Fig.1: Basic principle of<unk> : superposition free<unk> c cross sections S1 and S2 compared with the (not<unk> c) projected image P Median plane sagittal<unk>  of the head by magnetic resonance imaging.<unk>  is imaging by sections or sectioning that uses any kind of penetrating wave. The method is used in radiology, archaeology, biology, atmospheric science, geophysics, oceanography, plasma physics, materials science, astrophysics, quantum information, and other areas of science. The word<unk>  is derived from Ancient Greek τόμος tomos, "slice, section" and γράφω graphō, "to write" or, in this context as well, "to describe." A device used in<unk>  is called a<unk>  while the image produced is a tomogram. In many cases, the production of these images is based on the mathematical procedure<unk> c reconstruction, such as X-ray computed<unk>  technically being produced from multiple projectional radiographs. Many different reconstruction algorithms exist. Most algorithms fall into one of two categories: filtered back projection (FBP) and iterative reconstruction (IR). These procedures give inexact results: they represent a compromise between accuracy and computation time required. FBP demands fewer computational resources, while IR generally produces fewer artifacts (errors in the reconstruction) at a higher computing cost. Although MRI and ultrasound are transmission methods, they typically do not require movement of the transmitter to acquire data from different directions. In MRI, both projections and higher spatial harmonics are sampled by applying spatially-varying magnetic fields; no moving parts are necessary to generate an image. On the other hand, since ultrasound uses time-of-flight to spatially encode the received signal, it is not strictly a<unk> c method and does not require multiple image acquisitions.
Tomography
X-ray
Tomosynthesis
Angiography
Radiography
Magnetic field imaging
Orthovoltage X-rays
Magnetic Resonance in Medicine