An introduction to low dose electron tomography- from specimen preparation to data collection

Electron tomography is a technique that uses a Transmission Electron Microscope (TEM) to determine a three-dimensional (3D) structure from any given asymmetric object [1]. This process can be simply broken down into 3 steps. First, a series of two dimension projection images of the specimen are recorded and systematically tilted to different angles in the microscope. Second, these individual images are aligned to a common origin. Finally, the projections are then backprojected to create a 3D representation of the sample [2]. Modern commercial instruments now provide a computerized interface, which has been exploited to develop software for automated data collection of the tilt series. As a result, electron tomography is growing in popularity. Before attempting to collect data for tomography it is important to note that the resolution of the data will depend on specimen preparation, imaging conditions and image processing. In this review we attempt to address two of the important issues in electron tomography namely biological specimen preparation and imaging conditions. The reader is directed to Frank 2006 [3] for a comprehensive overview of the current data processing methods.