many specially developed tools and filters which open up completely new image and data processing opportunities.
Detection, identification and analysis of viruses
The familiar threshold-based segmentation feature runs into limitations when it comes to detecting viruses in highly textured electron micrographs. A robust differentiation of viruses is only possible by analyzing structural features on the surface of the virus. The virus identification software implemented in iTEM Solution Virology is based on an extensive set of structural surface features, derived from virus particles detected. The software contains information of structural features of various virus types drawn from sample images of representative viruses. This information is then used to automatically identify a virus in the TEM image.
Results
This automated virus detection can be performed on viruses causing gastrointestinal diseases. Analysis provides automatic and highly accurate identification of and differentiation between the four common gastroenteritis viruses, i.e. Rota-, Adeno-, Astro-, and Noroviruses. The analytical findings are presented in a written report along with primary analytical data in a format compatible with standard software.
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