Tomography
![Fig.1: Basic principle of tomography: superposition free tomographic cross sections S1 and S2 compared with the projected image P](/Images/godic/202502/03/TomographyPrinciple_Illustration0147.png")
![Fig.2: Optical coherence tomography of fingertip](/Images/godic/202502/03/HautFingerspitzeOCT0147.gif")
![Fig. 3: Considering a parallel beam irradiation optical system where the angle between the object and all transmission lights equals θ. Here, the numbers in the figure (see the numbers within the parentheses) respectively indicate: (1) = an object; (2) = the parallel beam light source; (3) = the screen; (4) = transmission beam; (5) = the datum circle; (6) = the origin; and (7) = a fluoroscopic image (a one-dimensional image; pθ(s)). Two datum coordinate systems xy and ts are also imagined in order to explain the positional relations and movements of features (0)–(7) in the figure. In addition, a virtual circle centered at the above-mentioned origin (6) is set on the datum plane (it will be called “the datum circle” henceforth). This datum circle (6) will be represents the orbit of the parallel beam irradiation optical system. In the figure above, X-Y plane rotates around the point of origin in the plane in such a way “to keep mutual positional relationship between the light source (2) and screen (7) passing through the trajectory (5).” Rotation angle of this case is defined as θ. In the figure set out above, absorption coefficient at a cross-sectional coordinate (x, y) of the subject is modeled as μ(x, y).](/Images/godic/202502/03/CT_PRINCI_PB0148.jpg")
Tomography refers to imaging by sections or sectioning, through the use of 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 sciences. In most cases it is based on the mathematical procedure called tomographic reconstruction.